Quantification of nerve fiber layer thickness in normal and glaucomatous eyes using optical coherence tomography

Comparison between GDx VCC scanning laser polarimetry and Stratus OCT optical coherence tomography in the diagnosis of chronic glaucoma

PURPOSE

To compare the abilities of scanning laser polarimetry with the variable corneal compensator (GDx VCC) with those of optical coherence tomography (Stratus OCT) in discriminating between healthy and early-to-moderate perimetric glaucomatous eyes.

METHODS

A total of 95 glaucomatous patients (mean deviation - 3.7 +/- 3.0 dB, pattern standard deviation 4.5 +/- 2.7 dB) and 62 control subjects underwent imaging by the GDx VCC and Stratus OCT using both optic nerve head (ONH) and retinal nerve fibre layer (RNFL) scan protocols. One eye per patient was considered. Sensitivity at > or = 90% specificity and area under the receiver operating characteristic curve (AROC) were calculated for each GDx VCC and Stratus OCT index.

RESULTS

The largest AROCs with Stratus OCT were associated with cup : disc area ratio (0.88) for ONH scan indices, and with average thickness (0.84) for RNFL scan indices. The nerve fibre indicator provided the greatest AROC for the GDx VCC indices (0.85).

CONCLUSIONS

Both the GDx VCC and Stratus OCT instruments were shown to be useful in the detection of glaucomatous damage. The best performing indices for the GDx VCC and Stratus OCT with both ONH and RNFL scans gave similar AROCs, showing a moderate sensitivity in early-to-moderate glaucoma patients.

Retinal nerve fibre layer thickness profile in normal eyes using third-generation optical coherence tomography

AIMS

To establish four normal retinal nerve fibre layer (RNFL) thickness radial profiles based on third-generation optical coherence tomography (OCT) and to compare them with previously reported histologic measurements.

METHODS

A total of 20 normal eyes were studied. A circular scan was adjusted to the size of the optic disc and three scans were performed with this radius and every 200 microm thereafter, up to a distance of 1400 microm. Four different radial sections (superotemporal, superonasal, inferonasal, and inferotemporal) were studied to establish RNFL thickness OCT profiles. Additionally, two radial scans orientated at 45 and 135 degrees crossing the optic disc centre were performed in six of 20 eyes, and RNFL thickness was measured at disc margin.

RESULTS

Quadrant location and distance from disc margin interaction in RNFL thickness was statistically significant (P<0.001). The RNFL thickness decreased (P<0.001) as the distance from the disc margin increased for all sections. The measurements automatically generated by the OCT built-in software were thinner (P<0.001) than histologic ones close to the disc margin.

CONCLUSIONS

Four normal OCT RNFL profiles were established and compared with histological data obtained from the same area. RNFL measurements assessed by OCT 3 were significantly thinner close to the optic disc margin.

Nerve fiber layer thickness in glaucoma patients with asymmetric hemifield visual field loss

PURPOSE

To investigate the presence of retinal nerve fiber layer (RNFL) thinning and determine the relationship between RNFL thickness and visual field sensitivity loss in glaucoma patients with asymmetric hemifield visual field loss.

PATIENTS AND METHODS

Thirty glaucoma patients with asymmetric hemifield visual field loss and 30 normal control subjects were included in the study. RNFL thickness was measured by optical coherence tomography and visual field sensitivity was measured by automated perimetry. Glaucoma patients with advanced visual field loss restricted to 1 hemifield and early or absent glaucomatous field loss in the other hemifield on the basis of the visual field data were included. Visual field sensitivity and mean deviation (MD) were averaged separately in each of the 2 hemifields. The hemifields in each eye were categorized as early (MD>or=-6 dB) and advanced (MD<-6 dB) glaucomatous hemifields.

RESULTS

RNFL thickness measurements in corresponding (eg, superior peripapillary quadrant with inferior hemifield) advanced glaucomatous hemifields (59+/-16 microm) were significantly (P<0.001) lower than in corresponding early glaucomatous hemifields (90+/-25 microm). The mean RNFL thickness in corresponding advanced and early glaucomatous hemifields were significantly lower than in normal control subjects (P<0.0001). On the basis of the normative database supplied by optical coherence tomography software, 100% and 43% of eyes had abnormal RNFL thickness in corresponding advanced and early glaucomatous hemifields, respectively. A linear correlation was found between RNFL thickness and MD in the early (r=0.6; P<0.001) and advanced (r=0.5; P=0.007) glaucomatous hemifields.

CONCLUSIONS

RNFL thinning was present in corresponding hemifields of glaucomatous eyes with minimal visual field defect and correlated with visual field sensitivity loss. Measurement of RNFL thickness has potential for detection of early nerve fiber loss owing to glaucoma.

Influence of pupil size and cataract on retinal nerve fiber layer thickness measurements by Stratus OCT

AIM

To investigate whether retinal nerve fiber layer (RNFL) thickness, as measured by optical coherence tomography (OCT), is influenced by pupil size and cataract.

METHODS

RNFL thickness was measured by means of Stratus OCT (RNFL Thickness 3.4 acquisition protocol) in a group of consecutive patients undergoing phacoemulsification and intraocular lens implantation. Measurements were taken preoperatively without pupil dilation (PR1), preoperatively with pupil dilation (PR2), and 1 month postoperatively without pupil dilation.

RESULTS

Twenty-five eyes of 25 patients were enrolled in the study and underwent statistical analysis. Pupil dilation caused RNFL thickness measurements to increase slightly in PR2 compared with PR1; the difference showed to be statistically significant in the 360-degree average measurement (P=0.0456) and in the nasal quadrant (P=0.032), but not in the remaining quadrants. Postoperative measurements were higher than those of PR1 in all quadrants (temporal P=0.011; superior P=0.0098; nasal P<0.0001; inferior P=0.0081) and in 360 degrees average (P<0.0001), suggesting that the presence of cataract significantly influences RNFL thickness as measured by Stratus OCT. More advanced degrees of lens opacity were correlated to a higher decrease in RNFL thickness values (r=0.4071, P=0.0434).

CONCLUSIONS

While pupil size only marginally affects RNFL measurements performed by Stratus OCT, the presence and degree of cataract seem to have a significant impact. This effect should be taken in consideration when using this technology for the diagnosis of glaucoma and other neuro-ophthalmologic disorders possibly affecting the RNFL.

Reproducibility of Peripapillary Retinal Nerve Fiber Layer and Macular Retinal Thickness Measurements Using Optical Coherence Tomography

We investigated the interoperator reproducibility of peripapillary retinal nerve fiber layer (RNFL) and macular retinal thickness measurements using optical coherence tomography (OCT) in healthy Taiwanese eyes. In this study, OCT-3 was used by three trained and experienced operators to measure peripapillary RNFL and macular retinal thickness in a randomly chosen single eye from each normal subject. Mean thickness levels and the differences in thickness measurements among the three operators were calculated and compared. The eyes of 39 subjects (24 females and 15 males) were enrolled. The mean age of the subjects was 30.4 +/- 16.1 years (range, 11-46 years). The mean pupil diameter after pupillary dilation was 7.4 +/- 0.6mm (range, 6-9 mm). Comparing peripapillary RNFL and macular retinal thickness measurements after pupillary dilation, there were no significant differences in: superior, inferior, temporal, and nasal peripapillary areas; 6 mm total macular volume and foveal thickness; and 1, 3 and 6 mm perifoveal areas among the three operators. In this study, OCT thickness measurements showed good interoperator reproducibility among three trained and experienced operators.

Optical coherence tomography versus automated perimetry for follow-up of optic neuritis

PURPOSE

To evaluate the usefulness of optical coherence tomography (OCT) for follow-up of optic neuritis (ON) compared with subjective visual function tests.

METHODS

Twelve patients with ON underwent a complete ophthalmological evaluation at initial diagnosis, including best corrected visual acuity (VA), visual fields testing and OCT examination. These examinations were repeated periodically over 6 months. Retinal nerve fibre layer (RNFL) thickness evolution was analysed and correlated with VA and visual field mean deviation.

RESULTS

Six months after ON, mean RNFL in the affected eye decreased significantly compared with that in the fellow eye (24.54%). A significant correlation was found between RNFL thinning and final VA (r = 0.807, p = 0.005), with a 1-line drop in VA for every 5.4-micro m decrease. All patients with an altered visual field had an abnormal RNFL value; of the seven patients with normal visual fields, 57% had an abnormal RNFL value (p < 5%).

CONCLUSIONS

Optical coherence tomography can detect axonal damage as early as the third month after an isolated initial episode of ON, even in the presence of normal visual fields. Mean RNFL thinning is correlated with final VA.

Humphrey matrix frequency doubling technology perimetry and optical coherence tomography measurement of the retinal nerve fiber layer thickness in both normal and ocular hypertensive subjects

PURPOSE

The purpose of this study was to determine by means of the Humphrey Matrix frequency doubling technology (FDT) perimetry and the optical coherence tomography (OCT) retinal nerve fiber layer (RNFL) thickness measurement whether functional and/or structural differences exist between normal and ocular hypertensive (OHT) subjects.

PATIENTS AND METHODS

One eye of 60 consecutive normal individuals and 60 OHT subjects was enrolled in this prospective observational comparative case series study. All subjects were examined at either the Ophthalmology Clinic, University of Chieti-Pescara, Chieti, Italy or the Department of Ophthalmology, S. Maria della Misericordia Hospital, Udine, Italy. All subjects underwent a full ophthalmic examination, including visual acuity, slit-lamp biomicroscopy, central corneal thickness ultrasound pachymetry measurement, achromatic automated perimetry, Matrix FDT perimetry, stereoscopic optic nerve head photography, and OCT. Matrix FDT perimetry mean deviation (MD), pattern standard deviation, glaucoma hemifield test, and 12 OCT RNFL thickness parameters were examined. Student t test, Bonferroni correction for multiple comparisons and receiver operator characteristics curve areas (AUROCs) were used to find any discrimination function between healthy and OHT eyes. Sensitivities at 83% and 92% specificities were reported.

