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- Title
COMPENSATORY CHANGES IN RETINA FUNCTION DURING EARLY STAGES OF AGE-RELATED MACULAR DEGENERATION.
- Authors
Johnson, Antonia; Freund, Paul; Garcha, Jaspreet; Sauvé, Yves
- Abstract
Age-related macular degeneration (AMD) is the leading cause of blindness in the elderly of the Western world. One in four Canadians over 75 years of age has AMD. In order to find a cure for AMD it is essential to consider the baseline age-related retinal changes on top of which pathophysiological events take place. We undertook a detailed study of retina function (using the electroretinogram, ERG) in five subjects (76±10y) afflicted by the early (dry) and late (wet) forms of AMD in either eye. Results were compared between both eyes and with healthy eyes of subjects from three age groups: 20-39y (n=27; mean age 25±5y), 40-59y (n=20; mean age 53±5y), and 60y+ (n=18; mean age 68±5y). Changes in ERG properties were found in the oldest group when compared to the two younger groups: 1) a less pronounced photopic hill, reflecting changes in the OFF-bipolar system; 2) the slowing of implicit times, suggesting the occurrence of biochemical changes in rod and cone photoreceptors; 3) the selective amplitude reduction of maximal dark-adapted a-wave (reduced rod activity) and not b-wave (maintained post-synaptic activity from rod ON-bipolar cells) could be linked to post-synaptic compensation. Recordings from early AMD eyes showed an exacerbation of the changes seen in age-matched subjects with healthy eyes: 1) lack of any hill effect; 2) severely delayed responses; 3) further reductions in a-wave amplitudes (indicative of more pronounced photoreceptor dysfunction) while b-wave amplitudes were still unchanged, pointing to the occurrence of post-synaptic compensation despite pathological photoreceptor dysfunction. In contrast, late AMD eyes lacked any signs of such compensatory changes: there was a generalized loss of responsiveness in all ERG components (decreased amplitudes and delayed responses for all ERG components).
- Subjects
AGE factors in retinal degeneration; BLINDNESS; RETINAL diseases; DEGENERATION (Pathology); EYE diseases
- Publication
UBC Medical Journal, 2011, Vol 2, Issue 2, p9
- ISSN
1920-7425
- Publication type
Abstract