Ageing changes in retinal outer nuclear layer thickness and cone photoreceptor density using adaptive optics-free imaging

Purpose: To investigate age-related changes of the outer nuclear layer (ONL) thickness and cone density, and their associations in healthy participants using a modified, narrow scan-angle Heidelberg Retina Angiograph (HRA2). Methods: Retinal cones were imaged outside the fovea at 8.8 degrees eccentricity and cone density was compared to ONL thickness measurements obtained by Spectral-Domain Optical Coherence Tomography (SD-OCT) at the same locations. Fifty-six eyes of 56 healthy participants with a median age (interquartile range, IQR) of 37 years (29-55) were included. Results: Median (IQR) cone count was 7,472 (7,188, 7,746) cones/mm(2) and median (IQR) ONL thickness was 56 (52, 60) mu m for healthy participants. Both cone density and ONL thickness were negatively associated with age: cone density, R-2 = 0.16 (F(1,54) = 10.41, P = 0.002); ONL thickness, R-2 = 0.12 (F(1,54) = 7.41, P = 0.009). No significant association was seen between cone density and ONL thickness (R-2 = 0.03; F(1,54) = 1.66, P = 0.20). Conclusion: Cone density was lower, and ONL thinner, in older compared to younger participants, therefore, image-based structural measures should be compared to age-related data. However, cone density and ONL thickness were not strongly associated, indicating that determinants of ONL thickness measurements other than cone density measurements, and including measurement error, have a major influence.

Automated summary

This study investigated the age-related changes of outer nuclear layer (ONL) thickness and cone density in healthy participants using a modified narrow scan-angle Heidelberg Retina Angiograph (HRA2). The results showed that both cone density and ONL thickness decreased with age. However, there was no strong correlation between cone density and ONL thickness, suggesting that factors other than cone density contribute to ONL thickness measurements.