Abstract
Purpose To identify and correlate age-related changes in outer retinal layers' thickness and choroidal thickness (CT) in the normal eyes using spectral-domain optical coherence tomography (SD-OCT) and to investigate factors affecting these changes. Study Design Observational cross-sectional study. Subjects and Methods We studied 125 healthy Egyptians between 20 and 79 years old. Patients were divided into 3 groups: group 1 (20–40 years), group 2 (40–60 years), and group 3 (>60 years). All patients had full ophthalmic examination. SD-OCT was done to measure the 9 ETDRS macular grid sectors of retinal pigment epithelium and photoreceptor outer segment (RPE-OS), outer nuclear layer and photoreceptor inner segment (ONL-IS), and choroidal thickness (CT) (by enhanced depth imaging). Results RPE-OS was significantly thinner in group 3 than in the other 2 groups (central: P < 0.001). Moreover, the 3 groups were significantly different from each other regarding the CT (central: P < 0.001); significant thinning was noticed in the choroid with age. The 3 groups did not show significant difference concerning the ONL-IS thickness. RPE-OS and CT showed statistically significant negative correlation with age (central RPE-OS: r = −0 C.345, P < 0.001, and central CT: r = −0.725, P < 0.001) while ONL-IS showed statistically nonsignificant correlation with age (central ONL-IS: r = −0.08, P=0.376). Multiple regression analysis revealed that the most important determinant of central 1 mm RPE-OS thickness in this study was age (β = −0.087, P=0.010) rather than choroidal thinning (β = 0.001, P=0.879). Conclusion RPE-OS layer thickness shows significant thinning with increasing age, and with decrease in CT, however, age is the most determinant factor of this thinning.
Highlights
Is allows precise segmentation of individual retinal layers and provides thickness maps that could help in studying diseases affecting specific retinal layers [3]
Previous studies using ultrahigh resolution optical coherence tomography (OCT) showed that the severity of photoreceptor loss is associated with visual loss in retinitis pigmentosa, [13] while other studies using spectral-domain optical coherence tomography (SD-OCT) showed that by measuring the thickness of the outer nuclear layer in the fovea, we can predict visual prognosis in retinal diseases such as central serous chorioretinopathy [16], polypoidal choroidal vasculopathy [17], and epiretinal membrane [15]
Earlier studies using standard deviation (SD)-OCT [18,19,20,21] in healthy eyes reported changes in the macular profile in relation to factors such as age, sex, and axial length [15]. ickness of different retinal layers has shown variation according to age in variable studies as well [8, 14, 21, 22]
Summary
Outer Retinal Layers’ Thickness Changes in relation to Age and Choroidal Thickness in Normal Eyes. Many studies have proved significant choroidal thinning with age [5, 9, 10], which could be of great importance since the outer retinal layers do not have a vascular network and rely on choriocapillaris, which exhibits a slow blood velocity, in supplying the retinal pigment epithelium (RPE) and outer retina with oxygen and nutrients, maintaining normal retinal function [11, 12]. Variation in outer retinal layers’ thickness with age could be either due to vascular insufficiency as a result of choroidal thickness change or direct effect due to the aging process itself [6]
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