Quantitative mapping of the retinal thickness at the posterior pole in chronic open angle glaucoma

Automated Detection of Hemifield Difference across Horizontal Raphe on Ganglion Cell--Inner Plexiform Layer Thickness Map

PURPOSE

A MATLAB-based (The MathWorks, Inc, Natick, MA) computer program (the ganglion cell-inner plexiform layer [GCIPL] hemifield test) for automated detection of GCIPL thickness difference across the horizontal raphe was developed, and its glaucoma diagnostic performance was assessed.

DESIGN

Cross-sectional study.

PARTICIPANTS

A total of 65 eyes of normal, healthy subjects along with 162 eyes of patients with glaucoma (79 preperimetric and 83 early perimetric).

METHODS

Cirrus high-definition optical coherence tomography (HD-OCT) (Carl Zeiss Meditec, Dublin, CA) was used to scan all of the subjects' macular and optic discs. A positive (i.e., "outside normal limits") GCIPL hemifield test result was declared if the following 3 conditions were all met: (1) The reference line (a horizontal line dividing the superior and inferior hemifields) is continuously detected for longer than one-half of the distance from the temporal inner elliptical annulus to the outer elliptical annulus; (2) the average GCIPL thickness difference within 10 pixels of the reference line, both above and below, is ≥5 μm; and (3) the average RGB color ranges of the 10 pixels above and below the reference line display blue in 1 hemifield and red/yellow/white in the other hemifield.

MAIN OUTCOME MEASURES

Comparison of diagnostic ability using the areas under the receiver operating characteristic curves (AUCs).

RESULTS

A positive GCIPL hemifield test result was observed more frequently in the glaucomatous eyes (74/79 preperimetric, 78/83 early perimetric) than in the normal eyes (1/65). In the preperimetric group, the AUC of the GCIPL hemifield test (0.967; sensitivity 94.94%, specificity 98.46%) was greater than that of the minimum GCIPL thickness (0.933), the inferotemporal GCIPL thickness (0.907), and the average GCIPL thickness (0.899) (P=0.09, 0.06, and 0.03, respectively). In the early perimetric group, the AUC of the GCIPL hemifield test (0.962; sensitivity 93.98%, specificity 96.46%) was greater than that of the inferotemporal GCIPL thickness (0.938), the minimum GCIPL thickness (0.919), and the average GCIPL thickness (0.912) (P=0.38, 0.17, and 0.11, respectively).

CONCLUSIONS

For discrimination of early glaucomatous structural loss, most notably in preperimetric glaucoma cases, identification of the GCIPL thickness difference across the horizontal raphe was effective.

Use of macular thickness parameters for the diagnosis of primary open-angle glaucoma

INTRODUCTION

Retinal thickness in primary open-angle glaucoma patients was determined to establish its correlation with advancement of glaucoma neuropathy.

MATERIAL AND METHODS

One hundred ninety-four patients (371 eyes, age 30-65 years) were divided in 3 groups including 50 patients with confirmed primary open-angle glaucoma, 67 primary open-angle glaucoma-suspected patients and 77 healthy persons (control group). The retinal foveola, foveal, peri-foveal and posterior pole average thickness values were determined with an RTA analyzer. For comparison, linear cup-to-disc diameter ratio (C/D), nerve fiber index (NFI) and mean defect of the retina sensitivity (MD) were also determined.

RESULTS

Statistically highly significant differences in the retinal thickness and glaucoma parameters between the individual groups were observed. In the peri-foveal region, the retinal thickness in glaucoma patients was only 173.0 ±11.4 µm while in the healthy patients 201.1 ±13.1 µm. In the posterior pole region, the thickness values were only 168.1 ±11.3 µm and 195.7 ±12.3 µm, respectively. A moderate correlation between retinal thickness in peri-foveal and posterior pole regions and the C/D, NFI and MD parameters was also established (Pearson coefficients below -0.351 or above 0.284).

CONCLUSIONS

The retinal thickness in the peri-foveal and posterior pole regions depends on the degree of glaucoma advancement. This original observation may be a basis for acceptance of this method as a quite new tool in glaucoma diagnosis.