RESULTS

The FDT MD scores ranged from -1.10 to +3.80 decibels (db) in normal individuals and from -4.75 to +3.20 db in OHT subjects. The comparison between the average MD in the 2 groups showed a statistically significant difference (P=0.024). OCT showed a statistically significant difference between the 2 groups when examining the ratio between the inferior and the superior mean RNFL thickness (P=0.004). For OCT, the parameter with the largest AUROC for discriminating between healthy and hypertensive eyes was the ratio between the mean inferior and superior RNFL thickness (AUROC=0.85, sensitivity=75% at specificity=83%, sensitivity=67% at specificity=92%). For Matrix FDT perimetry, the parameter with the largest AUROC was MD (AUROC=0.78, sensitivity=67% at specificity=83%, sensitivity=58% at specificity=92%).

CONCLUSIONS

Our results suggest that OHT eyes having a normal achromatic automated perimetry and a normal clinical disc appearance cannot be differentiated from normal eyes using conventional OCT parameters. When analyzing the ratio between inferior and superior average RNFL thickness, however, a significant difference is evident between healthy and hypertensive eyes. Using Matrix FDT perimetry, a significant difference in MD seems to exist between these 2 groups of eyes. The AUROCs confirm that OCT Iavg/Savg and Matrix FDT MD show the greatest sensitivity and specificity among the examined OCT and Matrix FDT parameters.

Quantifying axonal loss after optic neuritis with optical coherence tomography

OBJECTIVE

To determine to what degree changes in retinal nerve fiber layer (RNFL) thickness after optic neuritis (ON) correlate with either visual recovery or impairment.

METHODS

ON can cause visible defects within the RNFL, which can be quantified using optical coherence tomography (OCT). It may be possible to predict visual recovery by measuring RNFL loss after ON. Fifty-four patients underwent repeated evaluations with optical coherence tomography and standardized ophthalmic testing after ON. Regression analyses were used to determine the relationship between RNFL thickness and visual function.

RESULTS

Thinning of the RNFL was seen in the majority of patients (74%), and it tended to occur within 3 to 6 months of ON. The average RNFL value was thinner (p<0.0001) in the affected (78 microm) compared with the unaffected eye (100 microm). Patients with incomplete visual recovery demonstrated greater RNFL loss after ON. Regression analyses demonstrated a threshold of RNFL thickness (75 microm), below which RNFL measurements predicted persistent visual dysfunction.

INTERPRETATION

Determination of RNFL thickness may predict visual recovery after ON, and lower RNFL values correlate with impaired visual function. Optical coherence tomography may have a potential role as a surrogate marker for axonal integrity within the optic nerve among patients with ON.

Logistic Regression Analysis for Glaucoma Diagnosis Using Stratus Optical Coherence Tomography

PURPOSES

The purposes of this study are to investigate the diagnostic performance of logistic regression analysis (LRA) applied to multidimensional information on glaucoma disease and to determine the area under receiver operator characteristic curves (AROCs) for differentiating between normal and glaucomatous eyes in the Taiwan Chinese population based on the summary data from the Stratus Optical Coherence Tomography (OCT).

METHODS

One randomly selected eye from each of the 89 patients with glaucoma and from each of the 88 age- and gender-matched normal individuals were included in the study. Nine glaucomatous eyes and eight normal eyes were excluded as a result of poor OCT scans. Finally, 80 normal eyes and 80 glaucomatous eyes (mean deviation, -4.5 +/- 4.12 dB) were analyzed. The whole dataset was split into four equal sets. Each set combines 20 patients with glaucoma and 20 normal individuals. Fourfold crossvalidation was conducted. Retinal nerve fiber layer thickness and optic nerve head were measured by Stratus OCT in each patient. Twenty-five OCT parameters were included in a LRA method to determine the best combination of parameters for discriminating between glaucomatous and healthy eyes based on AROCs.

RESULTS

With the LRA method, the AROC for glaucoma detection was 0.911 with sensitivity at 80% and 90% specificity were 83.7% and 80.0%, respectively.

CONCLUSIONS

Compared with the OCT-provided parameters, the LRA method improved the ability to differentiate between normal and glaucomatous eyes in the Taiwan Chinese population.

Modelling the normal retinal nerve fibre layer thickness as measured by Stratus optical coherence tomography

BACKGROUND

The variation in retinal nerve fibre layer thickness (RNFLT) as measured by Stratus optical coherence tomography (OCT) in healthy subjects may be reduced when the effect on RNFLT measurements of factors other than disease is corrected for, and this may improve the diagnostic accuracy in glaucoma. With this perspective we evaluated the isolated and combined effects of factors potentially affecting the Stratus OCT RNFLT measurements in healthy subjects.

METHODS

We included 178 healthy eyes of 178 subjects between 20 and 80 years of age. Participants underwent an extensive eye examination. Stratus OCT RNFLT was measured by three standard protocols, two with high and one with standard image resolution. Effects on RNFLT of age, gender, refractive error, axial length, lens nuclear colour and opalescence, intra-ocular pressure (IOP), and optic disc size were examined by univariate and multivariate analyses.

RESULTS

Age, refractive error, axial length, and lens nuclear colour and opalescence affected RNFLT in univariate analyses, whereas gender, IOP, and optic disc size had no significant effect. In multivariate analyses only age in combination with refractive error, or with axial length, was significant and explained 14.7-17.6% (R2) of the total variation of RNFLT, approximately 50% more than age alone. RNFLT decreased by 2.6-2.9 microm per increasing decade of age and increased by 1.5-1.8 microm per more positive diopter of spherical equivalent using full-circle measurements of the three standard protocols. These effects varied between measurement sectors.

CONCLUSIONS

RNFLT as measured by Stratus OCT standard protocols was significantly affected by age and refractive status. The effect on global RNFLT of a difference in refractive error of 10 diopters corresponded to the effect of a difference in age of 60 years. Theoretically, the effect of refractive status may be explained by artefacts of RNFLT measurement circle placement. The results suggest that the diagnostic accuracy of Stratus OCT may be improved by considering refractive status in addition to age when RNFLT is measured. For this purpose spherical equivalent seems as effective as axial length.

Correlation Between Topographic Profiles of Localized Retinal Nerve Fiber Layer Defects as Determined by Optical Coherence Tomography and Red-Free Fundus Photography

PURPOSE

To evaluate the topographic relationship of localized retinal nerve fiber layer (RNFL) defects as determined by optical coherence tomography (OCT) and by red-free fundus photography.

METHODS

Sixty-five eyes of 65 patients with localized, wedge-shaped RNFL defects identified in red-free fundus photographs and with matching visual field defects were scanned with the Stratus OCT. On the resulting RNFL thickness report printout, segments of the line graph outside of the 95 and 99% normal limits were defined as "5% OCT defect" and "1% OCT defect," respectively. Correlations between the angular location and angular width of RNFL defects as determined by OCT (OCT defects) and by red-free fundus photography (red-free defects) were evaluated.

RESULTS

Angular locations and widths of both 5 and 1% OCT defects were significantly correlated with corresponding red-free defects (all P values<0.001).

CONCLUSIONS

There is a strong topographic correlation between characteristics of localized RNFL defects as determined by OCT and red-free photography.

Optical Coherence Tomography of the Optic Nerve Head

PURPOSE

Optical coherence tomography may be a new technique for quantitative 3-dimensional assessment of the optic nerve head for diagnosis of optic nerve anomalies and diseases such as the glaucomas. The purpose of the present study was to examine its reproducibility.

PATIENTS AND METHODS

The clinical noninterventional study included 10 randomly chosen eyes of 10 healthy individuals who underwent 24 optical coherence tomographic examinations with the high-resolution and fast scan program, interactively corrected or uncorrected. The pupils were not dilated. All examinations were performed by 3 examiners independently of one another. The coefficient of variation was calculated as the ratio of the mean of the standard deviations divided by the mean of the means.

RESULTS

The coefficients of variation for redetermination of optic disc area, ranging between 0.047 and 0.119, were lowest for the manually corrected fast scan mode and highest for the uncorrected fast scan mode. For remeasurements of the neuroretinal rim area, the best mean coefficient of variation was 0.073+/-0.026 (corrected fast scan mode).

CONCLUSIONS

In healthy eyes, the morphometric measurements of the optic nerve head by optical coherence tomography show a relatively high reproducibility with mean coefficients of variation lower than 10% for remeasurements of the optic disc and neuroretinal rim area. With undilated pupils, reproducibility is better with the fast scan mode with interactive correction of the outlining of the optic disc border than it is with the high-resolution mode.

Optical coherence elastography of engineered and developing tissue

Biomechanical elastic properties are among the many variables used to characterize in vivo and in vitro tissues. Since these properties depend largely on the micro- and macroscopic structural organization tissue, it is crucial to understand the mechanical properties and the alterations that occur tissues respond to external forces or to disease processes. Using a novel technique called coherence elastography (OCE), we mapped the spatially distributed mechanical displacements strains in a representative model of a developing, engineered tissue as cells began to proliferate attach within a three-dimensional collagen matrix. OCE was also performed in the complex tissue of the Xenopus laevis (African frog) tadpole. Displacements were quantified a cross-correlation algorithm on pre- and postcompression images, which were acquired using coherence tomography (OCT). The images of the engineered tissue were acquired over a 10-development period to observe the relative strain differences in various regions. OCE was able differentiate changes in strain over time, which corresponded with cell proliferation and matrix as confirmed with histological observations. By anatomically mapping the regional variation stiffness with micron resolution, it may be possible to provide new insight into the complex by which engineered and natural tissues develop complex structures.

Peripapillary retinal nerve fiber layer thickness variations with myopia

PURPOSE

To determine the relationship between peripapillary retinal nerve fiber layer (RNFL) thickness and myopia using optical coherence tomography (OCT).

DESIGN

Prospective observational case series.

METHODS

One hundred thirty-two young males with myopia (spherical equivalent [SE], -0.50 to -14.25 diopters) underwent ophthalmic examination of one randomly selected eye. Optical coherence tomography (OCT-1, version 4.1) was performed by a single operator using circular scans concentric with the optic disc with scan diameters of 3.40 mm, 4.50 mm, and 1.75 x vertical disc diameter (VDD). For each scan diameter, mean peripapillary RNFL thickness was calculated. Statistical analysis comprised repeated-measurements analysis and Pearson correlation.

