Foveal cone-photoreceptor integrity in aging macula disorder

¹ Department of Ophthalmology, UMC Utrecht, AZU E03.136, Utrecht, Netherlands
² Department of Ophthalmology, University Eye Clinic Maastricht, Maastricht, Netherlands
³ Department of Ophthalmology, UMC Utrecht, AZU E03.136, PO Box 85500, Utrecht, NL-3508 GA, Netherlands

^* To whom correspondence should be addressed. E-mail: M.J.Kanis{at}umcutrecht.nl.

	Abstract

Purpose: To establish the relation between AMD stage and a quantitative measure for the integrity of foveal cone photoreceptors related to the optical Stiles-Crawford effect. Methods: Fifty-six AMD eyes and 57 control eyes were included in the final analysis. AMD was graded conform the International Classification System into 5 mutually exclusive stages. Stages 0-1 were labeled no AMD, stages 2-3 were called early AMD, and stage 4 was called late AMD. Fundus reflectometry, together with a model fit procedure, provided information on directional cone reflectance (Rd), a quantitative measure for the integrity of foveal cone photoreceptors. Optical densities of macular pigment (MPOD) and melanin (MOD) were also obtained. A general linear model analysis was used to compare Rd, MPOD and MOD between AMD stages. Results: Mean Rd was lower in early AMD (0.92%, P < 0.001) and late AMD (0.86%, P < 0.001) compared to mean Rd in the no AMD stage (1.76%). Mean MPOD was not different in early AMD (0.53, P = 0.05), but it was lower in late AMD (0.19, P < 0.001) compared to mean MPOD in the no AMD stage (0.42). Mean MOD was lower in early AMD (1.09, P = 0.001) and late AMD (1.01, P = 0.004) compared to mean MOD in the no AMD stage (1.23). Conclusions: Foveal cones show signs of misalignment and/or outer segment deterioration in early AMD. Melanin rather than macular pigment might play a protective role against AMD, although loss of these ocular pigments can also be caused by AMD.

Key Words: AMD, cones, antioxidants, melanin, reflectometry, macular pigment