Analysis of Macular Thickness in British Population Using Optical Coherence Tomography (OCT): An Emphasis on Interocular Symmetry

When Sex Matters: Differences in the Central Nervous System as Imaged by OCT through the Retina

BACKGROUND

Retinal texture has gained momentum as a source of biomarkers of neurodegeneration, as it is sensitive to subtle differences in the central nervous system from texture analysis of the neuroretina. Sex differences in the retina structure, as detected by layer thickness measurements from optical coherence tomography (OCT) data, have been discussed in the literature. However, the effect of sex on retinal interocular differences in healthy adults has been overlooked and remains largely unreported.

METHODS

We computed mean value fundus images for the neuroretina layers as imaged by OCT of healthy individuals. Texture metrics were obtained from these images to assess whether women and men have the same retina texture characteristics in both eyes. Texture features were tested for group mean differences between the right and left eye.

RESULTS

Corrected texture differences exist only in the female group.

CONCLUSIONS

This work illustrates that the differences between the right and left eyes manifest differently in females and males. This further supports the need for tight control and minute analysis in studies where interocular asymmetry may be used as a disease biomarker, and the potential of texture analysis applied to OCT imaging to spot differences in the retina.

Warwick A, Müller PL, Williams KM, Rudnicka AR, Owen CG, Lee AY, Egan C, Tufail A. Foveal Curvature and Its Associations in UK Biobank Participants

Purpose

To examine whether sociodemographic, and ocular factors relate to optical coherence tomography (OCT)-derived foveal curvature (FC) in healthy individuals.

Methods

We developed a deep learning model to quantify OCT-derived FC from 63,939 participants (age range, 39-70 years). Associations of FC with sociodemographic, and ocular factors were obtained using multilevel regression analysis (to allow for right and left eyes) adjusting for age, sex, ethnicity, height (model 1), visual acuity, spherical equivalent, corneal astigmatism, center point retinal thickness (CPRT), intraocular pressure (model 2), deprivation (Townsend index), higher education, annual income, and birth order (model 3). Fovea curvature was modeled as a z-score.

Results

Males had on average steeper FC (0.077; 95% confidence interval [CI] 0.077-0.078) than females (0.068; 95% CI 0.068-0.069). Compared with whites, non-white individuals showed flatter FC, particularly those of black ethnicity. In black males, -0.80 standard deviation (SD) change when compared with whites (95% CI -0.89, -0.71; P 5.2e10-68). In black females, -0.70 SD change when compared with whites (95% CI -0.77, -0.63; p 2.3e10-93). Ocular factors (visual acuity, refractive status, and CPRT) showed a graded inverse association with FC that persisted after adjustment. Macular curvature showed a positive association with FC. Income showed a linear trend increase in males (P for linear trend = 0.005).

Conclusions

We demonstrate marked differences in FC with ethnicity on the largest cohort studied for this purpose to date. Ocular factors showed a graded association with FC. Implementation of FC quantification in research and on the clinical setting can enhance the understanding of clinical macular phenotypes in health and disease.

Determinants of vitreomacular traction width: associations with foveal floor width and vitreoretinal interface changes

To investigate the relationship between vitreomacular traction (VMT) width, foveal floor width (FFW) and other anatomical characteristics between eyes of patients with VMT. Retrospective observational study of unilateral and bilateral VMT cases from two specialist ophthalmic centres in the United Kingdom (UK) between 2016 and 2018. For unilateral VMT cases: VMT width in the affected eye and FFW in the non-affected fellow eye were measured. In bilateral VMT cases: VMT width in both eyes was measured. In all cases, the presence of any associated inner or outer retinal, and vitreoretinal interface (VRI) changes, including epiretinal membrane, was also documented. 88 patients fulfilled the study criteria: 57 having unilateral and 31 bilateral VMT. For unilateral VMT cases, log (VMT) width was significantly correlated with FFW (r = 0.347, p = 0.008). Using stepwise linear regression, FFW (p = 0.004) and VRI changes (p = 0.03) were both significantly associated with VMT width with a R² of 0.21. In bilateral VMT cases, there was strong positive correlation between log (VMT) width (r = 0.88, p < 0.001), and the presence of any VRI (r = 0.90, p < 0.001) or outer retinal changes (r = 0.50, p < 0.001) between the two eyes. These findings suggest that individual variations in foveal morphology as measured by the FFW, along with the presence of vitreoretinal interface changes, are associated with the extent of VMT width. VMT width, VRI and outer retinal changes were also highly correlated between eyes in bilateral VMT, suggesting that individual patient factors, which may be genetic or acquired, determine their presence and extent.

Optical coherence tomography (OCT) in neuro-ophthalmology

Optical coherence tomography (OCT) is a non-invasive medical imaging technology that is playing an increasing role in the routine assessment and management of patients with neuro-ophthalmic conditions. Its ability to characterise the optic nerve head, peripapillary retinal nerve fibre layer and cellular layers of the macula including the ganglion cell layer enables qualitative and quantitative assessment of optic nerve disease. In this review, we discuss technical features of OCT and OCT-based imaging techniques in the neuro-ophthalmic context, potential pitfalls to be aware of, and specific applications in more common neuro-ophthalmic conditions including demyelinating, inflammatory, ischaemic and compressive optic neuropathies, optic disc drusen and raised intracranial pressure. We also review emerging applications of OCT angiography within neuro-ophthalmology.

The Association between Foveal Floor Measurements and Macular Hole Size

PURPOSE

Determining which factors influence idiopathic macular hole (MH) size is important because it is a major prognostic indicator of treatment success. Foveal pit morphologic features are highly symmetrical within individuals and may influence idiopathic MH size. Using a series of patients with unilateral idiopathic MHs, we examined the foveal floor size of the fellow eye to evaluate its relationship with idiopathic MH size and postoperative outcomes.

DESIGN

Retrospective observational study.

PARTICIPANTS

Two hundred forty-one participants with a unilateral idiopathic MH treated with surgery and a fellow eye with no ocular pathologic features.

METHODS

Both eyes underwent spectral-domain (SD) OCT imaging at the time of surgery. Minimum linear diameter (MLD) and base diameter (BD) defined idiopathic MH size. Foveal floor width (FFW) and minimal foveal thickness defined foveal pit morphologic features of the fellow eye.

