Does Melanin Modulate Age-Related Increase in Retinal Autofluorescence?

Abstract

Purpose:: To investigate the effect of melanin absorption on the age-related increase in autofluorescence, the autofluorescence of the retinal pigment epithelium (RPE) was examined in dog where the RPE is non pigmented in the tapetum lucidum (TL) area whereas it is pigmented in the tapetum nigrum (TN) area.

Methods:: The RPE autofluorescence was examined using "en face" observations on eye cups and classic examinations of retinal sections in two poodle dogs (3 years old and 15 years old) under UV, Blue, and Green excitation.

Results:: In "en face" images, the RPE autofluorescence was more prominent in TL area than in TN area for all excitation lights. In retinal sections, the autofluorescence was more intense in the RPE than in others layers in both TL area and TN area. The RPE autofluorescence was more intense for the older dog while pigmentation was more intense the younger dog. The location of autofluorescent spots depended on the light used for excitation, this phenomenon is more marqued in older dogs.

Conclusions:: The concentration of autofluorescent materials was constant in all RPE areas. Therefore, the difference in autofluorescence observed between the TL and TN area could be due to the concentration in melanin. Interestingly, the level of fluorescent materials increased with aging while melanin concentration appeared to decrease. Consequently both the increase in fluorescent materials and the decrease in melanin concentration may contribute to the age-related increase in RPE autofluorescence.

Keywords: retinal pigment epithelium • imaging/image analysis: non-clinical • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)