Inter-relationship of Retinal, Choroidal, and Scleral Thickness in High Myopia
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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 ≤-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 ± SD axial length was 30.17 ± 2.23 mm, sub-foveal retinal thickness was 245 ± 28 µm, sub-foveal choroidal thickness was 82 ± 46 µm, and sub-foveal scleral thickness was 254 ± 68 µm. 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 µm) and scleral thickness (decreased by 4.31 µm, p≥0.05), but sub-foveal choroidal thickness decreased by 10.35 µm (p=0.02). For a 1D decrease in spherical equivalent refraction, the choroidal thickness reduced significantly (decreased by 5.88 µm, p<0.001), while there was no significant variation in retinal (decreased by 0.68 µm, p=0.55) and scleral thickness (increased by 0.13 µm, p=0.98). The association of the sub-foveal retinal, choroidal, and scleral thickness was weak and was not significant in high myopes (p≥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.