MAIN OUTCOME MEASURES

Baseline characteristics, SD OCT measurements, and preoperative variables were compared to determine their relationship with idiopathic MH size and postoperative visual acuity (VA) in logarithm of the minimum angle of resolution units.

RESULTS

Foveal floor width was correlated with MLD (r = 0.36; P ≤ 0.001) and BD (r = 0.30; P ≤ 0.001), but not postoperative VA. Minimum linear diameter correlated with preoperative VA (r = 0.49; P ≤ 0.0001) and postoperative VA (r = 0.54; P ≤ 0.0001). A 2-stage regression model was developed to predict postoperative VA (r² = 0.28): preoperative VA (β = 0.36; P = 0.002) explained 13% of variability and MLD (β = 0.29; P = 0.002), and idiopathic MH duration (β = 0.23; P = 0.004) explained a further 16%.

CONCLUSIONS

Foveal floor width of the fellow eye in patients with a unilateral idiopathic MH was correlated significantly with idiopathic MH size and may explain some of the variability in idiopathic MH size observed between individuals. However, FFW could not predict postoperative vision.

Macular thickness measurements of healthy, naïve cynomolgus monkeys assessed with spectral-domain optical coherence tomography (SD-OCT)

The purpose of this study was to measure central macular thickness in an unprecedented number of cynomolgus monkeys. Macular thickness was measured with Heidelberg spectral-domain OCT in 320 eyes of healthy and treatment-naïve cynomolgus monkeys (80 males and 80 females). The macula was successfully measured in all 320 eyes. Macular thickness was not significantly different between the sexes. The mean central macular thickness was 244 μm (+/- 21 μm). Macular thicknesses in the quadrants were 327 +/-17 μm (temporal inner), 339 +/- 17 μm (inferior inner), 341 +/- 14 μm (superior inner), 341 +/-18 μm (nasal inner), and 299 +/- 20 μm (temporal outer), 320 +/- 16 μm (superior outer), 332 +/-23 μm (inferior outer), and 337 +/-18 μm (nasal outer). Highly significant differences between the nasal and temporal quadrants were detected. This study successfully demonstrated the feasibility of retinal thickness measurements in healthy cynomolgus monkeys. The present findings indicate that the macula is thicker in cynomolgus monkeys than in humans and provide important normative data for future studies.

Racial differences and determinants of macular thickness profiles in multiethnic Asian population: the Singapore Epidemiology of Eye Diseases Study

Aim

To evaluate racial differences, and ocular and systemic determinants of macular thickness (MT), measured by spectral-domain optical coherence tomography (SD-OCT) in a normal multiethnic Asian population.

Method

MT was measured from a 6×6 mm2 central macular area using the Cirrus high-definition OCT (HD-OCT) (Carl Zeiss Meditec, Dublin, CA). The associations between ocular and systemic factors with MT were evaluated using linear regression analyses with generalised estimating equation models to account for intereye correlation.

Results

7447 healthy eyes (2577 Chinese, 2072 Malays and 2798 Indians) of 4510 subjects were included. Multivariable analysis showed that older age (per decade, β=−4.39), female gender (β=−5.74), diabetes (β=−1.10), chronic kidney disease (CKD) (β=−3.21), longer axial length (per mm, β=−2.34), flatter corneal curvature (per mm, β=−1.79) and presence of cataract (β=−0.94) were associated with thinner overall average MT (OMT) (all p≤0.026); higher total cholesterol (β=0.44; p=0.010) was associated with thicker OMT. All these factors were also associated with thinner central subfield MT (CSMT) (all p≤0.001), except for cataract, total cholesterol and CKD. Meanwhile, longer axial length (β=2.51; p<0.001) was associated with thicker CSMT. OMT (mean±SD) was thickest in Chinese (279.9±12.5 µm), followed by Malays (276.5±13.7 µm) and Indians (272.4±13.1 µm), with p≤0.003 for all interethnic comparisons. Similar trend was observed for CSMT.

Conclusion

There are interethnic differences in MT profile among Asians, particularly between Chinese and Indians. Ocular and systemic factors affect MT measurements as well. This Asian-specific information may be incorporated into existing clinical interpretation of macular OCT scans to aid in improving the diagnostic and monitoring accuracy of macular diseases among Asians.

Retinal Nerve Fiber Layer Changes Following Primary Retinal Detachment Repair with Silicone Oil Tamponade and Subsequent Oil Removal

Purpose:

To evaluate the correlation between the retinal nerve fiber layer (RNFL), particularly the temporal RNFL (TRNFL), and visual outcomes following surgery for rhegmatogenous retinal detachment (RRD).

Methods:

This retrospective study was performed at a tertiary center; 32 patients underwent single and successful vitrectomy for total RRD using silicone oil as tamponade. Data were collected after oil removal. RNFL thickness and central foveal thickness (CFT) were measured using spectral domain optical coherence tomography. RNFL thickness and CFT of normal eyes were acquired as a control to calculate percentage changes in the affected eyes. The correlation between postoperative best-corrected visual acuity (BCVA) and TRNFL changes was the primary outcome measure.

Results:

Postoperative BCVA correlated negatively with retinal detachment (RD) duration (Pearson coefficient 0.56, P = 0.001) and percentage loss in TRNFL thickness (Pearson Coefficient 0.41, P = 0.02). The macula lost the maximum RNFL thickness (26%). The mean percentage loss of TRNFL was significantly higher in patients with postoperative BCVA <6/60 (42.63% vs. 24.06%, P = 0.009). Patients with postoperative BCVA <6/60 had a significantly longer mean RD duration (29 days) than those with postoperative BCVA >6/60 (17.5 days) (P = 0.026).

Conclusion:

When eyes with RRD are successfully repaired using silicone oil tamponade, the thickness of the RNFL decreases, particularly in the macula, and less macular neuronal loss is associated with better visual outcomes.

Interocular Symmetry of Vascular Density and Association with Central Macular Thickness of Healthy Adults by Optical Coherence Tomography Angiography

In order to analyze the interocular correlation of vascular density, foveal avascular zone (FAZ) size, central macular thickness (CMT), and to investigate the relationship between vascular density and CMT in normal eyes, retinal vascular density in superficial capillary plexus (SCP), deep capillary plexus (DCP) and choriocapillaris (CC) networks, FAZ size, and CMT were visualized by optical coherence tomography (OCT) angiography. A total of 174 eyes of 87 normal Chinese subjects were enrolled in the study. The results showed that FAZ and CMT measurements are not statistically significant between right and left eyes, but right eyes had higher vascular density in superficial, deep retinal capillary and choriocapillaris networks, which might be related with dominant eyes. Spearman correlation test revealed a high correlation between right and left eyes for FAZ and CMT measurements (r = 0.934; r = 0.935), and a moderate correlation for SCP, DCP and CC density (r = 0.402; r = 0.666; r = 0.417). The analysis showed greater vascular density with smaller FAZ size, and a high negative relationship between FAZ and CMT, which indicates a positive correlation between retinal blood supply and retinal thickness.

