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The sclera plays an important role in the biomechanical stability of the eye. We aimed to examine if changes in the shape of the anterior sclera occur in response to accommodation and convergence. Methods: Thirty-six healthy young adult participants aged between 18 and 30 years including 18 myopes (-0.5 to -4.0 D) and 18 emmetropes (+0.5 to -0.25 D) were recruited. Eye surface profilometry was used to evaluate the anterior eye surface shape before and during visual tasks involving accommodation (5.0 D demand), simulated convergence (9°demand) and their combination. The changes in the sagittal height and axial radius of curvature of the nasal (n = 25) and temporal (n = 31) corneal periphery and anterior sclera were analysed in those participants with complete and reliable data on these sides. Results: Significant changes were confined to the nasal anterior scleral surface. A significant forward movement of the surface accompanied accommodation (mean change: 5 AE 2 µm), convergence (19 AE 6 µm), and their combination (16 AE 6 µm). There was flattening with convergence (0.092 AE 0.044 mm) and with the combination of accommodation and convergence (0.201 AE 0.071 mm). The changes in response to accommodation and convergence increased peripherally. Changes were not significantly different between low to moderate myopes and emmetropes. Conclusions: Accommodation and simulated convergence affect the nasal anterior scleral shape, with the greatest changes associated with convergence and being most evident in the more peripheral nasal scleral regions.

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Purpose Changes in retinal thickness are common in various ocular diseases. Transverse magnification due to differing ocular biometrics, in particular axial length, affects measurement of retinal thickness in different regions. This study evaluated the effect of axial length and refractive error on measured macular thickness in two community-based cohorts of healthy young adults. Methods A total of 2160 eyes of 1247 community-based participants (18–30 years; 23.4% myopes, mean axial length = 23.6mm) were included in this analysis. Macular thickness measurements were obtained using a spectral-domain optical coherence tomography (which assumes an axial length of 24.385mm). Using a custom program, retinal thickness data were extracted at the 9 Early Treatment of Diabetic Retinopathy Study (ETDRS) regions with and without correction for transverse magnificent effects, with the corrected measurements adjusting according to the participant’s axial length. Linear mixed models were used to analyse the effect of correction and its interaction with axial length or refractive group on retinal thickness. Results The raw measures (uncorrected for axial length) underestimated the true retinal thickness at the central macula, while overestimating at most non-central macular regions. There was an axial length by correction interaction effect in all but the nasal regions (all p<0.05). For each 1mm increase in axial length, the central macular thickness is overestimated by 2.7–2.9μm while thicknesses at other regions were underestimated by 0.2–4.1μm. Based on the raw thickness measurements, myopes have thinner retinas than non-myopes at most non-central macular. However, this difference was no longer significant when the corrected data was used. Conclusion In a community-based sample, the raw measurements underestimate the retinal thickness at the central macula and overestimate the retinal thickness at non-central regions of the ETDRS grid. The effect of axial length and refractive error on retinal thickness is reduced after correcting for transverse magnification effects resulting from axial length differences.