Normative data and repeatability for macular ganglion cell layer thickness in healthy Swedish children using swept source optical coherence tomography.

BACKGROUND: Optical coherent tomography (OCT) technology is evolving with improved resolution and accuracy in segmentation between different cell layers in the retina. The ganglion cell layer in the macula region is a window to see what is happening in the visual pathways and a macula OCT is an examination that most children tolerate. This makes updated normative data necessary since variables may differ between different OCT devices and normative data for children is often not presented. The aim of this study was to develop normative data for macular ganglion cell layer thickness in children, measured with swept source OCT, and investigate the repeatability between measurements. METHODS: Healthy Swedish children between 4 and 16 years old, with normal refraction, spherical equivalent mean:1.13 (sd:0.66) dioptre and normal visual acuity Logmar, mean: 0,015 (sd:0,05), were examined with swept source OCT. Macula OCT was performed three times in both eyes and the different retinal layers were evaluated. RESULTS: Fifty-eight children were screened for inclusion. Fifty-five children were included in the study, 24 boys and 31 girls. Mean age was 8.9 years. Results from right eyes was analysed. The mean average thickness of macular ganglion cell layer thickness, retinal nerve fibre layer/ganglion cell layer boundary to inner plexiform layer/inner nuclear layer boundary, was 68.0 µm (sd:4.0, range:58-77). There was no correlation with sex or age. Fifty-three children manage to complete two, and 41 children three acceptable measurement and the mean coefficient of variation was low. CONCLUSION: The ganglion cell layer thickness differs according to which OCT device that is used, and the population examined. This makes normative data essential to accurately interpret results. Swept source OCT of the macula have excellent repeatability and the examination well tolerated in most children making it an investigation useful for diagnosing and following diseases in the optic pathways.

Retinal nerve fibre layer and ganglion cell layer changes in children who recovered from COVID-19: a cohort study.

OBJECTIVE: To investigate the optic nerve and macular parameters of children who recovered from COVID-19 compared with healthy children using optical coherence tomography (OCT). DESIGN: Cohort study. SETTING: Hospital Clinico San Carlos, Madrid. PATIENTS: Children between 6 and 18 years old who recovered from COVID-19 with laboratory-confirmed SARS-CoV-2 infection and historical controls were included. INTERVENTIONS: All patients underwent an ophthalmological examination, including macular and optic nerve OCT. Demographic data, medical history and COVID-19 symptoms were noted. MAIN OUTCOME MEASURES: Peripapillary retinal nerve fibre layer thickness, macular retinal nerve fibre layer thickness, macular ganglion cell layer thickness and retinal thickness. RESULTS: 90 patients were included: 29 children who recovered from COVID-19 and 61 controls. Patients with COVID-19 presented an increase in global peripapillary retinal nerve fibre layer thickness (mean difference 7.7; 95% CI 3.4 to 12.1), temporal superior (mean difference 11.0; 95% CI 3.3 to 18.6), temporal inferior (mean difference 15.6; 95% CI 6.5 to 24.7) and nasal (mean difference 9.8; 95% CI 2.9 to 16.7) sectors. Macular retinal nerve fibre layer analysis showed decreased thickness in the nasal outer (p=0.011) and temporal inner (p=0.036) sectors in patients with COVID-19, while macular ganglion cell layer thickness increased in these sectors (p=0.001 and p=0.015, respectively). No differences in retinal thickness were noted. CONCLUSIONS: Children with recent history of COVID-19 present significant changes in peripapillary and macular OCT analyses.

Involvement of Anoikis in Dissociated Optic Nerve Fiber Layer Appearance.

Dissociated optic nerve fiber layer (DONFL) appearance is characterized by dimpling of the fundus when observed after vitrectomy with the internal limiting membrane (ILM) peeling in macular diseases. However, the cause of DONFL remains largely unknown. Optical coherence tomography (OCT) findings have indicated that the nerve fiber layer (NFL) and ganglion cells are likely to have been damaged in patients with DONFL appearance. Since DONFL appearance occurs at a certain postoperative period, it is unlikely to be retinal damage directly caused by ILM peeling because apoptosis occurs at a certain period after tissue damage and/or injury. However, it may be due to ILM peeling-induced apoptosis in the retinal tissue. Anoikis is a type of apoptosis that occurs in anchorage-dependent cells upon detachment of those cells from the surrounding extracellular matrix (i.e., the loss of cell anchorage). The anoikis-related proteins ßA3/A1 crystallin and E-cadherin are reportedly expressed in retinal ganglion cells. Thus, we theorize that one possible cause of DONFL appearance is ILM peeling-induced anoikis in retinal ganglion cells.