Lateral thinking - Interocular symmetry and asymmetry in neurovascular patterning, in health and disease

No biological system or structure is likely to be perfectly symmetrical, or have identical right and left forms. This review explores the evidence for eye and visual pathway asymmetry, in health and in disease, and attempts to provide guidance for those studying the structure and function of the visual system, where recognition of symmetry or asymmetry may be essential. The principal question with regards to asymmetry is not 'are the eyes the same?', for some degree of asymmetry is pervasive, but 'when are they importantly different?'. Knowing if right and left eyes are 'importantly different' could have significant consequences for deciding whether right or left eyes are included in an analysis or for examining the association between a phenotype and ocular parameter. The presence of significant asymmetry would also have important implications for the design of normative databases of retinal and optic nerve metrics. In this review, we highlight not only the universal presence of asymmetry, but provide evidence that some elements of the visual system are inherently more asymmetric than others, pointing to the need for improved normative data to explain sources of asymmetry and their impact on determining associations with genetic, environmental or health-related factors and ultimately in clinical practice.

Immediate Postoperative Intraocular Pressure Adjustment Reduces Risk of Cystoid Macular Edema after Uncomplicated Micro Incision Coaxial Phacoemulsification Cataract Surgery

Purpose

To determine the accuracy of visual estimation of immediate postoperative intraocular pressure (IOP) following microincision cataract surgery (MICS) and the effect of immediate postoperative IOP adjustment on prevention of cystoid macular edema (CME).

Setting

Ambulatory surgical center.

Methods

Prospective, randomized analysis of 170 eyes in 135 patients with MICS, performed in a Medicare approved outpatient ambulatory surgery center. Surgical parameters included a keratome incision of 1.5 mm to 2.8 mm, topical anesthetic, case completion IOP estimation by palpation and patient visualization of light, and IOP adjustment before exiting the operating theater. IOPs were classified into three groups: low (<16 mmHg), normal (16 to 21 mmHg), and elevated (>21 to 30 mmHg). IOP measurements were repeated 1 day after surgery. Optical coherence tomography (Stratus OCT, Zeiss) was measured at 2 weeks. An increase in foveal thickness greater than 15 µm was used to indicate CME. Statistical analysis was performed using one- and two-tailed Student's t-tests.

Results

Mean minimal foveal thickness averaged 207.15 µm in the low pressure group, 205.14 µm in the normal IOP group, and 210.48 µm in the elevated IOP group 2 weeks following surgery. CME occurred in 14 of 170 eyes (8.2%) at 2 weeks (low IOP, 35.7%; normal IOP, 14.2%; elevated IOP, 50.0%). Change in IOP from the operating theater to 1 day after surgery was within +/−5 mmHg in 54 eyes (31.7%), elevated by 6 to 15 mmHg in 22 eyes (12.9%), and elevated more than 15 mmHg in four eyes (2.3%). IOP was reduced by 6 mmHg to 15 mmHg in 39 eyes (22.9%) and reduced by more than 15 mmHg in nine eyes (5.3%).

Conclusions

Immediate postoperative adjustment of IOP may prevent CME in MICS. Physicians can improve their ability to estimate postoperative IOP with experience in tonometry to verify immediate postoperative IOP. There are patient safety and economic benefits to immediate IOP adjustment in the operating theater.

Synopsis

Immediate postoperative IOP adjustment following cataract surgery before the patient leaves the operating theater may reduce the incidence of CME and provide patient safety and economic benefits.

Macular thicknesses and their associations with ocular and demographic variables in black South Africans

Purpose: To determine normal macular thicknesses and their associations with demographic and ocular variables in healthy eyes of black South Africans.Methods: Six hundred healthy subjects (N = 600) underwent height and weight measurements followed by a complete ophthalmic examination, which included auto-refraction, subjective refraction, slit-lamp biomicroscopy, ocular biometric measurements and tonometry. Intraocular pressure (IOP) was measured with the Nidek NT530P (Tonopachy™) and the axial length (AL) thickness with the Nidek Echoscan. The central corneal thickness (CCT) and macular thickness were measured using iVue-100 spectral-domain optical coherence tomography (Optovue, Inc.). The macular thickness map protocol that divides the macular area into nine regions of the Early Treatment Diabetic Retinopathy Study (ETDRS) fields was used. Variations in macular thickness measurements with body mass index (BMI), age, gender, refraction, AL, CCT and IOP were determined with partial correlation analysis.Results: The 600 subjects had a mean age of 28.15 ± 13.09 years (range = 10–66 years), with 305 (50.83%) being males and 295 (49.17%) females. The thickness values of the central, inner and outer maculae were normally distributed, with means of 235.89 µm ± 20.04 µm, 303.56 µm ± 18.68 µm and 287.81 µm ± 14.61 µm, respectively. Mean total macular thickness for all subjects was 268.72 ± 15.04 µm. The temporal quadrant was markedly thinner than all other quadrants for both inner and outer macular regions. Macular thicknesses were greater in men than in women (p < 0.05). The thickness of mean central, mean inner and mean outer maculae increased significantly with increasing BMI (p < 0.001). Central, inner and outer maculae were significantly associated (p < 0.001) with a high hyperopic spherical equivalent refraction. AL was associated with a thin inner macula (p < 0.05) and an outer macula (p < 0.001), but not with a thinner central macula (p > 0.05). Age, CCT and IOP were not associated with macular thickness values in any quadrant (p > 0.05).Conclusion: The macular values were thinner in women than in men and were related to BMI, gender, hyperopic spherical refraction and AL with regional variations. These differences should be considered when interpreting optical coherence tomography results for accurately diagnosing and managing retinal abnormalities.

Effects of age and gender on macular thickness in healthy subjects using spectral optical coherence tomography/scanning laser ophthalmoscopy

PURPOSE

To examine healthy subjects for normal macular thickness values and determine the effects of gender and age in a Turkish population, using spectral optical coherence tomography/scanning laser ophthalmoscopy (OCT/SLO).

