The Distribution of the Photoreceptor Outer Segment Length in a Healthy Population

Abstract

Purpose . To evaluate the effects of age and sex on the photoreceptor outer segment (PROS) length in healthy eyes, using spectral-domain optical coherence tomography (SD-OCT). Methods . A total of 97 eyes of 97 healthy participants (spherical equivalent &lt; ±1 diopters [D]) were scanned with SD-OCT. The patients were divided into 3 groups by age: group 1 (0–20 years), group 2 (21–40 years), and group 3 (41–60 years). The PROS length was defined as the distance from the inner surface of IS/OS (inner segment/outer segment) band to the inner surface of retinal pigment epithelium (RPE). Results . The mean PROS length was 52.01 ± 3.79 μ m in females and 53.41 ± 3.37 μ m in males (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M1"><mml:mi>p</mml:mi><mml:mo>=</mml:mo><mml:mn>0.061</mml:mn></mml:math>). The mean PROS length of the different groups was 53.70 ± 3.18 μ m (0–20 years), 52.14 ± 3.64 μ m (21–40 years), and 52.20 ± 3.95 μ m (41–60 years) (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M2"><mml:mi>p</mml:mi><mml:mo>=</mml:mo><mml:mn>0.155</mml:mn></mml:math>; ANOVA test). Multiple linear regression analysis revealed a −0.039 μ m decline in PROS length per year (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M3"><mml:mi>p</mml:mi><mml:mo>=</mml:mo><mml:mn>0.074</mml:mn></mml:math>) and a −1.408 μ m decline in females (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M4"><mml:mi>p</mml:mi><mml:mo>=</mml:mo><mml:mn>0.055</mml:mn></mml:math>). Conclusion . The difference in PROS length was not statistically significant neither for age nor for gender; females tended to have a lower PROS length than males, and PROS length was slightly higher in the first two decades of life.