Altered photoreceptor metabolism in mouse causes late stage age-related macular degeneration-like pathologies.

Age-related macular degeneration (AMD) is the leading cause of blindness in the elderly. While the histopathology of the different disease stages is well characterized, the cause underlying the progression, from the early drusen stage to the advanced macular degeneration stage that leads to blindness, remains unknown. Here, we show that photoreceptors (PRs) of diseased individuals display increased expression of two key glycolytic genes, suggestive of a glucose shortage during disease. Mimicking aspects of this metabolic profile in PRs of wild-type mice by activation of the mammalian target of rapamycin complex 1 (mTORC1) caused early drusen-like pathologies, as well as advanced AMD-like pathologies. Mice with activated mTORC1 in PRs also displayed other early disease features, such as a delay in photoreceptor outer segment (POS) clearance and accumulation of lipofuscin in the retinal-pigmented epithelium (RPE) and of lipoproteins at the Bruch's membrane (BrM), as well as changes in complement accumulation. Interestingly, formation of drusen-like deposits was dependent on activation of mTORC1 in cones. Both major types of advanced AMD pathologies, including geographic atrophy (GA) and neovascular pathologies, were also seen. Finally, activated mTORC1 in PRs resulted in a threefold reduction in di-docosahexaenoic acid (DHA)-containing phospholipid species. Feeding mice a DHA-enriched diet alleviated most pathologies. The data recapitulate many aspects of the human disease, suggesting that metabolic adaptations in photoreceptors could contribute to disease progression in AMD. Identifying the changes downstream of mTORC1 that lead to advanced pathologies in mouse might present new opportunities to study the role of PRs in AMD pathogenesis.

Interobserver reproducibility and interocular symmetry of the macular ganglion cell complex: assessment in healthy children using optical coherence tomography.

BACKGROUND: Assessment of interobserver reproducibility and interocular symmetry using optical coherence tomography (OCT)-based measurements of the macular ganglion cell complex (GCC) in healthy children facilitates interpretation of OCT data. We assessed the interobserver reproducibility and interocular symmetry of GCC and evaluated candidate determinants. METHODS: This was a cross-sectional study performed in a primary and tertiary health-care setting. A total of 126 healthy participants aged 5 to 18 years were eligible. GCC scans were performed by 4 operators using the Topcon 3D OCT-2000 device. Intraclass correlation coefficients (ICCs) were used to estimate reproducibility and symmetry. Cut-off points for symmetry were defined as the 95th percentile of the absolute interocular difference for 6 GCC parameters. Percentile distributions of interocular difference were generated based on age and difference in absolute interocular spherical equivalent (SE). RESULTS: The reproducibility ICC ranged from 0.96 to 0.98 for all 6 GCC parameters. Cut-off points for interocular symmetry of the superior and inferior quadrants and total macular retinal nerve fibre layer thickness (mRNFL) and macular ganglion cell layer-inner plexiform layer thickness were 3.5, 4.5, 3.0, 3.0, 2.5, and 2.5 µm respectively. A positive association was observed between the absolute interocular difference of SE and superior and total mRNFL symmetry values (p = 0.047 and p = 0.040, respectively). CONCLUSIONS: OCT measurements of GCC in healthy children show excellent reproducibility. Interocular differences in SE should be assessed when mRNFL differences exceed the 95% cut-off. These findings can contribute to establish reference values for interocular symmetry in paediatric GCC parameters.

Age-related changes in and determinants of macular ganglion cell-inner plexiform layer thickness in normal Chinese adults.