MATERIAL AND METHOD

Six hundred fourteen eyes of 307 subjects with no history of ocular diseases and normal ophthalmic examination were recruited in this cross-sectional, prospective study. The participants were divided into three groups based on age (between 20 and 29 years: group 1, between 30 and 39 years: group 2, between 40 and 49 years: group 3). All subjects were scanned with spectral OCT/SLO, performed by one examiner to acquire the retinal thickness map in the ETDRS grid, and values were recorded for nine sectors, and effects of age and gender were evaluated.

RESULTS

When all the subjects were evaluated, the thicknesses were lower in women than men in all sectors (p < 0.001). When divided in groups based on age, this difference remained only in the outer segments. However, the differences in outer layers, except outer nasal layer, were thicker in women in group 3 when compared to others in group 3. When compared between groups, only central thickness in group 3 was shown to be higher than group 1 (p = 0.06). There was no significant difference of thicknesses in any sector when compared right and left eyes of all subjects.

CONCLUSIONS

The study reports the variation in retinal thickness between age and gender in a relatively large sample of a Turkish population. It is important to consider these effects while interpreting the OCT images to make an appropriate diagnosis in retinal diseases.

Segmental Analysis of Macular Layers in Patients With Unilateral Primary Open-Angle Glaucoma

PURPOSE

To measure the thicknesses of the inner layers of the macula in both eyes of patients with unilateral primary open-angle glaucoma (POAG) and compare them with normal control eyes.

METHODS

This prospective, cross-sectional pilot study enrolled patients with unilateral POAG, who had visual field defect in only 1 eye, and controls with a normal eye examination. Horizontal and vertical B-scan images centered on the fovea were obtained using spectral domain optical coherence. Semiautomatic delineation and segmentation of the inner layers of the retina were performed to evaluate macular retinal nerve fiber layer (mRNFL), ganglion cell complex (GCC) and ganglion cell-inner plexiform layer (GC-IPL) thicknesses. Mean, superior, inferior, nasal, and temporal inner macular layer thicknesses were compared between affected eyes, fellow eyes without visual field defect, and control eyes.

RESULTS

Nineteen patients with unilateral POAG and 14 normal control eyes were enrolled. In the affected POAG eyes, thinning of the mRNFL, GCC, and GC-IPL layers on horizontal and vertical scans were significant when compared with controls (P<0.05), particularly on vertical scans (P<0.001). The mean regional macular GCC and GC-IPL were most severely thinned in the inferior and temporal perifoveal regions. The unaffected eye of patients with unilateral POAG showed significant thinning of the mRNFL only in the vertical scan when compared with normal controls (P<0.05).

CONCLUSIONS

Spectral domain optical coherence tomography detected significant thinning of the mRNFL, GCC, and GC-IPL in the affected eyes of patients with unilateral POAG. Fellow eyes showed early structural changes only in the vertical mRNFL scans when compared with normal controls.

Macular thickness and volume in the elderly: A systematic review

Ageing leads to a number of changes in the body including the macula. Detailed imaging using optical coherence tomography have enabled in vivo studies of how macula changes with age. Here we systematically review 49 studies (9115 participants and 11,577 eyes) to provide an overview of how ageing manifests in the macula of the elderly focusing on clinical relevant measures that are thicknesses and volumes of different macular areas. Ageing seems to increase center point foveal thickness. Ageing does not seem to change the center subfield thickness significantly. Ageing decreases the inner and outer macular thickness, and the overall macular thickness and volume. Studies find that specific retinal layers at specific locations seem to be the contributor to these changes. These findings confirm that age-related changes suggested in histological studies are measurable in vivo on thickness and volume and differ depending on location. Studies are needed to explore reasons for the large variance in measurements and how ageing by itself contributes to development of macular disease.

Macular thickness and macular volume measurements using spectral domain optical coherence tomography in normal Nepalese eyes

PURPOSE

To record the normative values for macular thickness and macular volume in normal Nepalese eyes.

METHODS

In all, 126 eyes of 63 emmetropic subjects (mean age: 21.17±6.76 years; range: 10-37 years) were assessed for macular thickness and macular volume, using spectral domain-optical coherence tomography over 6×6 mm(2) in the posterior pole. A fast macular thickness protocol was employed. Statistics such as the mean, median, standard deviation, percentiles, and range were used, while a P-value was set at 0.05 to test significance.

RESULTS

Average macular thickness and total macular volume were larger in males compared to females. With each year of increasing age, these variables decreased by 0.556 μm and 0.0156 mm(3) for average macular thickness and total macular volume, respectively. The macular thickness was greatest in the inner superior section and lowest at the center of the fovea. The volume was greatest in the outer nasal section and thinnest in the fovea. The central subfield thickness (r=-0.243, P=0.055) and foveal volume (r=0.216, P=0.09) did not correlate with age.

CONCLUSION

Males and females differ significantly with regard to macular thickness and macular volume measurements. Reports by other studies that the increase in axial length reduced thickness and volume, were negated by this study which found a positive correlation among axial length, thickness, and volume.

Comparison and interchangeability of macular thickness measured with Cirrus OCT and Stratus OCT in myopic eyes

AIM

To investigate the difference of macular thickness measurements between stratus optical coherence tomography (OCT) and Cirrus OCT (Carl Zeiss Meditec, Dublin, CA, USA) in the same myopic patient and to develop a conversion equation to interchange macular thickness obtained with these two OCT devices.

METHODS

Eighty-nine healthy Chinese adults with spherical equivalent (SE) ranging from -1.13 D to -9.63 D were recruited. The macular thickness was measured by Cirrus OCT and Stratus OCT. The correlation between macular thickness and axial length and the agreement between two OCT measurements were evaluated. A formula was generated to interchange macular thickness obtained with two OCT devices.

RESULTS

Average macular thickness measured with Stratus OCT (r=-0.280, P=0.008) and Cirrus OCT (r=-0.224, P=0.034) were found to be negatively correlated with axial length. No statistically significant correlation was found between axial length and central subfield macular thickness (CMT) measured with Stratus OCT (r=0.191, P=0.073) and Cirrus OCT (r=0.169, P=0.113). The mean CMT measured with Cirrus OCT was 53.63±7.94 µm thicker than with Stratus OCT. The formula CMTCirrus OCT=78.328+0.874×CMTStratus OCT was generated to interchange macular thickness obtained with two OCT devices.

