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S. Dubuc, J. E. S. Gomolin, O. Kasner, O. Overbury; Comparing Performance on Cognitive Screening Tests: Individuals With Age-related Macular Degeneration, Glaucoma and Age-matched Controls. Invest. Ophthalmol. Vis. Sci. 2009;50(13):735.
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Anatomical studies have shown that the cellular losses and dysfunctions seen in Alzheimer's Disease (AD) demonstrate a similar pathogenesis to the cellular loses and dysfunctions which occur in the presence of retinal diseases, such as Age-related Macular Degeneration (AMD) or glaucoma. Furthermore, a number of studies have recently demonstrated co-morbidity between retinal diseases and pathological cognitive impairment, above what would be expected by chance. However, this co-morbidity with cognitive loss has only been found among individuals with relatively severe vision loss due to AMD and glaucoma. Most often, cognitive testing consists of a modified version of the Mini-Mental State Exam (MMSE), a short screening tool. Recently the MoCA (Montreal Cognitive Assessment) has been developed as an alternative to the MMSE. Although highly correlated with the MMSE, the MoCA may be a more sensitive tool for detecting Mild Cognitive Impairment (MCI), which may precede AD. Both tests are scored out of a possible 30 points and have the same cut-off of 26, a score below this being suggestive of a cognitive impairment. In the present study, the MMSE and the MoCA were compared among individuals with early atrophic AMD, glaucoma and no visual pathology.
Number of participants in each group and their respective mean ETDRS acuities OU were: 17 with AMD (20/27), 19 with glaucoma (20/36) and 16 visually healthy people (20/23). Participants ranged in age between 47 and 89, with a mean of 72 years. The MMSE and the MoCA were administered in random order to all participants.
Chi Square analysis indicated a significantly higher proportion of individuals scoring below the cut-off point of 26 for possible cognitive impairment on the MoCA, chi squared (2) = 32.52 p<.001.
Given the results of our chi-squared analysis, the MoCA (but not the MMSE) may be detecting the presence of subtle cognitive changes in a population with early progressive retinal disease. Given the suggested co-morbidity between retinal diseases and cognitive impairment, this study may add weight to the possibility that age-related visual disorders and MCI/eventual AD share a common pathogenesis.
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