IMPORTANCE: Consideration of age-related changes in macular ganglion cell-inner plexiform layer (mGCIPL) thickness are important for glaucoma progression analysis. BACKGROUND: To report age-related changes in and the determinants of high-definition optical coherence tomography (HD-OCT) measurements of mGCIPL thickness. DESIGN: Cross-sectional study. PARTICIPANTS: 326 healthy adults. METHODS: All subjects underwent Cirrus HD-OCT measurements of mGCIPL. One-way analysis of variance (ANOVA) was used to compare mGCIPL thickness between 7 decades based age groups and macular sectors. Multiple regression analysis determined the association between mGCIPL thickness and age, gender, intraocular pressure (IOP), peripapillary retinal nerve fibre layer thickness (pRNFL) and spherical equivalent. MAIN OUTCOME MEASURES: Change in mGCIPL thickness and determinants of thickness. RESULTS: Mean mGCIPL thickness in 295 subjects was 80.80 ± 6.42 µm. Mean mGCIPL decreased by 0.12 µm (95% CI [confidence interval], 0.09-0.16) with every year of age; 1.61 µm (95% CI, 0.08-2.41) per decade. It showed two steep declines with age, first in the fifth and next in the seventh decade with relative stability between them. mGCIPL thickness was associated with pRNFL thickness (ß = 0.30, P < 0.001) and IOP (ß = -0.19, P = 0.03) but not with gender (ß = -1.09, P = 0.116) or spherical equivalent (ß = -0. 24, P = 0.145). CONCLUSIONS AND RELEVANCE: Mean mGCIPL thickness showed a small age-related linear decrease with two steep drops in the fifth and seventh decades. Thinner mGCIPL was independently associated with age, thinner pRNFL and higher IOP. These factors should be considered if using mGCIPL to detect progression of glaucoma and other optic neuropathies characterized by the loss of retinal ganglion cells.

Increased levels of circulating CD34+ cells in neovascular age-related macular degeneration: relation with clinical and OCT features.

PURPOSE: To investigate the levels of circulating CD34+ stem cells in patients with neovascular type age-related macular degeneration (AMD) and its relation with clinical and optical coherence tomography (OCT) findings. METHODS: The study consisted of 55 patients: 28 patients (18 male and 10 female) with neovascular type AMD as a study group and 27 patients (12 male and 15 female) scheduled for cataract surgery as a control group. The level of CD34+ stem cells was measured by flow cytometry. Demographic and clinical data were recorded. RESULTS: The mean ages of patients in the study and control groups were 71 ± 8 and 68 ± 6 years, respectively. There was no statistically significant difference in terms of age, sex, or systemic disease association between study and control groups. However, smoking status was significantly higher in the study group (67.9% vs 37.0%; p = 0.02). Stem cell levels were significantly higher in the study group (1.5 ± 0.9 vs 0.5 ± 0.3; p<0.001), but there was no relation between stem cell levels and clinical and OCT findings. CONCLUSIONS: Increased circulating CD34+ stem cell levels were observed in patients with choroidal neovascular membrane associated with AMD, but no significant relation was found between cell levels and clinical and OCT findings.

Effects of Selective Serotonin Reuptake Inhibitors on Macular Ganglion Cell Complex Thickness and Peripapillary Retinal Nerve Fiber Layer Thickness.

PURPOSE: To evaluate macular ganglion cell complex (GCC) thickness and peripapillary retinal nerve fiber layer (RNFL) thickness in patients treated with SSRIs. METHODS: The present study included 62 eyes of 31 patients who were using SSRIs and 60 eyes of 30 healthy, age- and gender-matched control subjects. All patients underwent a full ophthalmological examination in which macular thickness, GCC thickness, and peripapillary RNFL thickness were measured using optical coherence tomography (OCT). The Mann-Whitney U test was used to compare the patients' group with the age- and gender-matched control group. Pearson correlation analyses were also performed to assess the relationships between macular thickness, GCC thickness, RNFL thickness, and the duration of SSRI usage. RESULTS: The mean duration of SSRI usage was 29.96 ± 27.19 (range 6-120) months. The foveal thickness was 253.48 ± 22.77µm in the patients' group and 266.60 ± 20.64 µm in the control group; the difference between the groups was statistically significant. In addition, the perifoveal GCC thickness in the inferonasal and inferotemporal quadrant were significantly smaller thinner in the patient group (Mann-Whitney U test, p = 0.021and p = 0.013, respectively). CONCLUSIONS: Our results suggest a relation between SSRIs and decreased retinal GCC thickness and RNFL thickness. Future long-term prospective studies should elucidate the actual effect of SSRIs on GCC and RNFL thickness.

