Inter-relationship of Retinal, Choroidal, and Scleral Thickness in High Myopia

Purpose Considering that myopia is associated with thinning of the ocular coats, this study investigated the inter-relationship of retinal, choroidal and scleral thickness in foveal regions in Indian high myopes. Methods A total of 23 high myopes (spherical equivalent refraction [&le;]-6.00D) aged 16 to 35 years underwent posterior segment imaging with swept-source optical coherence tomography. The retinal, choroidal and scleral thickness was determined using semi-automated custom-designed software at sub-foveal regions. Axial length was determined using Lenstar LS 900 non-contact biometer. Results The mean plus-or-minus sign SD axial length was 30.17 plus-or-minus sign 2.23 mm, sub-foveal retinal thickness was 245 plus-or-minus sign 28 lower case Greek mum, sub-foveal choroidal thickness was 82 plus-or-minus sign 46 lower case Greek mum, and sub-foveal scleral thickness was 254 plus-or-minus sign 68 lower case Greek mum. The choroid was significantly thinner compared to the retina and sclera (p<0.001). With a 1 mm increase in axial length, there was no significant variation in sub-foveal retinal (increased by 0.86 lower case Greek mum) and scleral thickness (decreased by 4.31 lower case Greek mum, p[&ge;]0.05), but sub-foveal choroidal thickness decreased by 10.35 lower case Greek mum (p=0.02). For a 1D decrease in spherical equivalent refraction, the choroidal thickness reduced significantly (decreased by 5.88 lower case Greek mum, p<0.001), while there was no significant variation in retinal (decreased by 0.68 lower case Greek mum, p=0.55) and scleral thickness (increased by 0.13 mum, p=0.98). The association of the sub-foveal retinal, choroidal, and scleral thickness was weak and was not significant in high myopes (p[&ge;]0.10). Conclusions With increasing axial length and severity of myopia in high myopes, compared to scleral and retinal thickness, the choroidal thickness alone decreased significantly. Our findings indicate that the changes in the choroid do not necessarily reflect the changes in retinal and scleral thickness and highlight the importance of the choroid as a marker for axial elongation even in high myopes.