Glaucoma diagnostic accuracy of ganglion cell-inner plexiform layer thickness: comparison with nerve fiber layer and optic nerve head

PURPOSE

To determine the diagnostic performance of macular ganglion cell-inner plexiform layer (GCIPL) thickness measured with the Cirrus high-definition optical coherence tomography (HD-OCT) ganglion cell analysis (GCA) algorithm (Carl Zeiss Meditec, Dublin, CA) to discriminate normal eyes and eyes with early glaucoma and to compare it with that of peripapillary retinal nerve fiber layer (RNFL) thickness and optic nerve head (ONH) measurements.

DESIGN

Evaluation of diagnostic test or technology.

PARTICIPANTS

Fifty-eight patients with early glaucoma and 99 age-matched normal subjects.

METHODS

Macular GCIPL and peripapillary RNFL thicknesses and ONH parameters were measured in each participant, and their diagnostic abilities were compared.

MAIN OUTCOME MEASURES

Area under the curve (AUC) of the receiver operating characteristic.

RESULTS

The GCIPL parameters with the best AUCs were the minimum (0.959), inferotemporal (0.956), average (0.935), superotemporal (0.919), and inferior sector (0.918). There were no significant differences between these AUCs and those of inferior quadrant (0.939), average (0.936), and superior quadrant RNFL (0.933); vertical cup-to-disc diameter ratio (0.962); cup-to-disc area ratio (0.933); and rim area (0.910), all P>0.05.

CONCLUSIONS

The ability of macular GCIPL parameters to discriminate normal eyes and eyes with early glaucoma is high and comparable to that of the best peripapillary RNFL and ONH parameters.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found after the references.

Posterior pole retinal thickness measurements by the retinal thickness analyzer in healthy Chinese subjects

PURPOSE

To assess retinal thickness at the posterior pole in healthy Chinese subjects with the retinal thickness analyzer (RTA).

METHODS

Retinal thicknesses at the posterior pole and fovea were measured by the RTA in 331 eyes of 178 healthy Chinese subjects. Retinal thicknesses as a function of sex, age, refractive errors, and axial length were also evaluated.

RESULTS

The average thickness of the foveal area +/- SD was 158.6 +/- 24.8 microm, the average thickness of the perifoveal region (600-2,500 microm from fovea) +/- SD was 174 +/- 25.2 microm, and the average thickness of the posterior pole region (600-6,000 microm from fovea) +/- SD was 171.9 +/- 25.3 microm. There was no significant difference in retinal thicknesses of the foveal, perifoveal, and posterior pole regions in either right or left eyes or as a function of different spherical equivalents. Moreover, there was no significant difference of foveal thickness between males and females. Greater retinal thicknesses of the foveal, perifoveal, and posterior pole regions were associated with age of older than 40 years and axial length of < 24 mm, and greater perifoveal and posterior pole thicknesses were found for females. Furthermore, there were no significant correlations between age, refractive errors, and axial lengths with retinal thicknesses.

CONCLUSION

Retinal thicknesses of the posterior pole region differed by age, axial length, and sex, but there was no effect of laterality or different spherical equivalents. The RTA is a fast and noninvasive technology to assess retinal conditions with thickening or thinning in the fovea and posterior pole.

Diagnostic accuracy of the Retinal Thickness Analyser: differentiation between normal eyes and eyes with glaucoma or macular pathologies

BACKGROUND

The Retinal Thickness Analyser (RTA) is intended to detect glaucomatous changes as well as macular pathologies at the posterior pole. We determined the diagnostic accuracy for eyes with manifest glaucoma or macular diseases.

METHODS

We examined 71 eyes with long-term, established eye conditions. Included were 28 eyes with glaucoma, 21 with different macular diseases and 22 normal eyes. All examinations were evaluated in a blind-test by RTA experts without any clinical information on the patients. After comparison of the RTA interpretation with the clinical diagnosis, we determined sensitivity, specificity, positive and negative predictive values.

RESULTS

Of 71 examinations, 15 (21%) were not interpretable. If these results are excluded, the following diagnostic accuracy values were calculated for glaucoma and macular disorders respectively: sensitivity 75 and 59%, specificity 55 and 97%, positive predictive value 48 and 90% and negative predictive value 80 and 84%. These values were not significantly different when both eyes of each patient were included in the final analysis (n=133).