Reproducibility of macular ganglion cell-inner plexiform layer thickness in normal eyes determined by two different OCT scanning protocols.

BACKGROUND: To investigate the reproducibility of macular ganglion cell-inner plexiform layer (GCIPL) thickness measurement in normal eyes determined by different operators and two different raster scanning protocols of Cirrus high-definition optical coherence tomography (HD-OCT). METHODS: One hundred and two eyes of 102 normal subjects were scanned three times using Cirrus HD-OCT with Macular Cube 512 × 128 protocol by two operators, respectively. Three extra scans were obtained using Macular Cube 200 × 200 protocol. The average, minimum, superotemporal, superior, superonasal, inferonasal, inferior, and inferotemporal GCIPL thickness was measured. The reproducibility of the measurements was evaluated with intraclass correlation coefficients (ICC) and coefficients of variation (CoV). RESULTS: The intra-operator ICCs of macular GCIPL thickness were >0.875; and the inter-operator ICCs were 0.882 to 0.991. The intra-protocol ICCs of Macular Cube 512 × 128 and 200 × 200 protocol were 0.953 to 0.987 and 0.953 to 0.991, respectively; and the inter-protocol ICCs were 0.876 to 0.991. All CoVs were <1.5%. CONCLUSIONS: Cirrus HD-OCT can measure macular GCIPL thickness in normal eyes with excellent reproducibility. The measurements determined by Macular Cube 512 × 128 and 200 × 200 protocol were highly consistent and both protocols were eligible for macular GCIPL thickness measurement.

Macular thickness in healthy eyes of adults (N = 4508) and relation to sex, age and refraction: the Tromsø Eye Study (2007-2008).

PURPOSE: To provide sex-stratified normative data on retinal thickness and study the relationship with sex, age and refractive status. METHODS: Population-based study including 2617 women and 1891 men, aged 38-87 (mean 61 ± 8) years, without diabetes, glaucoma and retinal diseases, and spherical equivalent refraction (SER) within ±6 dioptres. Retinal thickness was measured with optical coherence tomography (spectral domain Cirrus HD-OCT). RESULTS: Women had thinner retina than men. Retinal thickness was significantly associated with refraction, where mean change in retinal thickness per 1 D increase in SER was -1.3 (0.2) µm in the fovea, 0.7 (0.1) µm in the pericentral ring and 1.4 (0.1) µm in the peripheral ring. In the fovea, there was a non-monotonic curved relationship between retinal thickness and age in both sexes with a maximum at about 60 years (p < 0.001). In the pericentral ring, the mean reduction in retinal thickness per 10-year increase was 2.7 (0.3) µm in women and 4.0 (0.4) µm in men and corresponding results in the peripheral ring were 2.3 (0.3) µm in women and 2.6 (0.4) µm in men. In both regions, there was evidence for a nonlinear pattern with an increased rate of change with higher age. There was a significant interaction between sex and age for retinal thickness of the pericentral ring (p = 0.041). CONCLUSION: Women had thinner retina than men, and thickness varied with refractive status. Retinal thickness was associated with age in all macular regions, and the rate of change in retinal thickness varied at different ages.

The long-term effect of oral isotretinoin therapy on macula ganglion cell complex thickness.

