PurposeTo 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.MethodsHigh-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.ResultsInter-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.ConclusionsWe 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.

Non-contact tests for identifying people at risk of primary angle closure glaucoma.

This is the accepted version of the paper.This version of the publication may differ from the final published version. The final publication is available at http://link.springer.com/article/10.1007/s00417-014-2915-9 2 Permanent repository link Abstract (180 words) 22Purpose: To assess the effects of incorporating individual ocular biometry 23 measures of corneal curvature, refractive error and axial length on scan 24 length obtained using Spectralis spectral domain optical coherence 25 tomography (SD-OCT). 26Methods: Two SD-OCT scans were acquired for 50 eyes of 50 healthy 27 participants, first using the Spectralis default keratometry (K) setting, then 28 incorporating individual mean-K values. Resulting scan lengths were 29 compared to predicted scan lengths produced by image simulation software 30 based on individual ocular biometry measures including axial length. 31Results: Axial length varied from 21.41 to 29.04mm. Spectralis SD-OCT scan 32 lengths obtained with default-K ranged from 5.7 to 7.3mm and with mean-K 33 5.6 to 7.6mm. We report a stronger correlation of simulated scan lengths 34 incorporating the subject's mean-K value (ρ = 0.926, P < 0.0005) compared to 35 Spectralis default settings (ρ = 0.663, P < 0.0005). 36Conclusions: Ocular magnification appears to be better accounted for when 37 individual mean-K values are incorporated into Spectralis SD-OCT scan 38 acquisition compared to using the device's default-K setting. This must be 39 considered when taking area measurements and lateral measurements 40 parallel to the retinal surface. 41 42

Central MPOD, MPODav(0-1.8), and the prevalence of atypical spatial profiles were significantly increased in South Asian compared with white subjects. Atypical profiles resulted in increased integrated MPOD up to 1.8°, and may therefore offer enhanced macular protection from harmful blue light.

PurposeMacular pigment (MP) spatial distribution varies considerably among individuals. We investigated ethnic variations in MP spatial distribution in relation to foveal architecture.MethodsWe measured MP optical density (MPOD) using heterochromatic flicker photometry (MAP test, City, University of London) in 76 white, 80 South Asian and 70 black volunteers (18 to 39 years). MPOD spatial profiles were classified objectively as exponential, ring-like or central dip, based on deviations away from an exponential fit. Measurements including total retinal thickness (RT), inner retinal layer (IRL), inner and outer plexiform layer (IPL and OPL) thickness, foveal width and foveal pit slope were taken from Spectralis SD-OCT (Heidelberg, Germany) scans.ResultsIntegrated MPOD up to 1.8° (MPODint) was higher in South Asian (0.84±0.26) and black (0.84±0.31) than whites (0.63±0.24, P<0.0005). Ethnicity explained around 10% of the variance while gender played no significant role. MPOD profile phenotypes were associated with ethnicity: 58% with ring profiles were South Asian and 43% with dip profiles were black (χ2(4,226) = 13.4, P = 0.009). MPODint was lower in exponential (0.66±0.21) compared to ring-like (0.96±0.26) and central dip (1.00±0.32, P<0.0005) groups. White subjects had thicker IRL at 0° (130±21μm) than South Asian (123±16μm) and blacks (116±14μm; F(2) = 12.4, P<0.0005), with comparable results for IPL (P<0.0005) and OPL (P = 0.03). There was no significant difference in IRL, IPL or OPL (from 0 to 3.8° retinal eccentricity) or foveal width between MP profile groups (P>0.05).ConclusionWe report a significant difference in the amount and distribution of MP between ethnicities that is not explained by variations in foveal morphology.