CONCLUSION

Macular thickness measured with Cirrus OCT were thicker than with Stratus OCT in myopic eyes. A formula can be used to interchange macular thickness measured with two OCT devices in myopic eyes. Studies with different OCT devices and larger samples are warranted to enable the comparison of macular values measured with different OCT devices.

Repeatability of Foveal Measurements Using Spectralis Optical Coherence Tomography Segmentation Software

Purpose

To investigate repeatability and reproducibility of thickness of eight individual retinal layers at axial and lateral foveal locations, as well as foveal width, measured from Spectralis spectral domain optical coherence tomography (SD-OCT) scans using newly available retinal layer segmentation software.

Methods

High-resolution SD-OCT scans were acquired for 40 eyes of 40 young healthy volunteers. Two scans were obtained in a single visit for each participant. Using new Spectralis segmentation software, two investigators independently obtained thickness of each of eight individual retinal layers at 0°, 2° and 5° eccentricities nasal and temporal to foveal centre, as well as foveal width measurements. Bland-Altman Coefficient of Repeatability (CoR) was calculated for inter-investigator and inter-scan agreement of all retinal measurements. Spearman's ρ indicated correlation of manually located central retinal thickness (RT₀) with automated minimum foveal thickness (MFT) measurements. In addition, we investigated nasal-temporal symmetry of individual retinal layer thickness within the foveal pit.

Results

Inter-scan CoR values ranged from 3.1μm for axial retinal nerve fibre layer thickness to 15.0μm for the ganglion cell layer at 5° eccentricity. Mean foveal width was 2550μm ± 322μm with a CoR of 13μm for inter-investigator and 40μm for inter-scan agreement. Correlation of RT₀ and MFT was very good (ρ = 0.97, P < 0.0005). There were no significant differences in thickness of any individual retinal layers at 2° nasal compared to temporal to fovea (P > 0.05); however this symmetry could not be found at 5° eccentricity.

Conclusions

We demonstrate excellent repeatability and reproducibility of each of eight individual retinal layer thickness measurements within the fovea as well as foveal width using Spectralis SD-OCT segmentation software in a young, healthy cohort. Thickness of all individual retinal layers were symmetrical at 2°, but not at 5° eccentricity away from the fovea.

Normative spectral domain optical coherence tomography data on macular and retinal nerve fiber layer thickness in Indians

Aim:

To provide the normative data of macular and retinal nerve fiber layer (RNFL) thickness in Indians using spectral domain OCT (Spectralis OCT, Heidelberg Engineering, Germany) and to evaluate the effects of age, gender, and refraction on these parameters.

Design:

Observational, cross-sectional study.

Materials and Methods:

The eyes of 105 healthy patients aged between 20-75 years, with no ocular disease and best corrected visual acuity of 20/20, were scanned using standard scanning protocols by a single examiner. Exclusion criteria included glaucoma, retinal diseases, diabetes, history of prior intraocular surgery or laser treatment. The mean macular and RNFL thickness were recorded, and the effects of age, gender, and refraction on these parameters were evaluated. This data was compared with published literature on Caucasians to assess the ethnic variations of these parameters.

Results:

The normal central foveal thickness in healthy Indian eyes measured using Spectralis OCT was 260.1 ± 18.19 μm. The nasal inner quadrant showed maximum retinal thickness (338.88 ± 18.17 μm). The mean RNFL thickness was 101.43 ± 8.63 μm with maximum thickness in the inferior quadrant. The central foveal thickness showed a gender-based difference (P = 0.005) but did not correlate significantly with age (P = 0.134), whereas the parafoveal, perifoveal thickness, macular volume, and RNFL thickness showed significant negative correlation with age.

Conclusions:

Our study provides the normative database for Indians on Spectralis OCT. It also suggests that age should be considered while interpreting the macular thickness and RNFL, whereas gender should also be given consideration in central foveal thickness.

Retinal thickness in black and Indian myopic students at the University of KwaZulu-Natal

Background: It has been suggested that retinal thickness varies with demographic variables. Understanding the influence of demographic variables on retinal thickness could improve our knowledge of risk factors for retinal pathologies. Previous studies have focused exclusively on white and African-American populations, with limited attention to black and Indian populations.Aim: To compare retinal thickness in black and Indian myopic students at the University of KwaZulu-Natal (UKZN).Methods: A cross-sectional comparative research design was used. The study was conducted at UKZN, Westville campus. Retinal thickness was measured in 80 healthy myopic students using the Fourier/spectral domain iVue 100 optical coherence tomographer. Retinal thickness measurements of the right and left eyes showed significant correlations, therefore data from only the right eyes were analysed. Racial and gender variations in retinal thickness of the nine Early Treatment Diabetic Retinopathy Study (ETDRS) segments were assessed.Results: The mean central foveal thickness in black participants was 238 μm compared with 243 μm in Indian participants (p = 0.06). Indian participants had thicker parafoveal thickness measurements whilst black participants had thicker perifoveal thickness measurements. Male participants had thicker retinal thickness measurements in all nine ETDRS segments than female participants. Central foveal thickness showed no significant correlation with spherical equivalent (r = -0.14, p > 0.05) or axial length (r = 0.09, p > 0.05).Conclusion: The average central foveal thickness was slightly thinner in black and female participants than in Indian and male participants. Optometrists and ophthalmologists should consider these differences when evaluating black and Indian individuals with foveal retinal diseases.

Symmetry of retinal parameters measured by spectral-domain OCT in normal young adults

PURPOSE

To determine interocular differences in retinal parameters in a population of young adults using spectral-domain optical coherence tomography.

METHODS

In the Sydney Adolescent Vascular Eye Study, young adults aged 16 to 19 years received a standardized eye examination encompassing retinal photography, spectral-domain optical coherence tomography (Cirrus HD-OCT; Carl Zeiss Meditec, Dublin, CA) and best-corrected visual acuity. Interocular differences in retinal nerve fiber layer (RNFL) and macular parameters together with sex and ethnic variations for these differences were determined.