RESULTS

Mean peripapillary RNFL thickness did not correlate with SE for the 3.40-mm (r = -0.11, P = 0.22), 4.50-mm (r = -0.103, P = 0.24), or 1.75xVDD (r = -0.08, P = 0.36) OCT scan diameters. Neither did mean peripapillary RNFL thickness correlate with axial length for the 3.40-mm (r = -0.04, P = 0.62), 4.50-mm (r = 0.03, P=0.75), or 1.75xVDD (r = -0.02, P = 0.78) scan diameters. Mean peripapillary RNFL thicknesses for the 3.40-mm, 4.50-mm, and 1.75xVDD scans were 101.1+/-8.2 microm (95% confidence interval [CI], 99.4-102.8), 78.9+/-8.2 microm (95% CI, 77.5-80.3), and 97.5+/-10.9 microm (95% CI, 95.6-99.4), respectively.

CONCLUSIONS

Mean peripapillary RNFL thickness did not vary with myopic SE or axial length for any OCT scan diameter investigated. Retinal NFL thickness measurements may be a useful parameter to assess and monitor glaucoma damage in myopic subjects.

Retinal assessment using optical coherence tomography

Over the 15 years since the original description, optical coherence tomography (OCT) has become one of the key diagnostic technologies in the ophthalmic subspecialty areas of retinal diseases and glaucoma. The reason for the widespread adoption of this technology originates from at least two properties of the OCT results: on the one hand, the results are accessible to the non-specialist where microscopic retinal abnormalities are grossly and easily noticeable; on the other hand, results are reproducible and exceedingly quantitative in the hands of the specialist. However, as in any other imaging technique in ophthalmology, some artifacts are expected to occur. Understanding of the basic principles of image acquisition and data processing as well as recognition of OCT limitations are crucial issues to using this equipment with cleverness. Herein, we took a brief look in the past of OCT and have explained the key basic physical principles of this imaging technology. In addition, each of the several steps encompassing a third generation OCT evaluation of retinal tissues has been addressed in details. A comprehensive explanation about next generation OCT systems has also been provided and, to conclude, we have commented on the future directions of this exceptional technique.

Retinal nerve fiber layer assessment using optical coherence tomography with active optic nerve head tracking

PURPOSE

To develop an eye-motion-tracking optical coherence tomographic (OCT) method and assess its effect on image registration and nerve fiber layer (NFL) thickness measurement reproducibility.

METHODS

A system capable of tracking common fundus features based on reflectance changes was integrated into a commercial OCT unit (OCT II; Carl Zeiss Meditec, Inc., Dublin, CA) and tested on healthy subjects and patients with glaucoma. Twenty successive peripapillary NFL scans were obtained with tracking and 20 without tracking, for 40 images in each session for each eye. Subjects participated in one session on three different days. Composite OCT scans and composite fundus images were generated for assessment of eye tracking. NFL thickness measurement reproducibility was also assessed.

RESULTS

Seven healthy and nine glaucomatous eyes of 16 subjects were recruited. A qualitative assessment of composite OCT scans and composite fundus images showed little motion artifact or blurring along edges and blood vessels during tracking; however, those structures were less clearly defined when tracking was disengaged. There was no significant reproducibility difference with and without tracking in both intra- and intersession NFL measurement SD calculations in any location. The mean retinal pixel SD was significantly smaller with tracking than without (490.9 +/- 19.3 microm vs. 506.4 +/- 31.8 microm, P = 0.005, paired t-test).

CONCLUSIONS

A retinal-tracking system was successfully developed and integrated into a commercial OCT unit. Tracking OCT improved the consistency of scan registration, but did not influence NFL thickness measurement reproducibility in this small sample study.

Electrophysiological assessment of glaucomatous visual dysfunction during treatment with cytidine-5'-diphosphocholine (citicoline): a study of 8 years of follow-up

In this study we assessed, by simultaneous recordings of visual evoked potentials (VEPs) and pattern-electroretinograms (PERGs), the effects cytidine-5'-diphosphocholine (citicoline) on retinal function and/or visual cortical responses in glaucoma patients. Thirty glaucoma patients were randomly divided into two age-matched groups: patients in group GC (15 patients) were treated with citicoline (1,000 mg/die intramuscularly) for 2 months; patients in group GP (15 patients) were treated with placebo for 2 months. After 4 months of wash-out (month 6), GC patients underwent a further 2-month period of citicoline treatment (months 7-8) followed by another 4-month period of wash-out (months 9-12). In GP patients the wash-out was extended for a further 6 months (months 7-12). During the following 13-96 months, GC patients received additional 2-month periods of treatment with citicoline (each period followed by 4 months of wash-out) for a total of 16 periods in 8 years. GP patients were also examined at months 24, 26, 48, 60, 72, 84 and 96. In GC patients the first two treatments with citicoline induced a significant (p <0.01) improvement of VEP and PERG parameters with respect to pre-treatment conditions. VEPs and PERGs recorded in GC patients after the first wash-out revealed that, although there was a worsening trend, the electrophysiological improvement was still maintained with respect to baseline conditions. The additional periods of citicoline treatment in GC patients during the subsequent 13-96 months induced a greater (p <0.01) improvement of VEP and PERG parameters with respect to pre-treatment conditions and when compared to GP patients. Thus, we observed that citicoline significantly improves retinal and cortical bioelectrical responses in glaucoma patients, suggesting a potential use of this substance in the medical treatment of glaucoma, as a complement to hypotensive therapy.

Glaucoma in children: are we making progress?

BACKGROUND

Glaucoma in children presents difficult clinical challenges. Even when appropriately treated, blindness can occur.

DESIGN

Retrospective interventional case series and literature review.

METHODS

All clinical records of children seen by the author with a diagnosis of glaucoma established before 16 years of age were reviewed from 1977 to 2003. Glaucoma was classified as primary infantile, aphakic, syndrome-related, and secondary. The best-corrected visual acuity, refractive error, configuration of the optic nerve cup, and perimetry were recorded. The intraocular pressure (IOP) for each visit was recorded. IOP measurements of 19 mm Hg or less were considered "good." The percentage of "good" readings was calculated for each eye. Representative visual acuities, refractive errors, IOP, disk configuration, and perimetry were recorded at 6, 12, 18, and 24 years of age for each patient. The admitting ophthalmologic diagnosis for each child at the Western Pennsylvania School for Blind Children was recorded from 1887 to 2003.

RESULTS

One hundred twenty-six children (204 eyes) were studied: infantile glaucoma, 52 eyes; aphakic glaucoma, 40 eyes; syndrome associated, 69 eyes; and secondary glaucoma, 43 eyes. The mean follow-up was 11.6 years (1 to 30 years). Overall, 60 (29.4%) of 204 eyes had a 6/12 (20/40) or better corrected visual acuity at the most recent visit. The percentage with this acuity remained stable throughout the follow-up period. Eyes with infantile glaucoma had the best acuity, and 40% had 6/12 (20/40) or better. Amblyopia was common and responded to treatment. Eyes with aphakic glaucoma had the worst acuity with only 10% achieving 6/12 or better. These eyes had a bimodal onset of glaucoma; eyes with an early onset had an angle closure configuration and eyes with a delayed onset had an open angle. Early cataract removal and microcornea were risk factors for glaucoma. If the IOP was maintained at 19 mm Hg or less (good) on 80% of the determinations over time, the optic nerve cup compared with the diameter of the optic nerve (C/D ratios) were stable. Eight patients had multiple, good quality, visual fields performed over 3 to 15 years. If the patients had "good" IOP on 70% of the measurements, the visual fields remained stable. A historical perspective of glaucoma control was gained by looking at the admitting diagnosis at the Western Pennsylvania School for Blind Children. From 1910 to 1970, an average of 9.2 children blind due to glaucoma were admitted each decade. From 1971 to 2003, there were only three children with glaucoma admitted over 30 years.

CONCLUSION

Removal of congenital cataracts should be delayed until 3 to 4 weeks of age. Consideration should be given for using 19 mm Hg or less to measure the success of glaucoma treatment in children. Treatment of amblyopia is as important as IOP control in children. Imaging technology such as optical coherence tomography and measurement of central corneal thickness may play an important future role in the assessment of children with suspected or known glaucoma.

Detection of early diabetic change with optical coherence tomography in type 2 diabetes mellitus patients without retinopathy

PURPOSE

To detect early diabetic damage in type 2 diabetes mellitus patients with no diabetic retinopathy (NDR) using optical coherence tomography (OCT) and to evaluate OCT as a clinical test.

METHODS

Thirty-two patients with NDR (n = 32) were enrolled. We examined retinal and retinal nerve fiber layer (RNFL) thickness using OCT. Two healthy normal populations were also enrolled for the retinal thickness (n = 48) and RNFL thickness (n = 34). Both OCT measurements were obtained in four areas (temporal, superior, nasal and inferior). The receiver operator characteristic (ROC) curve was generated to evaluate the predictor variables.

RESULTS

Comparing the normal and NDR eyes, retinal thickness significantly increased (p = 0.03) and RNFL thickness significantly decreased (p = 0.02) in the superior areas. The area under the ROC curve was 0.65 for the superior retinal thickness and 0.63 for the superior RNFL thickness.

CONCLUSIONS

Both OCT measurements can detect early retinal damage in NDR patients.

Comparison of retinal nerve fiber layer thickness and optic disk algorithms with optical coherence tomography to detect glaucoma

PURPOSE

To compare the performance of the retinal nerve fiber layer (RNFL) thickness and optic disk algorithms as determined by optical coherence tomography to detect glaucoma.

DESIGN

Observational cross-sectional study.

METHODS

setting: Academic tertiary-care center. study population: One eye from 42 control subjects and 65 patients with open-angle glaucoma with visual acuity of > or =20/40, and no other ocular pathologic condition. observation procedures: Two optical coherence tomography algorithms were used: "fast RNFL thickness" and "fast optic disk." main outcome measures: Area under the receiver operating characteristic curves and sensitivities at fixed specificities were used. Discriminating ability of the average RNFL thickness and RNFL thickness in clock-hour sectors and quadrants was compared with the parameters that were derived from the fast optic disk algorithm. Classification and regression trees were used to determine the best combination of parameters for the detection of glaucoma.