PURPOSE: To evaluate the long-term effect of oral isotretinoin therapy on macula ganglion cell complex (GCC) thickness by spectral domain optical coherence tomography (SD-OCT). MATERIALS AND METHODS: Newly diagnosed cystic acne patients who received low dose for a long time systemic isotretinoin therapy were included in this study. Thorough ophthalmic evaluation and GCC thickness analysis by using SD-OCT were performed at baseline, and at 1, 3, 6, and 12 months of treatment. RESULTS: Forty-eight eyes of 24 patients (15 females, 9 males) were included in the study. The mean age of patients was 19.37 ± 2.74 years (range 14-25 years). The full ophthalmologic examination was normal in all eyes before treatment. During the treatment there were no change in visual acuity, refractive error, intraocular pressure and tear break-up time. The mean GCC thicknesses were 81.45 ± 4.91, 81.45 ± 5.12, 81.81 ± 4.68, 81.87 ± 4.91 and 81.64 ± 5.09 µm at pretreatment and at 1, 3, 6, and 12 months of treatment, respectively (p = 0.803). CONCLUSION: One-year systemic use of isotretinoin had no significant effect on the thickness of macula ganglion cell. Macular ganglion cell analysis is useful for determining and following the toxic effects of systemic drugs on the retina. However, it is more rational to consider it as an adjunct to electrophysiological testing rather than used alone.

Macular Ganglion Cell Inner Plexiform Layer Thickness in Glaucomatous Eyes with Localized Retinal Nerve Fiber Layer Defects.

PURPOSE: To investigate macular ganglion cell-inner plexiform layer (mGCIPL) thickness in glaucomatous eyes with visible localized retinal nerve fiber layer (RNFL) defects on stereophotographs. METHODS: 112 healthy and 149 glaucomatous eyes from the Diagnostic Innovations in Glaucoma Study (DIGS) and the African Descent and Glaucoma Evaluation Study (ADAGES) subjects had standard automated perimetry (SAP), optical coherence tomography (OCT) imaging of the macula and optic nerve head, and stereoscopic optic disc photography. Masked observers identified localized RNFL defects by grading of stereophotographs. RESULT: 47 eyes had visible localized RNFL defects on stereophotographs. Eyes with visible localized RNFL defects had significantly thinner mGCIPL thickness compared to healthy eyes (68.3 ± 11.4 µm versus 79.2 ± 6.6 µm respectively, P<0.001) and similar mGCIPL thickness to glaucomatous eyes without localized RNFL defects (68.6 ± 11.2 µm, P = 1.000). The average mGCIPL thickness in eyes with RNFL defects was 14% less than similarly aged healthy controls. For 29 eyes with a visible RNFL defect in just one hemiretina (superior or inferior) mGCIPL was thinnest in the same hemiretina in 26 eyes (90%). Eyes with inferior-temporal RNFL defects also had significantly thinner inferior-temporal mGCIPL (P<0.001) and inferior mGCIPL (P = 0.030) compared to glaucomatous eyes without a visible RNFL defect. CONCLUSION: The current study indicates that presence of a localized RNFL defect is likely to indicate significant macular damage, particularly in the region of the macular that topographically corresponds to the location of the RNFL defect.

Ocular morphology and visual function in relation to general growth in moderate-to-late preterm school-aged children.

PURPOSE: To study ocular morphology and visual function in relation to general growth in moderate-to-late preterm (MLP) children. METHODS: Visual acuity (VA), refraction, optic disc parameters, biometric values and anthropometric measures were obtained from 50 eight-year-old MLP and 43 full-term children. Macular parameters were examined by optical coherence tomography. Serum insulin-like growth factor I (IGF-I) levels were analysed at birth and at assessment and delta IGF-I was calculated. RESULTS: Total macular volume was significantly less in MLP than in controls (both eyes p < 0.01). Macular volume correlated with head circumference (HCF) at assessment [right eye (RE) p = 0.002, r = 0.67; left eyes (LE) p = 0.01, r = 0.54] and refraction (both eyes p < 0.05, r = 0.4) in the MLP children. Furthermore, central retinal thickness correlated significantly with delta IGF-I (RE p = 0.03, r = -0.51, LE p = 0.006, r = -0.59) and refraction (both eyes p < 0.01, r = 0.5) and optic disc areas correlated with weight and height at assessment (all p < 0.05, r = 0.4). Total axial length correlated with HCF at assessment (both eyes p < 0.01, r = 0.5) and VA logMAR (both eyes p < 0.02, r = -0.4). CONCLUSIONS: Macular volume was significantly less in MLP children than in controls examined at 8 years of age. General growth of children and IGF-I levels seem to be involved in development of ocular growth and morphology.