RESULTS

In the 1500 subjects tested, right eyes had thicker average RNFL than left eyes (0.3 μm, P=0.0074). There were no significant interocular differences in central macular or macular cube average thickness. After adjusting for interocular difference in axial length, right eyes had slightly smaller total macular volume than left eyes (-0.0082 mm, P=0.008). The 2.5% to 97.5% limits of asymmetry were 9.3 μm for average RNFL, 8 μm for average macular thickness, and 0.20 mm for total macular volume. In the outer inferior quadrant, there was a greater macular thickness asymmetry in females than males (-0.7 μm, P=0.037). In the inferior RNFL quadrant (-2.6 μm, P=0.0013) and in the outer inferior macular quadrant (1.6 μm, P=0.0018), white individuals had greater symmetry than East Asians.

CONCLUSIONS

In this study, we report the degree of interocular symmetry of RNFL and macular parameters measured by Cirrus HD-OCT in healthy young adults.

Between-subject variability in asymmetry analysis of macular thickness

PURPOSE

To investigate the use of asymmetry analysis to reduce between-subject variability of macular thickness measurements using spectral domain optical coherence tomography.

METHODS

Sixty-three volunteers (33 young subjects [aged 21 to 35 years] and 30 older subjects [aged 45 to 85 years]) free of eye disease were recruited. Macular images were gathered with the Spectralis optical coherence tomography. An overlay 24- by 24-degree grid was divided into five zones per hemifield, and asymmetry analysis was computed as the difference between superior and inferior zone thicknesses. We hypothesized that the lowest variation and the highest density of ganglion cells will be found approximately 3 to 6 degrees from the foveola, corresponding to zones 1 and 2. For each zone and age group, between-subject SDs were compared for retinal thickness versus asymmetry analysis using an F test. To account for repeated comparisons, p < 0.0125 was required for statistical significance. Axial length and corneal curvature were measured with an IOLMaster.

RESULTS

For OD, asymmetry analysis reduced between-subject variability in zones 1 and 2 in both groups (F > 3.2, p < 0.001). Standard deviation for zone 1 dropped from 12.0 to 3.0 μm in the young group and from 11.7 to 2.6 μm in the older group. Standard deviation for zone 2 dropped from 13.6 to 5.3 μm in the young group and from 11.1 to 5.8 μm in the older group. Combining all subjects, neither retinal thickness nor asymmetry analysis showed a strong correlation with axial length or corneal curvature (R² < 0.01). Analysis for OS yielded the same pattern of results, as did asymmetry analyses between eyes (F > 3.8, p < 0.0001).

CONCLUSIONS

Asymmetry analysis reduced between-subject variability in zones 1 and 2. Combining the five zones together produced a higher between-subject variation of the retinal thickness asymmetry analysis; thus, we encourage clinicians to be cautious when interpreting the asymmetry analysis printouts.

Interocular amplitude and latency differences of pattern ERG and pattern VEP parameters

PURPOSE

To determine the normal interocular differences in amplitudes and peak times of the pattern electroretinograms (PERGs) and pattern visual evoked potentials (PVEPs) and to investigate whether the PERG and PVEP parameters correspond in lateral dominance or whether the eye-side distributions of the functional parameters are similar.

METHODS

The PERGs and PVEPs were recorded in healthy subjects (N = 77) according to the standards of the International Society for Clinical Electrophysiology of Vision, with the modification of the check size of the PERG to 0.5 degrees. This allows stimulation of the macular ganglion cells and their corresponding visual pathways in healthy subjects.

RESULTS

Comparison of the averaged higher and lower response amplitudes and the shorter and longer response peak times showed significant differences (p < 0.001) in both the PERG and the PVEP parameters (median [5 to 95%]): the P50 (1.92% [0 to 5.48%]) and N95 (2.06% [0 to 13.95%]) peak times and the P50 (11.82% [1.32 to 29.93%) and N95 (9.45% [1.17 to 30.38%]) amplitudes of the PERGs and the P100 (1.04% [0 to 4.15%]) and N135 (1.96% [0 to 12.36%]) peak times and the P100 (9.86% [1.26 to 29.76%]) and N135 (11.19% [1.18 to 29.99%]) amplitudes of the PVEPs. No significant correlation was found concerning the eye dominance of the PERG and PVEP parameters.

CONCLUSIONS

Our results reveal a significant interocular difference on PERG and PVEP recording, but this could not be ascribed to the anatomy of the retina and related visual pathways. If the difference between the eyes is not taken into account, misinterpretation may occur in a pathological process.

Measurement of retinal thickness in macular region of high myopic eyes using spectral domain OCT

AIM

To investigate the changes of retinal thickness in macula of high myopic eyes using spectral domain optical coherence tomography (OCT).

METHODS

Middle-aged and young myopic patients were divided into three groups according to their refractive error/axial length: low and medium myopia group (LMMG), high myopia group (HMG) and super high myopia group (SHMG). Cirrus HD-OCT was used to evaluate total average macular thickness, central subfield thickness, inner/outer macular thickness and macular volume. The differences among experimental groups were analyzed by one-factor analysis of variance. Associations between macular thickness and refractive error/axial length were analyzed by Pearson correlation analysis.

RESULTS

There was no significant difference in age among the three groups (P=0.2789). The mean refraction error in the LMMG, HMG, and SHMG groups was -2.49±1.38D, -8.53±1.95D and -13.88±1.76D, respectively (P<0.001). The central subfield thickness of three groups was 244.56±12.19µm, 254.33±11.61µm and 261.75±11.83µm, respectively, and there were statistically significance between random two groups. The total average macular thickness, inner/outer macular thickness, and macular volume decreased with increased myopia/axial length. Average foveal thickness had negative correlations with refractive error (P<0.001), and positive correlations with axial length. The inferior and temporal inner macular thickness, all the quadrants of outer ring, total average macular thickness and macular volume featured positive correlations with refractive error, and negative correlations with axial length. Average foveal thickness, superior and temporal inner macular thicknesses, and temporal outer macular thickness was lower in females compared to males.

CONCLUSION

With an increase in myopia degree/axial length, the average foveal thickness increased and the inner/outer macular thickness decreased. Females featured thicker average foveal thickness, and thinner macular thickness compared to males.

Diagnostic precision of retinal nerve fiber layer and macular thickness asymmetry parameters for identifying early primary open-angle glaucoma

PURPOSE

To evaluate the diagnostic capabilities of intereye and intraeye differences in retinal nerve fiber layer (RNFL) thickness and macular thickness for identifying early primary open-angle glaucoma (POAG).

DESIGN

Prospective, cross-sectional cohort study.