RESULTS

The average visual field mean deviation (+/-SD) was 0.0 +/- 1.3 and -5.3 +/- 5.0 dB in the control and glaucoma groups, respectively. The RNFL thickness at the 7 o'clock sector, inferior quadrant, and the vertical C/D ratio had the highest area under the receiver operating characteristic curves (0.93 +/- 0.02, 0.92 +/- 0.03, and 0.90 +/- 0.03, respectively). At 90% specificity, the best sensitivities (+/-SE) from each algorithm were 86% +/- 3% for RNFL thickness at the 7 o'clock sector and 79% +/- 4% for horizontal integrated rim width (estimated rim area). The combination of inferior quadrant RNFL thickness and vertical C/D ratio achieved the best classification (misclassification rate, 6.2%).

CONCLUSION

The fast optic disk algorithm performs as well as the fast RNFL thickness algorithm for discrimination of glaucoma from normal eyes. A combination of the two algorithms may provide enhanced diagnostic performance.

Relationship between the s-wave amplitude of the multifocal electroretinogram and the retinal nerve fiber layer thickness in glaucomatous eyes

PURPOSE

To determine whether a significant correlation exists between the amplitude of the s wave of the multifocal electroretinogram (mfERG) and the retinal nerve fiber layer thickness (RNFLT) in glaucomatous eyes.

METHODS

Twenty-three eyes of 23 patients with glaucoma were studied. In all eyes, the severity of the defects in the upper visual field differed significantly from the severity of those in the lower half. Patients having visual field halves with mean deviation (MD) values lower than -5 dB were placed in group A, and patients having visual field halves with MD values greater than -5 dB were placed in group B. The mfERGs were elicited by 37 stimulus elements alternating from white to black in a pseudorandom binary m-sequence at a frequency of 9.4 Hz. The mfERGs in the upper and lower visual field halves were summed to yield upper and lower averaged waves. The GDx variable corneal compensator and optical coherence tomography were used to measure the RNFLT.

RESULTS

The retinal nerve fiber layer was significantly thinner in group A than in group B. There was a significant correlation between the RNFLT and the MD values of visual field defects. The s-wave amplitude was significantly smaller in group A than in group B. The s-wave amplitude also correlated significantly with the MD and the RNFLT.

CONCLUSION

The significant correlations between the s-wave amplitude and the MD, and between the s-wave amplitude and the RNFLT, indicate that the s-wave receives significant contributions from the retinal ganglion cells and their axons.

Early Detection of Thinning of Retinal Nerve Fiber Layer in Glaucomatous Eyes by Optical Coherence Tomography 3000: Analysis of Retinal Nerve Fiber Layer Corresponding to the Preserved Hemivisual Field

The retinal nerve fiber layer (RNFL) thickness was measured with the optical coherence tomography using version 3.0 software (OCT3000) in 153 eyes of 153 normal subjects. The mean of the average RNFL thickness over the entire 360 degrees in the control group was 92.5 +/- 12.9 microm which was significantly thinner than the normative data of 95.9 +/- 11.4 microm included with the OCT3000 (p < 0.01). The RNFL thickness decreased with increasing age (p < 0.01, r = -0.395). The RNFL thickness was also measured in 53 eyes of 53 patients with glaucoma whose superior (13 eyes) or inferior (40 eyes) perimetric hemifields were normal. Only the RNFL thickness corresponding to the preserved perimetric hemifields were measured by OCT3000 and scanning laser ophthalmoscopy (SLO). The RNFL thickness in the superior and inferior 30 degrees sectors, the maximum and average RNFL thickness in the superior (S(max) and S(avg)), and inferior quadrants (I(max) and I(avg)) were analyzed. The S(max), S(avg), I(max), I(avg), and the RNFL thickness in the superior (p < 0.05), superotemporal and inferotemporal sectors (p < 0.01) in the glaucoma patients without a nerve fiber layer defect (SLO) were significantly thinner than in the control subjects in same age. OCT3000 measurements showed that the RNFL thickness in glaucomatous eyes with normal perimetric visual fields and SLO was significantly thinner than the RNFL thickness in normal eyes.

Comparison of retinal nerve fibre layer measurements using optical coherence tomography versions 1 and 3 in eyes with band atrophy of the optic nerve and normal controls

AIMS

To compare retinal nerve fibre layer (RNFL) measurements were carried out with two different versions of an optical coherence tomography device in patients with band atrophy (BA) of the optic nerve and in normal controls.

METHODS

The RNFL of 36 eyes (18 with BA and 18 normals) was measured using an earlier version of an optical coherence tomography device (OCT-1). The measurements were repeated using a later version of the same equipment (OCT-3), and the two sets of measurements were compared.

RESULTS

Using OCT-1, the peripapillary RNFL thickness (mean+/-SD, in microm) in eyes with BA measured 80.42+/-6.94, 99.81+/-14.00, 61.69+/-13.02, 101.70+/-12.54, and 57.36+/-16.52 corresponding to the total RNFL average, superior, temporal, inferior, and nasal quadrants, respectively. Using OCT-3, the corresponding measurements were 63.11+/-6.76, 81.22+/-13.34, 39.50+/-8.27, 86.72+/-15.16, and 45.05+/-8.03. Each of these measurements was significantly smaller with OCT-3 than with OCT-1. In normal eyes, RNFL average and temporal quadrant OCT-3 values were significantly smaller than OCT-1 values, but there was no significant difference in measurements from the superior, inferior, and nasal quadrant.

CONCLUSIONS

RNFL measurements were smaller with OCT-3 than with OCT-1 for almost all parameters in eyes with BA and in the global average and temporal quadrant measurements in normal eyes. Investigators should be aware of this fact when comparing old RNFL measurement with values obtained with later versions of the equipment.

Exploration of the retinal nerve fiber layer thickness by measurement of the linear dichroism

An electro-optic device mounted on a slit lamp to assess the degree of polarization of a light beam that has double passed through the retina about the optic-nerve head in the living human eye is described. The asymmetric structure of the retinal nerve's fiber layer possesses a linear-form dichroism and will partially polarize an unpolarized light beam that is scattered at the fundus of the eye and has double passed the ocular media (cornea, lens, retina). This partial polarization is a function of the retinal nerve's fiber layer thickness, and its measurement may be used for exploring glaucoma and other retinal neuropathies. Experimental conditions allow us to neglect corneal dichroism. The first clinical measurements show a different degree of polarization between normal and glaucomatous eyes and a good correlation with the results obtained by optical coherence tomography.

Posterior pole retinal thickness in ocular hypertension and glaucoma: early changes detected by hemispheric asymmetries

PURPOSE

To evaluate retinal thickness at the posterior pole of the fundus in ocular hypertension (OHT) and open-angle glaucoma (OAG), and to correlate morphometric findings with visual sensitivity as determined by automated perimetry.

METHODS

One randomly selected eye from 41 patients with clinical diagnosis of OHT (n = 25) or early to moderate OAG (n = 16) and 16 age-matched normal controls was examined. Retinal thickness was measured by Retinal Thickness Analyzer (RTA), acquiring 5 pre-defined scans covering the central 20 degrees of the fundus. RTA average thickness and thickness profile data, including hemispheric asymmetries calculated as relative (superior/inferior and nasal/temporal) or absolute (vertical and horizontal, ie, independent of which hemisphere was thinner) parameters, were calculated. For each eye, white-on-white Humphrey 30-2 visual field results were analyzed, in addition to standard global indices, by quantifying perimetric sensitivities for regions of the posterior pole corresponding to those sampled by the RTA.

RESULTS

On average, central retinal thickness was reduced (P < 0.05) in OAG compared with OHT or normal control eyes. Vertical hemispheric absolute thickness asymmetry was increased (P < or = 0.01) in OAG eyes compared with the other groups. Horizontal hemispheric absolute thickness asymmetry was increased (P < 0.01) in both OHT and OAG eyes, compared with control eyes. At least one of the RTA parameters was altered in 13 of 25 OHT (52%) and 12 of 16 OAG eyes (75%), most frequently involving thickness asymmetries. In OAG, but not OHT eyes, superior/inferior asymmetry was positively (r = 0.69, P < 0.01) correlated with the corresponding asymmetry in perimetric sensitivity.

CONCLUSIONS

The RTA can reveal increased hemispheric thickness asymmetries in both OHT and OAG eyes. In OAG eyes thickness asymmetries are associated with corresponding perimetric asymmetries. The findings in OHT eyes suggest that localized anatomic and functional damage to inner retina may not develop in parallel early in the disease process.

Three-dimensional retinal imaging with high-speed ultrahigh-resolution optical coherence tomography

PURPOSE

To demonstrate high-speed, ultrahigh-resolution, 3-dimensional optical coherence tomography (3D OCT) and new protocols for retinal imaging.

METHODS

Ultrahigh-resolution OCT using broadband light sources achieves axial image resolutions of approximately 2 microm compared with standard 10-microm-resolution OCT current commercial instruments. High-speed OCT using spectral/Fourier domain detection enables dramatic increases in imaging speeds. Three-dimensional OCT retinal imaging is performed in normal human subjects using high-speed ultrahigh-resolution OCT. Three-dimensional OCT data of the macula and optic disc are acquired using a dense raster scan pattern. New processing and display methods for generating virtual OCT fundus images; cross-sectional OCT images with arbitrary orientations; quantitative maps of retinal, nerve fiber layer, and other intraretinal layer thicknesses; and optic nerve head topographic parameters are demonstrated.

RESULTS

Three-dimensional OCT imaging enables new imaging protocols that improve visualization and mapping of retinal microstructure. An OCT fundus image can be generated directly from the 3D OCT data, which enables precise and repeatable registration of cross-sectional OCT images and thickness maps with fundus features. Optical coherence tomography images with arbitrary orientations, such as circumpapillary scans, can be generated from 3D OCT data. Mapping of total retinal thickness and thicknesses of the nerve fiber layer, photoreceptor layer, and other intraretinal layers is demonstrated. Measurement of optic nerve head topography and disc parameters is also possible. Three-dimensional OCT enables measurements that are similar to those of standard instruments, including the StratusOCT, GDx, HRT, and RTA.