Prevalence and Distribution of Segmentation Errors in Macular Ganglion Cell Analysis of Healthy Eyes Using Cirrus HD-OCT.

PURPOSE: To determine the frequency of different types of spectral domain optical coherence tomography (SD-OCT) scan artifacts and errors in ganglion cell algorithm (GCA) in healthy eyes. METHODS: Infrared image, color-coded map and each of the 128 horizontal b-scans acquired in the macular ganglion cell-inner plexiform layer scans using the Cirrus HD-OCT (Carl Zeiss Meditec, Dublin, CA) macular cube 512 × 128 protocol in 30 healthy normal eyes were evaluated. The frequency and pattern of each artifact was determined. Deviation of the segmentation line was classified into mild (less than 10 microns), moderate (10-50 microns) and severe (more than 50 microns). Each deviation, if present, was noted as upward or downward deviation. Each artifact was further described as per location on the scan and zones in the total scan area. RESULTS: A total of 1029 (26.8%) out of total 3840 scans had scan errors. The most common scan error was segmentation error (100%), followed by degraded images (6.70%), blink artifacts (0.09%) and out of register artifacts (3.3%). Misidentification of the inner retinal layers was most frequent (62%). Upward Deviation of the segmentation line (47.91%) and severe deviation (40.3%) were more often noted. Artifacts were mostly located in the central scan area (16.8%). The average number of scans with artifacts per eye was 34.3% and was not related to signal strength on Spearman correlation (p = 0.36). CONCLUSIONS: This study reveals that image artifacts and scan errors in SD-OCT GCA analysis are common and frequently involve segmentation errors. These errors may affect inner retinal thickness measurements in a clinically significant manner. Careful review of scans for artifacts is important when using this feature of SD-OCT device.

Multi-nucleate retinal pigment epithelium cells of the human macula exhibit a characteristic and highly specific distribution.

BACKGROUND: The human retinal pigment epithelium (RPE) is reportedly 3% bi-nucleated. The importance to human vision of multi-nucleated (MN)-RPE cells could be clarified with more data about their distribution in central retina. METHODS: Nineteen human RPE-flatmounts (9 ≤ 51 years, 10 > 80 years) were imaged at 12 locations: 3 eccentricities (fovea, perifovea, near periphery) in 4 quadrants (superior, inferior, temporal, nasal). Image stacks of lipofuscin-attributable autofluorescence and phalloidin labeled F-actin cytoskeleton were obtained using a confocal fluorescence microscope. Nuclei were devoid of autofluorescence and were marked using morphometric software. Cell areas were approximated by Voronoi regions. Mean number of nuclei per cell among eccentricity/quadrant groups and by age were compared using Poisson and binominal regression models. RESULTS: A total of 11,403 RPE cells at 200 locations were analyzed: 94.66% mono-, 5.31% bi-, 0.02% tri-nucleate, and 0.01% with 5 nuclei. Age had no effect on number of nuclei. There were significant regional differences: highest frequencies of MN-cells were found at the perifovea (9.9%) and near periphery (6.8%). The fovea lacked MN-cells almost entirely. The nasal quadrant had significantly more MN-cells compared to other quadrants, at all eccentricities. CONCLUSION: This study demonstrates MN-RPE cells in human macula. MN-cells may arise due to endoreplication, cell fusion, or incomplete cell division. The topography of MN-RPE cells follows the topography of photoreceptors; with near-absence at the fovea (cones only) and high frequency at perifovea (highest rod density). This distribution might reflect specific requirements of retinal metabolism or other mechanisms addressable in further studies.

RPE Cell and Sheet Properties in Normal and Diseased Eyes.