METHODS

All subjects were enrolled from an ongoing institutional glaucoma study. We used spectral-domain optical coherence tomography (Spectralis; Heidelberg Engineering) to obtain macular thickness (posterior pole asymmetry scan) and RNFL thickness (circumpapillary scan) in both eyes of 50 early POAG and 50 control subjects. Early POAG subjects had glaucomatous optic neuropathy with mild, reproducible visual field loss in at least 1 eye, and control subjects had normal intraocular pressures, visual fields, and optic nerves. We recorded total, superior, and inferior RNFL and macular thicknesses and then calculated intereye and intraeye differences (asymmetry parameters). Statistical evaluation included receiver operating characteristic and multivariate logistic regression analyses.

RESULTS

Intereye macular thickness asymmetry had the highest diagnostic sensitivity (88% at 80% specificity; 83% at 95% specificity), followed by total RNFL thickness (88% at 80% specificity; 75% at 95% specificity). Parameters with the largest areas under the receiver operating characteristic curves were: total RNFL thickness (0.937), intereye RNFL asymmetry (0.921), intereye macular thickness asymmetry (0.913), inferior RNFL thickness (0.905), superior RNFL thickness (0.887), intereye inferior macular thickness asymmetry (0.872), and intraeye macular thickness asymmetry (0.860). These 7 values were not significantly different. In multivariate logistic regression analyses, intraeye macular thickness asymmetry, intereye macular thickness asymmetry, intereye RNFL thickness asymmetry, and total RNFL thickness were related independently to early POAG.

CONCLUSIONS

Structural asymmetry parameters performed well, identifying early POAG as well as RNFL thickness. Further study is indicated to validate these results.

Retinal nerve fibre layer thickness and macular thickness in patients with esotropic amblyopia

BACKGROUND

The objective of this study was to evaluate the retinal nerve fibre layer thickness (RNFLT) and retinal macular thickness (RMT) in esotropic amblyopic children.

METHODS

Twenty-one children diagnosed with esotropic amblyopia at Strabismus and Amblyopia Department of Wenzhou Medical College Affiliated Eye Hospital, China, were enrolled in the study. Their fellow eyes were normal and were used as controls. RNFLT and RMT were measured by optical coherence tomography (OCT).

RESULTS

The fovea and the central sector of the retina in amblyopic eyes were slightly but not significantly thicker than those in the normal fellow eyes. There was no significant difference in any section of macular thickness between amblyopic and fellow eyes (p > 0.05). In addition, no significant differences in thickness were found between the retinal nerve fibre layers of amblyopic and normal fellow eyes (p > 0.05).

CONCLUSION

There were no differences in the thickness of the foveal and the retinal nerve fibre layers found between eyes with esotropic amblyopia and the normal fellow eyes in children aged seven to 14 years.

Prospective three-dimensional analysis of structure and function in vitreomacular adhesion cured by pharmacologic vitreolysis

PURPOSE

To prospectively characterize macular structure and function as assessed by combined three-dimensional spectral-domain optical coherence tomography and scanning laser ophthalmoscopy and 3D computer-automated threshold Amsler grid, respectively, in a patient undergoing pharmacologic vitreolysis for vitreomacular adhesion with tractional cysts.

METHODS

Combined 3D optical coherence tomography and scanning laser ophthalmoscopy measured macular volume and 3D computer-automated threshold Amsler grid quantified central visual field function by determining the absolute percent magnitude lost (cumulative value of total visual field loss over all tested levels) before and for a period of 6 months after pharmacologic vitreolysis for vitreomacular adhesion with a single intravitreal injection of microplasmin (125 μg; ThromboGenics).

RESULTS

Ocriplasmin pharmacologic vitreolysis released vitreomacular adhesion by 2 weeks and decreased macular volume from 0.32 μL to 0.15 μL by 1 year after injection. There was a concomitant 4-fold improvement in visual function as measured by 3D computer-automated threshold Amsler grid (percent of central visual field lost) and Snellen visual acuity improved from 20/200 to 20/40.

CONCLUSION

For assessing macular function improvement in conjunction with structural reintegration after pharmacologic vitreolysis for vitreomacular adhesion, 3D computer-automated threshold Amsler grid is a useful tool. Both 3D measurements quantitatively characterized the resolution of this patient's vitreomacular adhesion, suggesting that this is a useful approach to quantifying macular structure and function as indices of the severity of disease and the response to therapy.

Discrepancies between fluorescein angiography and optical coherence tomography in macular edema in uveitis

PURPOSE

To assess the frequency and characteristics of discrepant findings between fluorescein angiography (FA) and optical coherence tomography (OCT) in uveitic macular edema (ME).

DESIGN

Retrospective cross-sectional study of 112 eyes of 78 patients with uveitic ME on FA, OCT, or both.

METHODS

ME was graded on OCT and FA of uveitis patients attending the University Medical Center Utrecht. The frequency and severity of discrepant findings were analyzed, and the clinical findings at the time of imaging were assessed. The imaging studies were compared with the clinical characteristics.

RESULTS

Positive results of both imaging methods (FA+/OCT+) were observed in 61 (54%) of 112 eyes, whereas discrepant results occurred in 51 (46%) of 112 eyes. The FA+/OCT- discrepancy occurred in 34 (30%) of 112 eyes, and the FA-/OCT+ discrepancy occurred in 17 (15%) of 112 eyes. No correlations between the discrepant imaging results and age, gender, duration of uveitis or ME, visual acuity, or cause of uveitis were identified. FA+/OCT- and FA-/OCT+ discrepancies comprised typically mild degrees of ME. The FA+/OCT- discrepancy occurred in 50% of eyes with birdshot chorioretinopathy (7/14), and the FA-/OCT+ discrepancy occurred more often in intermediate uveitis than in other anatomic locations. Although the FA+/OCT+ consistency was noted frequently in active uveitis, the FA-/OCT+ discrepancy was common in eyes with inactive uveitis (8/18; 44% of inactive eyes).

CONCLUSIONS

Our results emphasize that FA and OCT are complementary investigations, each revealing different aspects of the pathophysiology of uveitic ME.

Ethnic differences in macular thickness

BACKGROUND

To determine ethnic differences in time-domain (Stratus) optical coherence tomography-measured macular thickness in 12-year-old children.

DESIGN

Population-based cross-sectional study.

