Reduced zinc and copper in the retinal pigment epithelium and choroid in age-related macular degeneration

Abstract

Purpose: To measure zinc and copper levels in the retinal pigment epithelium (RPE) and choroid complex and in the neural retina in subjects with and without age-related macular degeneration (AMD).

Design: Laboratory investigation.

Methods: Eighty-eight donor eyes (44 subjects) were analyzed. After retinal dissection, the RPE and choroid complex was photographed. Using the Minnesota Grading System (MGS), the RPE and choroid complex was classified into 1 of 4 stages as defined by the Age-Related Eye Disease Study. Subjects without AMD were defined as both eyes having MGS stage 1; subjects with AMD were defined as both eyes having MGS stages 2 through 4. Zinc and copper levels were determined by using an inductively coupled plasma-mass spectrometer. Metal levels from two eyes of the same subject were averaged and treated as one observation. Differences in metal levels were examined by using Wilcoxon rank-sum tests.

Results: The mean RPE and choroid complex zinc level in subjects with AMD (+/- standard deviation, 223.7 +/- 94.0 microg/g; n = 15) was reduced 24% when compared with that of subjects without AMD (292.1 +/- 98.5 microg/g; n = 29; P = .01). The mean RPE and choroid complex copper level in subjects with AMD (5.1 +/- 1.1 microg/g) was reduced 23% when compared with that of subjects without AMD (6.6 +/- 1.4 microg/g; P = .002). No difference was detected in retinal zinc and copper levels in subjects with and without AMD (P > .09).

Conclusions: Reduced RPE and choroid complex zinc and copper levels in AMD eyes combined with previous information that oral supplementation of zinc plus copper reduces the risk of progression of AMD suggests that metal homeostasis plays a role in AMD and in retinal health.