CONCLUSION

The diagnostic values of the RTA determined in this case control study were not satisfactory. However, no clinical information was used in the assessment. The extent to which additional clinical information increases the diagnostic value remains to be determined.

Advances in glaucoma therapeutics

Glaucoma is a major cause of irreversible blindness in the world. The prevalence of glaucomatous loss in vision will continue to grow as our populations age. Ocular hypertension is a major risk factor for the development of glaucoma and current glaucoma therapy is directed at lowering intraocular pressure. Several new ocular hypotensive agents have been introduced in the past several years providing a variety of treatment options. In addition, various classes of neuroprotective agents demonstrating activity in a wide variety of animal models have been proposed as potential new glaucoma therapeutics. Although these approaches will slow the progression of vision loss, they do not directly intervene in the disease process(es). Advances have been made attempting to understand the pathogenic pathways involved in glaucomatous damage to the eye and in methods to clinically measure glaucoma damage. An increased understanding of the pathophysiology of glaucoma will lead to the development of new therapeutic agents that intervene and perhaps even reverse glaucomatous damage to the eye. There also is a need to develop new methods to clinically measure glaucoma damage because, currently, considerable damage occurs before glaucoma is diagnosed and glaucoma remains underdiagnosed in the general population.

Retinal thickness at the posterior pole in glaucoma and ocular hypertension

PURPOSE

Ganglion cells with nerve fibre layer contribute a substantial fraction to the retinal thickness (RT). In contrast to the analysis of papillary and peripapillary area, which have shown large variability in normal eyes, the variation of retinal cell density in the perifoveal region is reported to be less than 10%. By measuring RT at the posterior pole we wanted to detect retinal changes due to glaucoma and determine their correspondence with visual field (VF) changes.

METHODS

The Retinal Thickness Analyzer (RTA) was used to obtain RT maps in 21 normal eyes, 20 eyes with ocular hypertension and 22 eyes with glaucoma. A green laser slit (540 nm) of the RTA was focused on the retina at an angle and its intersection with the retina was imaged. The distance between the reflections from the vitreo-retinal and retina-retinal pigment interface is directly proportional to the RT. Five locations covering the central 20 degrees were scanned, generating 10 optical cross sections that were transformed into colour-coded RTA maps. Numerical data were presented for the perifoveal and posterior pole region.

RESULTS

In glaucomatous eyes significant localised thinning of the retina was present, identified as the increased number of clusters including at least four points that are 2 standard deviations below normal. The minimum retinal thickness was decreased in glaucoma eyes and the perifoveal temporal modulation and perifoveal temporal/nasal asymmetry--indicators of greater RT loss in the temporal and the nasal quadrant, respectively--were higher in eyes with glaucoma, but with overlapping global indices between the groups. In 16 of 22 eyes with glaucoma there was good agreement of RT changes with VF defects. In two eyes with typical glaucomatous damage at the optic disc but without VF defects localised changes of RT were detected.

CONCLUSIONS

The RTA enables objective noninvasive evaluation of the posterior pole and could become helpful in diagnosis of glaucoma before the onset of functional damage. However, at present its clinical usefulness is limited by overlapping values of retinal thickness between normal and glaucomatous populations.

Eccentricity and measurement variability and repeatability with the retinal thickness analyser

AIMS

To define the variability and repeatability of retinal thickness measurements using the retinal thickness analyser (RTA) and to elucidate any interaction between eccentricity (that is, position relative to the fovea) and variability and repeatability.

METHODS

The sample comprised 20 normal subjects of mean age 33 years. Each subject attended for two visits. Repeated RTA scans were acquired centred on the fovea and for any one of the four possible non-foveal scan areas. The mean retinal thickness (+SD) was calculated for a series of concentric circular bands centred on fixation. A repeated measures analysis of variance (ANOVA) was used to determine any significant interaction between the variability of RTA thickness values and eccentricity.

RESULTS

The group mean coefficient of variation and coefficient of repeatability were highest at the fovea. The repeated measures ANOVA revealed that the within test variability of RTA measurements varied significantly with eccentricity (p<0.0001). Similarly, the between test repeatability varied significantly with eccentricity (p = 0.045).

CONCLUSION

The significantly elevated within test variability and between test repeatability in the foveal area need to be considered when using the RTA to evaluate patients with macular disease.