Outer Retinal Layers’ Thickness Changes in relation to Age and Choroidal Thickness in Normal Eyes

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 (&gt;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: <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M1"><mml:mrow><mml:mi>P</mml:mi><mml:mo>&lt;</mml:mo><mml:mn>0.001</mml:mn></mml:mrow></mml:math>). Moreover, the 3 groups were significantly different from each other regarding the CT (central: <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M2"><mml:mrow><mml:mi>P</mml:mi><mml:mo>&lt;</mml:mo><mml:mn>0.001</mml:mn></mml:mrow></mml:math>); 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, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M3"><mml:mrow><mml:mi>P</mml:mi><mml:mo>&lt;</mml:mo><mml:mn>0.001</mml:mn></mml:mrow></mml:math>, and central CT: r = −0.725, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M4"><mml:mrow><mml:mi>P</mml:mi><mml:mo>&lt;</mml:mo><mml:mn>0.001</mml:mn></mml:mrow></mml:math>) while ONL-IS showed statistically nonsignificant correlation with age (central ONL-IS: r = −0.08, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M5"><mml:mrow><mml:mi>P</mml:mi><mml:mo>=</mml:mo><mml:mn>0.376</mml:mn></mml:mrow></mml:math>). Multiple regression analysis revealed that the most important determinant of central 1 mm RPE-OS thickness in this study was age ( β = −0.087, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M6"><mml:mrow><mml:mi>P</mml:mi><mml:mo>=</mml:mo><mml:mn>0.010</mml:mn></mml:mrow></mml:math>) rather than choroidal thinning ( β = 0.001, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M7"><mml:mrow><mml:mi>P</mml:mi><mml:mo>=</mml:mo><mml:mn>0.879</mml:mn></mml:mrow></mml:math>). 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.