CONCLUSION

Three-dimensional OCT imaging can be performed using high-speed ultrahigh-resolution OCT. Three-dimensional OCT provides comprehensive visualization and mapping of retinal microstructures. The high data acquisition speeds enable high-density data sets with large numbers of transverse positions on the retina, which reduces the possibility of missing focal pathologies. In addition to providing image information such as OCT cross-sectional images, OCT fundus images, and 3D rendering, quantitative measurement and mapping of intraretinal layer thickness and topographic features of the optic disc are possible. We hope that 3D OCT imaging may help to elucidate the structural changes associated with retinal disease as well as improve early diagnosis and monitoring of disease progression and response to treatment.

Macular Symmetry Testing For Glaucoma Detection

PURPOSE

To evaluate structural asymmetry in the macula using optical coherence tomography (OCT) in glaucomatous eyes with visual field defects localized to one hemifield.

METHODS

Complete examination, standard automated perimetry (SAP), and OCT imaging (512 A-scans) of the peripapillary retina and macula were performed. Exclusion criteria were visual acuity <20/40, diseases other than glaucoma, and SAP defects localized to both hemifields. Macular OCT images were obtained using four 5-mm radial scans centered on the foveola and passing obliquely through the macula (15 degrees superotemporally and inferotemporally). Macular measurements temporal to the fovea (T) were sub-divided into nasal (T1) and temporal (T2) segments. Macular symmetry testing (MST) was performed in T, T1, and T2 segments by comparing the mean macular thickness of the perimetrically abnormal and perimetrically normal hemi-zones (macular thickness in perimetrically normal hemi-zone/macular thickness in perimetrically abnormal hemi-zone x 100), and superior and inferior hemi-zones in normal subjects (macular thickness in superior hemi-zone/macular thickness in inferior hemi-zone x 100). MST measurements were considered to be abnormal if they exceeded the 95% limits of normal variability.

RESULTS

Forty eyes of 40 patients (20 normal, 20 glaucoma) were enrolled (mean age 60 +/- 19 years, range 21-89). All eyes with glaucoma had associated hemifield defect (average MD = -7.23 +/- 4.8 dB, range -0.9 to -15.4). In glaucomatous eyes, mean retinal thickness in T, T1, and T2 within the perimetrically abnormal hemi-zone (222 +/- 14 microm, 224+/- 17 microm, 221 +/-13 microm, respectively) was significantly less (P = 0.002, 0.008, 0.001, respectively) than the corresponding segments in the perimetrically normal hemi-zone (235 +/- 17 microm, 237 +/- 18 microm, 233 +/- 17 microm, respectively). Normal eyes showed no difference (P = 0.17, 0.20, 0.35) in T, T1, and T2 measurements within the superior hemi-zone (254 +/- 11, 249 +/- 14, 258 +/- 14) and inferior hemi-zone (252 +/- 11, 250 +/- 13, 255 +/- 13), respectively. MST values in glaucomatous eyes were outside 95% limits of normal variability in 17/20 (85%) T segments, 16 /20 (80%) T1 segments, and 16/20 (80%) T2 segments.

CONCLUSION

Localized macular thickness changes exist in glaucomatous eyes with regional visual field loss. The MST may represent a novel strategy for glaucoma diagnosis.

Morphometric assessment of normal, suspect and glaucomatous optic discs with Stratus OCT and HRT II

AIMS

To compare morphometric parameters and diagnostic performance of the new Stratus Optical Coherence Tomograph (OCT) Disc mode and the Heidelberg Retina Tomograph (HRT); to evaluate OCT's accuracy in determining optic nerve head (ONH) borders.

METHODS

Controls and patients with ocular hypertension, glaucoma-like discs, and glaucoma were imaged with OCT Disc mode, HRT II, and colour disc photography (DISC-PHOT). In a separate session, automatically depicted ONH shape and size in OCT were compared with DISC-PHOT, and disc borders adjusted manually where required. In a masked fashion, all print-outs and photographs were studied and discs classified as normal, borderline, and abnormal. The Cohen kappa method was then applied to test for agreement of classification. Bland-Altman analysis was used for comparison of disc measures.

RESULTS

In all, 49 eyes were evaluated. Automated disc margin recognition failed in 53%. Misplaced margin points were more frequently found in myopic eyes, but only 31/187 were located in an area of peripapillary atrophy. Agreement of OCT with photography-based diagnosis was excellent in normally looking ONHs, but moderate in discs with large cups, where HRT performed better. OCT values were consistently larger than HRT values for disc and cup area. Compared with HRT, small rim areas and volumes tended to be minimized by OCT, and larger ones to be magnified.

CONCLUSIONS

Stratus OCT Disc protocol performed overall well in differentiating between normal and glaucomatous ONHs. However, failure of disc border recognition was frequently observed, making manual correction necessary. ONH measures cannot be directly compared between HRT and OCT.

Comparison of ultrahigh- and standard-resolution optical coherence tomography for imaging macular pathology

OBJECTIVE

To compare ultrahigh-resolution optical coherence tomography (UHR OCT) with standard-resolution OCT for imaging macular diseases, develop baselines for interpreting OCT images, and identify situations where UHR OCT can provide additional information on disease morphology.

DESIGN

Cross-sectional study.

PARTICIPANTS

One thousand two eyes of 555 patients with different macular diseases including macular hole, macular edema, central serous chorioretinopathy, age-related macular degeneration (AMD), choroidal neovascularization, epiretinal membrane, retinal pigment epithelium (RPE) detachment, and retinitis pigmentosa.

METHODS

A UHR ophthalmic OCT system that achieves 3-microm axial image resolution was developed for imaging in the ophthalmology clinic. Comparative studies were performed with both UHR OCT and standard 10-microm-resolution OCT. Standard scanning protocols of 6 radial 6-mm scans through the fovea were obtained with both systems. Ultrahigh-resolution OCT and standard-resolution OCT images were correlated with standard ophthalmic examination techniques (dilated ophthalmoscopy, fluorescein angiography, indocyanine green angiograms) to assess morphological information contained in the images.

MAIN OUTCOME MEASURES

Ultrahigh-resolution and standard-resolution OCT images of macular pathologies.

RESULTS

Correlations of UHR OCT images, standard-resolution images, fundus examination, and/or fluorescein angiography were demonstrated in full-thickness macular hole, central serous chorioretinopathy, macular edema, AMD, RPE detachment, epiretinal membrane, vitreal macular traction, and retinitis pigmentosa. Ultrahigh-resolution OCT and standard-resolution OCT exhibited comparable performance in differentiating thicker retinal layers, such as the retinal nerve fiber, inner and outer plexiform, and inner and outer nuclear. Ultrahigh-resolution OCT had improved performance differentiating finer structures or structures with lower contrast, such as the ganglion cell layer and external limiting membrane. Ultrahigh-resolution OCT confirmed the interpretation of features, such as the boundary between the photoreceptor inner and outer segments, which is also visible in standard-resolution OCT. The improved resolution of UHR OCT is especially advantageous in assessing photoreceptor morphology.

CONCLUSIONS

Ultrahigh-resolution OCT enhances the visualization of intraretinal architectural morphology relative to standard-resolution OCT. Ultrahigh-resolution OCT images can provide a baseline for defining the interpretation of standard-resolution images, thus enhancing the clinical utility of standard OCT imaging. In addition, UHR OCT can provide additional information on macular disease morphology that promises to improve understanding of disease progression and management.

Custom measurement of retinal nerve fiber layer thickness using STRATUS OCT in normal eyes

PURPOSE

To evaluate variability of retinal nerve fiber layer (RNFL) thickness measurements in normal eyes and their correlation with optic disc diameter by using two different scan options of the ultimate commercial optical coherence tomography (OCT) unit (STRATUS OCT, Carl Zeiss Meditec, Inc., Dublin, CA).

METHODS

In this observational case series and instrument validation study 30 eyes of 30 normal subjects were enrolled. Each eye underwent optic disc vertical diameter measurement by means of both stereoscopic photography and planimetry and OCT; RNFL thickness measurements were performed using OCT. Three repetitions of two series of scans were performed. Each eye was scanned at two different options (RNFL thickness 3.4 and Nerve Head Circle). For each option descriptive statistics, analysis of variance, intraclass correlation coefficients (ICCs), and coefficients of variation (COVs) were calculated. To verify the correlation between the two methods of optic disc diameter assessment and to study the influence of optic disc diameter on RNFL measurement using the two different OCT options, Pearson's correlation coefficients were calculated.

RESULTS

Optic disc diameter length ranged from 1.47 to 2.04 mm (mean 1.709 mm, SD +/- 0.147) with stereoscopic photographs, and from 1.47 to 2.02 mm (mean 1.703 mm, SD +/- 0.143) with OCT (Pearson correlation coefficient 0.999, p<0.001). Mean RNFL thickness was 89.29 mm (SD +/- 10.80 mm) using the RNFL thickness 3.4 scanning option and 89.88 mm (SD +/- 1.72 mm) using the Nerve Head Circle protocol (Pearson correlation coefficient 0.065, p=0.734). The intersubject variance is higher using the RNFL thickness 3.4 option than using the NHC protocol (sum of square: 1,014,760 vs. 25,741) (p<0.001); the intrasubject variance is very similar in the two groups (2,372 vs 2,360) (p=NS). The ICC is 99.89% when using the RNFL thickness 3.4 option, 95.62% with the NHC protocol (p=NS). COVs were 12.10% and 1.91% by using RNFL thickness 3.4 and Nerve Head Circle option, respectively. Pearson's correlation coefficient was 0.988 (p<0.001) when comparing optic disc diameter and RNFL thickness by using the RNFL thickness 3.4 option and -0.016 (p=0.932) when comparing optic disc diameter and RNFL thickness by using the Nerve Head Circle option.