PARTICIPANTS

A total of 2367 children from grade 7 (mean age 12.7 ± 0.45 years) examined during the Sydney Myopia Study during 2004-2005.

METHODS

Examination included determination of best corrected visual acuity. Autorefraction was performed after cycloplegia. Axial length was measured using non-contact interferometry and OCT was performed using Stratus OCT. Ethnicity was self reported by participants' parents.

MAIN OUTCOME MEASURES

Macular thickness.

RESULTS

The four largest ethnic groups were Caucasian (n = 1224), East Asian (n = 291), South Asian (n = 107) and Middle Eastern (n = 146). The greatest ethnic differences were found at the central macula, which was significantly thicker in Caucasian compared with East Asian, South Asian and Middle Eastern children (mean differences 9.0 µm, 12.1 µm and 6.5 µm, respectively; all P < 0.0001). The average inner macula was significantly thicker in Caucasian than East Asian and South Asian children (P = 0.005 and P < 0.0001, respectively). The average outer macula was significantly thicker in Caucasian than Middle Eastern and South Asian children (P = 0.03 and P < 0.0001, respectively).

CONCLUSION

Macular parameters were found to vary by ethnicity in 12-year-old children. Caucasian children had the thickest macular parameters and South Asian children had the thinnest. The greatest differences were found in the central macula.

Race- and sex-related differences in retinal thickness and foveal pit morphology

PURPOSE

To examine sex- and race-associated differences in macular thickness and foveal pit morphology by using spectral-domain optical coherence tomography (SD-OCT).

METHODS

One hundred eighty eyes of 90 healthy patients (43 women, 47 men) underwent retinal imaging with spectral-domain OCT. The lateral scale of each macular volume scan was corrected for individual differences in axial length by ocular biometry. From these corrected volumes, Early Treatment Diabetic Retinopathy Study (ETDRS) grids of retinal thickness were generated and compared between the groups. Foveal morphology was measured with previously described algorithms.

RESULTS

Compared with the Caucasians, the Africans and African Americans had reduced central subfield thickness. Central subfield thickness was also reduced in the women compared with the men, although the women also showed significant thinning in parafoveal regions. There was no difference between the sexes in foveal pit morphology; however, the Africans/African Americans had significantly deeper and broader foveal pits than the Caucasians.

CONCLUSIONS

Previous studies have reported race- and sex-associated differences in macular thickness, and the inference has been that these differences represent similar anatomic features. However, the data on pit morphology collected in the present study reveal an important and significant variation. Between the sexes, the differences are due to global variability in retinal thickness, whereas the variation in thickness observed between the races appears to be driven by differences in foveal pit morphology. These differences have important implications for the use of SD-OCT in detecting and diagnosing retinal disease.

Macular thickness measurements in healthy Norwegian volunteers: an optical coherence tomography study

BACKGROUND

Ethnic, intersubject, interoperator and intermachine differences in measured macular thickness seem to exist. Our purpose was to collect normative macular thickness data in Norwegians and to evaluate the association between macular thickness and age, gender, parity, and contraception status.

METHODS

Retinal thickness was measured by Stratus Optical Coherence Tomography in healthy subjects. Mean macular thickness (MMT) was analyzed by repeated measures ANOVA with three dependent regional MMT-variables for interaction with age, gender, parity and oral contraception use. Exploratory correlation with age by the Pearson correlation test, both before and after stratification by gender was performed. Differences in MMT between older and younger subjects, between oral contraception users and non-users, as well as parous and nulliparous women were studied by post-hoc Student's t-tests.

RESULTS

Central MMT in Norwegians was similar to values earlier reported in whites. MMT in central areas of 1 and 2.25 mm in diameter were higher in males than in females. In younger subjects (< or =43 years) differences in MMT between genders were larger than in the mixed age group, whereas in older subjects (>43 years) the small differences did not reach the set significance level. No differences were found in minimal foveolar thickness (MMFT) between the genders in any age group.Mean foveal thickness (1 mm in diameter) was positively associated with age in females (r = 0.28, p = 0.03). MMFT was positively associated with age in all groups and reached significance both in females and in mixed gender group (r = 0.20, p = 0.041 and r = 0.26, p = 0.044 respectively).Mean foveal thickness and MMFT were significantly higher in parous than in nulliparous women, and age-adjusted ANOVA for MMFT revealed a borderline effect of parity.

CONCLUSIONS

Age and gender should be taken into consideration when establishing normal ranges for MMT in younger subjects. The gender difference in retinal thickness in young, but not older adults suggests a gonadal hormonal influence. The possible association between parity and retinal structure and its clinical relevance, should be studied further.

Intravitreal ranibizumab (Lucentis) for treatment of central retinal vein occlusion: a prospective study

BACKGROUND/PURPOSE

To evaluate the effect of individualized repeated intravitreal injections of ranibizumab (Lucentis) on visual acuity (VA) and central foveal thickness (CFT) for central retinal vein occlusion (CRVO)-induced macular edema.

METHODS

Our study was a prospective interventional case series. Twelve eyes of 12 consecutive patients diagnosed with CRVO-related macular edema (nine perfused, three ischemic CRVO) treated with repeated (when CFT was >220 microm) intravitreal injections of ranibizumab as a monotherapy within 3 months of onset were evaluated. Optical coherence tomography (OCT) and fluorescein angiography (FA) were performed monthly and every 3 months respectively. Changes in VA (ETDRS) and CFT were analyzed using the student's paired t-test.

RESULTS

The mean time from diagnosis until injection was 80 days (2.7 months; range, 63-90 days) and the follow-up time was 12 months. In total, 89 injections were performed (mean 7.4). The mean CFT improved from 480 +/- 166 microm at baseline to 230 +/- 33 microm (P < 0.001) at the end of the follow-up. During the same period, of the 12 eyes, eight demonstrated improved VA (>0.3 LogMAR change, >15 letters), three stable VA and one worse VA as compared to baseline. None of the nine patients with perfused CRVO were converted to ischemic at 12 months, and one of the three eyes with ischemic CRVO developed iris neovascularization despite two ranibizumab injections. No ocular or systemic side-effects were noted.

CONCLUSION

Individualized repeated intravitreal injections of ranibizumab have shown promising results in VA improvement and decrease in CFT in patients with macular edema associated with CRVO. Further studies are needed in order to elucidate the role of intravitreal lucentis in the ischemic form of CRVO, and its efficacy in preventing conversion from the perfused to the ischemic form of the disease.