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

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).

A total of 97 eyes of 97 healthy participants (spherical equivalent < ±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).

The mean PROS length was 52.01 ± 3.79 μm in females and 53.41 ± 3.37 μm in males (p = 0.061). The mean PROS length of the different groups was 53.70 ± 3.18 μm (0-20 years), 52.14 ± 3.64 μm (21-40 years), and 52.20 ± 3.95 μm (41-60 years) (p = 0.155; ANOVA test). Multiple linear regression analysis revealed a -0.039 μm decline in PROS length per year (p = 0.074) and a -1.408 μm decline in females (p = 0.055).

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.