CONCLUSIONS

These results suggest that both scan options give good RNFL thickness measurement reproducibility; the use of the Nerve Head Circle option leads to less interindividual variability and can minimize the effect of differences in optic disc diameter on RNFL thickness measurements in normal subjects.

Macular thickness reduction in eyes with unilateral optic atrophy detected with optical coherence tomography

AIMS

To assess the changes in macular and peripapillary retinal nerve fibre layer (RNFL) thickness in eyes with unilateral optic atrophy and to evaluate the relationship between retinal thickness and visual function.

METHODS

Enrolled were 22 patients with unilateral optic atrophy. Macular thickness at the divided nine areas and peripapillary RNFL thickness in quadrantic sections were measured by optical coherence tomography. Thickness values in the affected eyes were compared with those in the contralateral unaffected eyes. The correlation of foveal thickness with best-corrected visual acuity (BCVA) was evaluated. The correlation between retinal thickness and the remaining visual field area circumscribed with I-4-e isopter in superior and inferior hemifield was assessed.

RESULTS

Macular thinning was observed in all areas (P < 0.001 in each area) other than the fovea (P = 0.068). Peripapillary RNFL thickness decreased in all quadrantic sections (P < 0.001 in each section). The affected to unaffected eye ratio of retinal thickness was more than 0.6 in each area. BCVA did not correlate with foveal thickness (correlation coefficient = 0.094, P = 0.668). Although not statistically significant (P = 0.281, superior hemifield; P = 0.053, inferior hemifield), there was a tendency that eyes with severe visual field loss show more marked retinal thinning.

CONCLUSIONS

Macular thinning with the preserved foveal thickness is a hallmark of eyes with optic atrophy. Together with no correlation between foveal thickness and BCVA, this finding would help in differential diagnosis of macular and optic nerve diseases.

Comparison of glaucomatous parameters in normal, ocular hypertensive and glaucomatous eyes using optical coherence tomography 3000

This study was performed to evaluate optic disc appearance, retinal nerve fiber layer (RNFL) thickness, and macular thickness in normal, ocular hypertensive (OHT) and glaucomatous eyes using optical coherence tomography (OCT) 3000. One hundred fifty-eight eyes of 167 consecutive subjects were enrolled: 60 normal, 53 OHT, and 54 glaucomatous. OCT topographic parameters of cup diameter, cup area, rim area, and cup/disc area ratio were significantly less in OHT eyes than in normal eyes and were significantly less in glaucomatous eyes than in normal and OHT eyes. RNFL was significantly thinner in OHT eyes than in normal eyes in the inferior quadrant, and in glaucomatous eyes than in OHT and normal eyes in the mean and for all four quadrants. Macular thickness was significantly thinner in glaucomatous eyes than in OHT and normal eyes throughout all subdivisions. Optic disc parameters, and RNFL and macular thickness measurements made with OCT may be useful in the clinical assessment of glaucoma.

Optical coherence tomography of the retinal nerve fibre layer in mild papilloedema and pseudopapilloedema

AIMS

To determine the degree to which optical coherence tomography (OCT) can distinguish differences in retinal nerve fibre layer (RNFL) thickness between eyes with mild papilloedema, pseudopapilloedema, and normal findings.

METHODS

13 patients with mild papilloedema, 11 patients with congenitally crowded optic nerves, and 17 normal subjects underwent neuro-ophthalmic examination, automated visual field testing, and fundus photography. Spinal fluid pressure measurements were obtained in a subgroup of five patients with pseudopapilloedema and 11 patients with mild papilloedema. Circular OCT scans using a diameter of 3.38 mm surrounding the optic disc were performed in each eye of patients and subjects. Fundus photographs were analysed by two observers who diagnosed crowding or papilloedema and graded amounts of swelling. Findings were assessed by descriptive statistics and variance analysis.

RESULTS

RNFL thickness was greater in the superior and inferior quadrants and showed a high degree of correlation between each group of patients and subjects. A statistically significant difference was found in mean RNFL thickness between both groups of patients with optic disc swelling and normal subjects. However, there was not a statistical difference in mean nerve fibre layer thickness between patients with papilloedema and those with congenitally crowded optic nerves.

CONCLUSIONS

OCT demonstrates measurable differences in nerve fibre layer thickness between normal subjects and patients with either papilloedema or pseudopapilloedema. However, OCT does not appear to differentiate between those individuals with congenitally crowded optic nerves and those with mild papilloedema caused by increased intracranial pressure.

the impact of definition of primary open-angle glaucoma on the cross-sectional assessment of diagnostic validity of Heidelberg retinal tomography

PURPOSE

To evaluate the impact of different definitions of primary open angle glaucoma (POAG) on assessment of the diagnostic validity of Heidelberg Retinal Tomography (HRT).

DESIGN

Retrospective, cross-sectional study.

METHODS

A search of medline (1992-2003) led to the retrieval of 181 papers containing definitions of POAG, including the eight visual field (VF)-based definitions used for this study. A sample of 193 normal subjects, 222 patients with suspected POAG, and 103 with POAG underwent HRT and the 24 II Humphrey VF examinations to assess the diagnostic validity of HRT. POAG was defined on the basis of Glaucoma Hemifield Test (GHT) "out of normal limits" associated with corrected pattern standard deviation (CPSD) > 2 dB and intraocular pressure (IOP) > or =22 mm Hg. The VFs were re-analyzed and categorized according to the other eight definitions of POAG: IOP formed part of all the definitions, whereas the appearance of the optic disk did not. The sensitivity and specificity of each scenario were calculated by standard procedures.

RESULTS

The definitions of POAG found in the literature included 17 IOP criteria, more than 15 optic disk criteria, and more than 30 VF criteria. The sensitivity of HRT ranged from 0.51 to 0.80, and its specificity from 0.94 and 0.95 when the patients with suspected POAG were excluded; diagnostic validity was much lower and still variable when the POAG suspects were included with the normal or the POAG groups.

CONCLUSIONS

The most commonly used VF-based definitions of POAG led to substantial differences in the sensitivity and specificity of HRT when using the same large sample of normal subjects and POAG patients. A standard definition of POAG is needed to make diagnostic investigations more accurate and comparable.

Optical coherence tomography longitudinal evaluation of retinal nerve fiber layer thickness in glaucoma

OBJECTIVES

To longitudinally evaluate optical coherence tomography (OCT) peripapillary retinal nerve fiber layer thickness measurements and to compare these measurements across time with clinical status and automated perimetry.

METHODS

Retrospective evaluation of 64 eyes (37 patients) of glaucoma suspects or patients with glaucoma participating in a prospective longitudinal study. All participants underwent comprehensive clinical assessment, visual field (VF) testing, and OCT every 6 months. Field progression was defined as a reproducible decline of at least 2 dB in VF mean deviation from baseline. Progression of OCT was defined as reproducible mean retinal nerve fiber layer thinning of at least 20 mum.

RESULTS

Each patient had a median of 5 usable OCT scans at median follow-up of 4.7 years. The difference in the linear regression slopes of retinal nerve fiber layer thickness between glaucoma suspects and patients with glaucoma was nonsignificant for all variables; however, Kaplan-Meier survival curve analysis demonstrated a higher progression rate by OCT vs VF. Sixty-six percent of eyes were stable throughout follow-up, whereas 22% progressed by OCT alone, 9% by VF mean deviation alone, and 3% by VF and OCT.

CONCLUSIONS

A greater likelihood of glaucomatous progression was identified by OCT vs automated perimetry. This might reflect OCT hypersensitivity or true damage identified by OCT before detection by conventional methods.

Discrimination between normal and glaucomatous eyes using Stratus optical coherence tomography in Taiwan Chinese subjects

BACKGROUND

We differentiated between normal and glaucomatous eyes in the Taiwan Chinese population based solely on the quantitative assessment of summary data reports from Stratus optical coherence tomography (OCT) by comparing their area under the receiver operating characteristic (ROC) curve.

METHODS

One randomly selected eye from each of the 62 patients with early glaucomatous damage (mean deviation -2.8 +/- 1.8 dB) and from each of the 62 age- and sex-matched normal individuals were included in the study. Measurements of glaucoma variables (retinal nerve fiber layer thickness and optic nerve head analysis results) were obtained by Stratus OCT. Twenty-one OCT parameters were included in a linear discriminant analysis (LDA) using forward selection and backward elimination to determine the best combination of parameters for discriminating between glaucomatous and healthy eyes based on ROC curve area.

RESULTS

The average RNFL thickness was the best individual parameter for differentiating between normal eyes and glaucomatous eyes (ROC curve area 0.793). The maximum area under the ROC curve of six input parameters (average RNFL thickness; 10, 11, and 12 o'clock segment thicknesses; cup area; and vertical integrated rim area) generated by the forward selection method was 0.881. Whereas the maximum area under the ROC curve of 15 input parameters (average RNFL thickness; 1, 3, 4, 6, 8-10, 12 o'clock segment thicknesses; vertical integrated rim area; horizontal integrated rim area; disc area; cup to disc area ratio; cup to disc horizontal ratio; and cup to disc vertical ratio) generated by backward elimination method was 0.929.

CONCLUSIONS

The performance of individual parameters obtained from Stratus OCT is fairly reliable for differentiating the early glaucomatous eyes from normal eyes. However, the discriminant power increases when LDA with forward selection and backward elimination methods is applied.

Correlation of endoscopic optical coherence tomography with histology in the lower-GI tract

BACKGROUND

Optical coherence tomography (OCT), a noninvasive optical imaging technique, provides high-resolution cross-sectional images of tissue microstructure. We developed a system for real-time endoscopic OCT (EOCT) of the human GI tract. During clinical trials, the structure of mucosa and submucosa, glands, blood vessels, pits, villi, and crypts was observed in a range of GI organs. Although EOCT images are thought to accurately depict actual histologic features, there are few data to support this assumption. Therefore, the present study correlated images acquired with an EOCT imaging system in vitro to corresponding histologic sections.

METHODS

EOCT images were obtained of fresh specimens of ileum, colon, and rectum that then were fixed in formalin and were processed for microscopic evaluation by using standard methods. The thickness of mucosa and of submucosa was determined for both EOCT images and histologic slides.