Previous studies of human retinal pigment epithelium (RPE) morphology found spatial differences in density: a high density of cells in the macula, decreasing peripherally. Because the RPE sheet is not perfectly regular, we anticipate that there will be differences between conditions and when and where damage is most likely to begin. The purpose of this study is to establish relationships among RPE morphometrics in age, cell location, and disease of normal human and AMD eyes that highlight irregularities reflecting damage. Cadaveric eyes from 11 normal and 3 age-related macular degeneration (AMD) human donors ranging from 29 to 82 years of age were used. Borders of RPE cells were identified with phalloidin. RPE segmentation and analysis were conducted with CellProfiler. Exploration of spatial point patterns was conducted using the "spatstat" package of R. In the normal human eye, with increasing age, cell size increased, and cells lost their regular hexagonal shape. Cell density was higher in the macula versus periphery. AMD resulted in greater variability in size and shape of the RPE cell. Spatial point analysis revealed an ordered distribution of cells in normal and high spatial disorder in AMD eyes. Morphometrics of the RPE cell readily discriminate among young vs. old and normal vs. diseased in the human eye. The normal RPE sheet is organized in a regular array of cells, but AMD exhibited strong spatial irregularity. These findings reflect on the robust recovery of the RPE sheet after wounding and the circumstances under which it cannot recover.

The Spatial Profile of Macular Pigments Is Related to the Topological Characteristics of the Foveal Avascular Zone.

PURPOSE: Macular pigments are preferentially concentrated in the central fovea, an area devoid of vasculature. We hypothesized that there may be a link between the macular pigment profile and the size and structural characteristics of the foveal avascular zone (FAZ). METHODS: Two-wavelength autofluorescence method was used to quantify macular pigment optical density (MPOD) and the radius at half peak of MPOD, which was defined as the retinal eccentricity where the MPOD value was 50% of the peak value. Volumetric spectral-domain optical coherence tomography (OCT) images of the macula were obtained from 32 subjects. The equivalent radius of the FAZ was determined using data generated from OCT angiography. Generalized estimating equations were used to test the hypothesis that there are interrelationships among the central foveal thickness, peak MPOD, the radius at half peak of MPOD and the equivalent radius of the FAZ. RESULTS: The equivalent radius of the FAZ was highly correlated with the radius at half peak of MPOD (P < .001). The equivalent radius of the FAZ was a significant predictor for central foveal thickness (P < .001). The significant predictor for peak MPOD was central foveal thickness (P = .004). Eyes with larger FAZs were more likely to have a secondary peak in their MPOD spatial profile in a zone ranging from 0.5 to 1.0 degrees from the foveal center. CONCLUSIONS: The spatial distribution of macular pigment is related to the size of the FAZ, in addition to the central foveal thickness. It is possible that xanthophyll pigment accumulation in the macula serves functions, such as attenuation of shorter wavelengths of light, that would have been provided by the light-filtering characteristics of blood vessels.

Effect of ocular magnification on macular measurements made using spectral domain optical coherence tomography.

AIM: The aim of the present study was to study the effect of ocular magnification on macular measurements made using spectral domain optical coherence tomography (OCT). MATERIALS AND METHODS: One hundred and fifty-one subjects were included from the normative study of foveal morphology carried out at our hospital. Subjects underwent comprehensive eye examination and macular scanning using Cirrus high-definition OCT and axial length (AXL) measurement. Macular cube 512 × 128 scan protocol was used for scanning the macula. Automated measurements of the fovea namely foveal diameter, foveal slope (lateral measurements) and foveal depth (axial measurement) were taken. A correction factor for ocular magnification was done using the formula t = p × q × s, where "t0" is the corrected measurement, "p" is the magnification of OCT, "q0" is the ocular magnification, and "s" is the measurement on OCT without correction. The difference between corrected and uncorrected measurements was evaluated for statistical significance. RESULTS: Mean AXL was 22.95 ± 0.78 mm. Refractive error ranged from -3D to +4D. Mean difference between measured and corrected foveal diameter, slope and depth was 166.05 ± 95.37 ΅m (P < 0.001), 0.81° ± 0.53° (P < 0.001) and 0.05 ± 0.49 ΅m (P = 0.178) respectively. AXL lesser than the OCT calibrated value of 24.46 mm showed an increased foveal diameter (r = 0.961, P < 0.001) and a reduced foveal slope (r = -0.863, P < 0.001) than the corrected value. CONCLUSION: Lateral measurements made on OCT varied with AXL s other than the OCT calibrated value of 24.46 mm. Therefore, to estimate the actual dimensions of a retinal lesion using OCT, especially lateral dimensions, we recommend correction for the ocular magnification factor.