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Stephanie X. Shao, Nancy J. Coletta; Relative Thickness Of Inner And Outer Retinal Layers In Myopia As Measured With Spectral Domain Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2011;52(14):3207.
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Recent studies have used optical coherence tomography (OCT) to investigate retinal thickness in myopes, and most studies indicate that the retina is thinner in the perifoveal region in myopic eyes than in emmetropic eyes. Using time-domain OCT, Wolsley et al. (Vision Research, 2008; 48: 1554-61) reported that retinal thinning in myopia was primarily associated with thinning of the middle to inner retina. The current study examined the proportion of inner to outer retinal layer thickness, using spectral domain OCT, in a group of eyes with varying refraction.
Measurements were made on 102 eyes with a range of spherical equivalent refractive error from +1.25 D to -14.00 D, with less than 1.50 D of astigmatism. Axial lengths ranged from 21.8 mm to 30.2 mm as measured by a Zeiss IOL Master biometry system. Retinal thickness was measured with an Optovue RTVue spectral domain OCT, using the MM6 scan pattern that consists of twelve 6-mm long scans that rotate through the fovea at 15° intervals. Retinal thickness was analyzed for the central 1 mm, parafovea (1-3 mm diameter ring) and perifovea (3-6 mm diameter ring). The RTVue software segments the retinal layers at the inner plexiform layer (IPL) into outer retina, from retinal pigment epithelium (RPE) to IPL, and inner retina, from IPL to inner limiting membrane (ILM).
Full retinal thickness significantly decreased with increasing myopia and axial length in both the parafoveal (p<0.002) and perifoveal (p<0.0001) rings. The thickness of the central 1 mm region increased significantly with myopia (p=0.009) and also increased with axial length but not significantly (p=0.23). The proportion of the inner retinal thickness to the outer retinal thickness decreased with increasing myopia in both the parafoveal (r=0.195;p=0.049) and perifoveal (r=0.282;p=0.004) rings. Similarly the inner/outer retinal thickness proportion decreased with increasing axial length in both parafoveal and perifoveal regions although this effect was significant only in the perifoveal ring (r=0.28;p=0.004). The inner/outer retinal thickness ratio did not vary significantly with either refraction or axial length over the central 1 mm region.
Myopic eyes exhibit relatively more thinning of the inner retinal layers in the parafoveal and perifoveal regions, which correspond to angular eccentricities of about 1.7 to 10 deg from the fovea. These results are consistent with those of Wolsley et al. who showed selective thinning of the inner retina in myopes at slightly larger retinal eccentricities.
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