RESULTS

The first hyper-reflective layer in the EOCT images was identified as mucosa. A close correlation (R 2=0.84) was observed between EOCT and histology. Furthermore, the submucosa and the muscularis propria could be identified as the next deepest hyporeflective band and a hyper-reflective layer, respectively, in EOCT images. The submucosa was found to be more compressible than mucosa, and its EOCT appearance was dependent on its content of adipose tissue.

CONCLUSIONS

EOCT provides images that precisely correlate with the histologic structure of the mucosa and the submucosa of the GI tract.

Optical Coherence Tomography Measurement of the Retinal Nerve Fiber Layer in Normal and Juvenile Glaucomatous Eyes

The aim of this study was to quantitatively assess and compare the thickness of the retinal nerve fiber layer (RNFL) in normal and glaucomatous eyes of children using the optical coherence tomograph. The mean RNFL thickness of normal eyes (n=26) was compared with that of glaucomatous eyes (n=26). The eyes were classified into diagnostic groups based on conventional ophthalmological physical examination, Humphrey 30-2 visual fields, stereoscopic optic nerve head photography, and optical coherence tomography. The mean RNFL was significantly thinner in glaucomatous eyes than in normal eyes: 95+/-26.3 and 132+/-24.5 microm, respectively. More specifically, the RNFL was significantly thinner in glaucomatous eyes than in normal eyes in the inferior quadrant: 87+/-23.5 and 122+/-24.2 microm, respectively. The mean and inferior quadrant RFNL thicknesses as measured by the optical coherence tomograph showed a statistically significant correlation with glaucoma. Optical coherence tomography may contribute to tracking of juvenile glaucoma progression.

Comparison of macular and peripapillary measurements for the detection of glaucoma

OBJECTIVE

To evaluate macular nerve fiber layer (NFL) thickness in glaucomatous damage by optical coherence tomography (OCT) and to compare its discriminating power for glaucoma and glaucoma suspects with that of total macular thickness and peripapillary NFL thickness.

DESIGN

Cross-sectional, case-control, comparative study.

PARTICIPANTS

A total of 133 eyes from 133 subjects including 46 normal eyes, 48 glaucoma-suspect eyes, and 39 glaucoma eyes were enrolled.

METHODS

Macular NFL thickness, total macular thickness, and peripapillary NFL thickness were measured by Stratus OCT in each diagnostic group.

MAIN OUTCOME MEASURES

The patterns and measurements of macular NFL, total macular, and peripapillary NFL thickness in total mean, 4 quadrants, and 12 clock hours. The discriminating power of each parameter for detection of glaucoma suspects and glaucoma was evaluated by areas under the receiver operating characteristic curve (AROC). Correspondence with visual field function was studied by linear regression analysis.

RESULTS

The macular NFL profile exhibited a double-hump pattern with peaks over superonasal and inferonasal sectors. A significant difference in macular NFL thickness between normal and glaucoma-suspect groups was found at the 6-o'clock position, whereas a difference was found in all except the temporal clock hours between normal and glaucoma subjects. No significant difference in AROCs for detection of glaucoma suspects or glaucoma was found when macular NFL thickness and total macular thickness measurements were compared. However, mean macular NFL thickness demonstrated a stronger correlation with visual function than mean macular thickness (r = 0.39/R2 = 0.15 vs. r = 0.23/R2 = 0.05, P =0.042). Among all the findings, inferior peripapillary NFL thickness had the best performance in discriminating glaucoma (AROC, 0.91) and glaucoma suspects (AROC, 0.67). It also had the strongest correlation with visual function (r = 0.60/R2 = 0.36, P<0.001).

CONCLUSIONS

Macular NFL thickness was significantly reduced in glaucoma. It had a similar discriminating power for glaucoma detection but a stronger correlation with visual function than total macular thickness. Peripapillary NFL thickness, however, outperformed both total macular and macular NFL thickness in terms of glaucoma detection and visual function correlation. Peripapillary NFL thickness, as a total measurement of both macular and peripheral NFL, is still the best surrogate marker in glaucoma assessment.

Macular and retinal nerve fiber layer analysis of normal and glaucomatous eyes in children using optical coherence tomography

PURPOSE

To evaluate macular and nerve fiber layer (NFL) thickness in normal and glaucomatous eyes of children 3 to 17 years old using optical coherence tomography (OCT-3).

DESIGN

Observational cross-sectional study.

METHODS

One hundred fifty-six eyes of 79 patients were enrolled in this institutional study. Fifty-two eyes (33.3%) met criteria for glaucoma and 104 (66.7%) were normal. There were 44 female (55.6%) and 35 male (44.3%) subjects whose ages ranged from 3 to 17 years old (mean 9.5 years, standard deviation 3.5 years, median 9 years). The OCT-3 (Carl Zeiss Meditec, Dublin, California) was used to obtain a fast macular thickness map as well as a fast retinal NFL map of each eye. Data from specific locations around the macula, as well as total macular volume, was analyzed. Similarly, the retinal NFL scan reports average NFL thickness from specific locations around the optic nerve. Data from the superior temporal and inferior temporal sections was analyzed.

RESULTS

There was a statistically significant difference in macular thickness and NFL thickness when normal eyes were compared against those with glaucoma, in all quadrants studied (all P values <or=.001). Mean macular volume was 7.01 +/- 0.42 mm(3) vs 6.57 +/- 0.85 mm(3) for normal vs glaucomatous eyes, respectively (P < .001).

CONCLUSIONS

OCT may prove valuable in the early diagnosis of glaucoma. We have found a difference between normal and glaucomatous eyes in children, similar to that reported in adult studies. Further investigation of OCT testing in children should be considered.

Quantitative assessment of atypical birefringence images using scanning laser polarimetry with variable corneal compensation

PURPOSE

To define the clinical characteristics of atypical birefringence images and to describe a quantitative method for their identification.

DESIGN

Prospective, comparative, clinical observational study.

METHODS

Normal and glaucomatous eyes underwent complete examination, standard automated perimetry, scanning laser polarimetry with variable corneal compensation (GDx-VCC), and optical coherence tomography (OCT) of the macula, peripapillary retinal nerve fiber layer (RNFL), and optic disk. Eyes were classified into two groups: normal birefringence pattern (NBP) and atypical birefringence pattern (ABP). Clinical, functional, and structural characteristics were assessed separately. A multiple logistic regression model was used to predict eyes with ABP on the basis of a quantitative scan score generated by a support vector machine (SVM) with GDx-VCC.

RESULTS

Sixty-five eyes of 65 patients were enrolled. ABP images were observed in 5 of 20 (25%) normal eyes and 23 of 45 (51%) glaucomatous eyes. Compared with eyes with NBP, glaucomatous eyes with ABP demonstrated significantly lower SVM scores (P < .0001, < 0.0001, 0.008, 0.03, and 0.03, respectively) and greater temporal, mean, inferior, and nasal RNFL thickness using GDx-VCC; and a weaker correlation with OCT generated RNFL thickness (R(2) = .75 vs .27). ABP images were significantly correlated with older age (R(2) = .16, P = .001). The SVM score was the only significant (P < .0001) predictor of ABP images and provided high discriminating power between eyes with NBP and ABP (area under the receiver operator characteristic curve = 0.98).

CONCLUSIONS

ABP images exist in a subset of normal and glaucomatous eyes, are associated with older patient age, and produce an artifactual increase in RNFL thickness using GDx-VCC. The SVM score is highly predictive of ABP images.

Objective analysis of retinal damage in HIV-positive patients in the HAART era using OCT

PURPOSE

To assess retinal nerve fiber layer (RNFL) thickness in patients with human immunodeficiency virus (HIV) disease without cytomegalovirus retinitis (CMV).

DESIGN

A case-control study.

METHODS

The study included 113 eyes of 65 patients in one center. Thickness of RNFL along a 3.4-mm-diameter circle centered on the optic nerve head was evaluated using third-generation optical coherence tomography. Patients in group A (39 eyes of 22 patients) were human immunodeficiency virus-negative control subjects. Group B (36 eyes of 18 patients) was composed of HIV patients with no history of CMV retinitis and CD4 counts consistently above 100. Group C (38 eyes of 25 patients) comprised HIV patients with no history of CMV retinitis but a history of CD4 count less than 100 at some point lasting for at least 6 months.

RESULTS

The average RNFL thicknesses in groups A, B, and C were 103.33 +/- 8.50 microm, 103.30 +/- 9.28 microm, and 90.10 +/- 12.50 microm, respectively. Group C had significantly thinner overall RNFL than either of the groups A and B (Tukey-Kramer). This difference was most prominent in temporal, superior, and inferior retinal areas. No difference was in nasal retinal area, nor between groups A and B in any of the areas.

CONCLUSIONS

Significant RNFL thinning occurs in HIV patients without CMV retinitis and with low CD4 counts compared with the same subgroup of patients with CD4 count increased to above 100 and HIV-negative control subjects. Third-generation OCT may be useful in diagnosis of early subclinical HIV-associated visual functional loss.

Evaluation of retinal nerve fiber layer, optic nerve head, and macular thickness measurements for glaucoma detection using optical coherence tomography

PURPOSE

To compare the ability of optical coherence tomography retinal nerve fiber layer (RNFL), optic nerve head, and macular thickness parameters to differentiate between healthy eyes and eyes with glaucomatous visual field loss.

DESIGN

Observational case-control study.

METHODS

Eighty-eight patients with glaucoma and 78 healthy subjects were included. All patients underwent ONH, RNFL thickness, and macular thickness scans with Stratus OCT during the same visit. ROC curves and sensitivities at fixed specificities were calculated for each parameter. A discriminant analysis was performed to develop a linear discriminant function designed to identify and combine the best parameters. This LDF was subsequently tested on an independent sample consisting of 63 eyes of 63 subjects (27 glaucomatous and 36 healthy individuals) from a different geographic area.

