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Jon Barstad Gjelle, Elisabeth Bratlie Finstad, Siri Bjørnetun Jacobsen, Stuart J. Gilson, Rigmor C Baraas; Retinal shape modeled from discrete ocular length measurements, biometry and refractive error in healthy Norwegian males. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):1726.
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© ARVO (1962-2015); The Authors (2016-present)
Prolate retinal shape as formed by equatorial expansion has been suggested to be a determinant for myopia development. We investigated parameters of retinal shape through modeling of discrete ocular length (OL) measurements by partial coherence interferometry (PCI) and its correlation with spherical equivalent refraction (SER).
Twenty-three healthy males aged 21-38 years, with normal logMAR letter acuity, color vision and no observed ocular abnormalities, were included in the study. In addition to standard biometry, OLs were measured at 22 deg sagittal and transverse of the fovea in the subject’s dominant eye (Zeiss IOLMaster). SER was determined by autorefraction (Nidek AR-1000). The subject’s eye was dilated and accommodation suspended with Cyclopentolate 1% prior to examination. Vitreous depth (VD) and retinal curvature coordinates were determined from individual schematic eye models based on biometry of each subject. 3D retinal models were calculated from retinal curvature coordinates by shape fitting ellipsoids using custom software following a Nelder-Mead simplex algorithm.
Ten were emmetropes (EMM, SER: -0.50 to +0.75 D), 7 hyperopes (HYP) and 6 myopes (MYO), 92% being of Caucasian descent. Axial lengths (AL) ranged from 22.60-25.18; VD: 15.65-19.68, corneal radii (CR): 7.35-8.30 mm and SER: -4.50 - +1.92 D. MYO had significantly larger ALs than both EMM (p=0.004) and HYP (p=0.008) with larger AL/CR ratios than both EMM (p=0.008) and HYP (p<0.001). EMM and HYP showed no significant difference in AL (p=0.587), but EMM had larger AL/CR ratios than HYP (p=0.009). There was no difference in VD between refractive groups (p=0.235). The fitted models revealed an oblate retinal shape for all subjects, with vertical and horizontal asphericity significantly larger than 0 (both p≤0.001). There was no difference in horizontal or vertical asphericity between refractive groups (p=0.305 and p=0.461).
A novel 3D model of retinal shape based on discrete OLs from PCI reveal an oblate retinal shape regardless of refractive status. Furthermore, VD did not vary between refractive groups. The results indicate oblate retinal shape as formed by a global expansion, rather than prolate as formed by equatorial expansion, to be associated with myopia for the population studied here. The technique has potential as a clinical method for estimating retinal shape.
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