RESULTS

No statistically significant difference was found between the areas under the ROC curves (AUC) for the RNFL thickness parameter with the largest AUC (inferior thickness, AUC = 0.91) and the ONH parameter with largest AUC (cup/disk area ratio, AUC = 0.88) (P = .28). The RNFL parameter inferior thickness had a significantly larger AUC than the macular thickness parameter with largest AUC (inferior outer macular thickness, AUC = 0.81) (P = .004). A combination of selected RNFL and ONH parameters resulted in the best classification function for glaucoma detection with an AUC of 0.97 when applied to the independent sample.

CONCLUSIONS

RNFL and ONH measurements had the best discriminating performance among the several Stratus OCT parameters. A combination of ONH and RNFL parameters improved the diagnostic accuracy for glaucoma detection using this instrument.

Comparison of three optical coherence tomography scanning areas for detection of glaucomatous damage

PURPOSE

Several cross-sectional studies have demonstrated the capability of optical coherence tomography (OCT) to detect glaucomatous changes. OCT enables posterior pole scanning of three regions: macula, peripapillary, and optic nerve head (ONH). This study compared the ability of each region to detect glaucomatous damage.

DESIGN

Retrospective observational cross-sectional study.

METHODS

The study included 37 normal (37 subjects) and 37 glaucomatous eyes (26 subjects) that had comprehensive ocular examination, reliable and reproducible Swedish interactive thresholding algorithm standard 24-2 perimetry, and Stratus OCT scanning of macula, peripapillary, and ONH regions on the same visit. Optical nerve head (ONH) appearance did not form part of the inclusion criteria. The main outcome measure, was area under receiver operating characteristic curves (AROCs) that was calculated for each scanning region for distinguishing between normal and glaucomatous eyes.

RESULTS

The highest AROCs for distinguishing between groups were for ONH parameters (rim area = 0.97, horizontal integrated rim width = 0.96, vertical integrated rim area = 0.95) and peripapillary nerve fiber layer (NFL) thickness (0.94) followed by macular volume and thickness (both 0.80). A statistically significant difference existed in ONH and NFL AROCs when compared with macular AROCs (P < or = .007, for both)

CONCLUSIONS

OCT ONH and NFL parameters provided similar discrimination capabilities between healthy eyes and those of glaucoma patients and superior discrimination capabilities when compared with macular parameters.

Optic Nerve Head Topographic Measurements and Retinal Nerve Fiber Layer Thickness in Physiologic Large Cups

PURPOSE

To evaluate the parameters of optic nerve head (ONH) and retinal nerve fiber layer (RNFL) in patients with large cup/disc ratio (CDR) and normal neuroretinal rim configuration who have normal perimetry (physiologic large cups, LC) and to compare these parameters with those of the normal and early glaucoma patients.

METHODS

Using Heidelberg retinal tomography (HRT) and optical coherence tomography (OCT), 30 patients with LC, 29 normal subjects, and 31 early glaucoma patients were examined. One eye from each subject was randomly selected.

RESULTS

Significant differences between LC and glaucomatous eyes (GE) were found in parameters indicating loss of nerve fibers, such as rim area, rim volume, and mean RNFL thickness. However, there was no difference between LC and normal eyes (NE) in RNFL thickness, rim area, and rim volume. LC was able to be defined as a normal central excavation with a large disc and large CDR with a normal rim area.

CONCLUSIONS

HRT ONH parameters and RNFL thickness obtained with OCT may be useful for differentiating between glaucoma and LC eyes.

Evaluation of Scanning Resolution on Retinal Nerve Fiber Layer Measurement Using Optical Coherence Tomography in Normal and Glaucomatous Eyes

PURPOSE

To evaluate the effect of varying the scanning resolution of optical coherence tomography (OCT) retinal nerve fiber layer (RNFL) measurement on diagnostic sensitivity and functional correlation in glaucoma.

PATIENTS AND METHODS

314 eyes from 182 subjects including 107 normal eyes, 83 glaucoma suspect eyes, and 124 glaucoma eyes were included in this cross-sectional study. Standard automated perimetry and OCT measurement of RNFL thickness were performed. Each individual underwent two scanning protocols: (1) fast RNFL thickness (3.4) scan (with resolution of 256 scan points) and (2) RNFL thickness (3.4) scan (with resolution of 512 scan points). RNFL thickness was compared among the groups. Diagnostic sensitivity was evaluated with Receiver Operating Characteristic (ROC) Curve. Relationship between RNFL thickness and visual field mean deviation was examined using linear regression analysis.

RESULTS

Measured RNFL thickness using fast RNFL thickness (3.4) scan was significantly higher compared with RNFL thickness (3.4) scan in average, superior, nasal and inferior RNFL in all diagnostic groups. Comparing normal and glaucoma groups, RNFL thickness (3.4) scan produced the largest area under the ROC curve (0.912) based on average RNFL thickness. A stronger correlation between average RNFL and visual field mean deviation was found in RNFL thickness (3.4) scan (R = 0.75, R = 0.56).

CONCLUSIONS

Higher resolution RNFL scan provides better diagnostic sensitivity in glaucoma detection and a stronger correlation with visual function.

Optical coherence tomography can measure axonal loss in patients with ethambutol-induced optic neuropathy

PURPOSE

To map and identify the pattern, in vivo, of axonal degeneration in ethambutol-induced optic neuropathy using optical coherence tomography (OCT). Ethambutol is an antimycobacterial agent often used to treat tuberculosis. A serious complication of ethambutol is an optic neuropathy that impairs visual acuity, contrast sensitivity, and color vision. However, early on, when the toxic optic neuropathy is mild and partly reversible, the funduscopic findings are often subtle and easy to miss.

METHODS

Three subjects with a history of ethambutol (EMB)-induced optic neuropathy of short-, intermediate-, and long-term visual deficits were administered a full neuro-ophthalmologic examination including visual acuity, color vision, contrast sensitivity, and fundus examination. In addition, OCT (OCT 3000, Humphrey-Zeiss, Dublin, CA) was performed on both eyes of each subject using the retinal nerve fiber layer (RNFL) analysis protocol. OCT interpolates data from 100 points around the optic nerve to effectively map out the RNFL.

RESULTS

The results were compared to the calculated average RNFL of normal eyes accumulated from four prior studies using OCT, n=661. In all subjects with history of EMB-induced optic neuropathy, there was a mean loss of 72% nerve fiber layer thickness in the temporal quadrant (patient A, with eventual recovery of visual acuity and fields, 58% loss; patient B, with intermediate visual deficits, 68% loss; patient C, with chronic visual deficits, 90% loss), with an average mean optic nerve thickness of 26+/-16 microm. There was a combined mean loss of 46% of fibers from the superior, inferior, and nasal quadrants in the (six) eyes of all three subjects (mean average thickness of 55+/-29 microm). In both sets (four) of eyes of the subjects with persistent visual deficits (patients B and C), there was an average loss of 79% of nerve fiber thickness in the temporal quadrant.

CONCLUSIONS

The OCT results in these patients with EMB-induced optic neuropathy show considerable loss especially of the temporal fibers. This is consistent with prior histopathological studies that show predominant loss of parvo-cellular axons (or small-caliber axons) within the papillo-macular bundle in toxic or hereditary optic neuropathies. OCT can be a valuable tool in the quantitative analysis of optic neuropathies. Additionally, in terms of management of EMB-induced optic neuropathy, it is important to properly manage ethambutol dosing in patients with renal impairment and to achieve proper transition to a maintenance dose once an appropriate loading dose has been reached.

Image analysis of optic nerve disease

Existing methodologies for imaging the optic nerve head surface topography and measuring the retinal nerve fibre layer thickness include confocal scanning laser ophthalmoscopy (Heidelberg retinal tomograph), optical coherence tomography, and scanning laser polarimetry. For cross-sectional screening of patient populations, all three approaches have achieved sensitivities and specificities within the 60-80th percentile in various studies, with occasional specificities greater than 90% in select populations. Nevertheless, these methods are not likely to provide useful assistance for the experienced examiner at their present level of performance. For longitudinal change detection in individual patients, strategies for clinically specific change detection have been rigorously evaluated for confocal scanning laser tomography only. While these initial studies are encouraging, applying these algorithms in larger numbers of patients is now necessary. Future directions for these technologies are likely to include ultra-high resolution optical coherence tomography, the use of neural network/machine learning classifiers to improve clinical decision-making, and the ability to evaluate the susceptibility of individual optic nerve heads to potential damage from a given level of intraocular pressure or systemic blood pressure.

Delayed absorption of macular edema accompanying serous retinal detachment after grid laser treatment in patients with branch retinal vein occlusion☆

PURPOSE

To study the detailed process of macular edema (ME) absorption after grid laser photocoagulation in patients with branch retinal vein occlusion (BRVO). The influence of pretreatment serous retinal detachment (SRD) at the fovea on patient outcome was also evaluated.

DESIGN

Retrospective, interventional, comparative case series.

PARTICIPANTS

Thirty-seven BRVO patients presenting with severe ME.

METHODS

Patients were treated with grid laser photocoagulation with 6 months of follow-up examinations. Baseline and post-treatment examinations included measurements of visual acuity (VA), fluorescein angiography, and detailed imaging of ME by optical coherence tomography (OCT). Macular thickness was defined as the distance from the inner retinal surface to the outer border of the sensory retina (foveal retinal thickness) and also to the inner border of the retinal pigment epithelium including the SRD (total foveal elevation).

MAIN OUTCOME MEASURES

Post-treatment macular thickness with OCT, VA converted to the logarithm of the minimum angle of resolution, and absorption of SRD, and correlations of macular thickness and VA both before and after treatment.

RESULTS

Total foveal elevation and VA were significantly improved at 1, 3, and 6 months after treatment. There was also a significant correlation between reduction of total foveal elevation and increase in VA. Fourteen eyes (37.8%) displayed SRD, as evidenced by OCT at the baseline. In eyes without SRD, foveal retinal thickness and VA had significantly improved in a time-dependent manner. However, although SRD itself was almost absorbed 6 months after treatment, the improvement of both VA and total foveal elevation in eyes with pretreatment SRD was not significant compared with baseline conditions. Both post-treatment total foveal elevation and VA of eyes with SRD tended to be worse than eyes without SRD.

CONCLUSION

The presence of subfoveal SRD retards the absorption of ME and recovery of VA after grid laser photocoagulation in patients with BRVO.