visual impairment

Older news items (pre-2010) brought over from the old website

Age-related eye disease associated with cognitive impairment

Age-related macular degeneration (AMD) is the leading cause of visual impairment in industrialized nations, and like Alzheimer's disease, involves the buildup of beta-amyloid peptides in the brain, as well as sharing similar vascular risk factors. A study of over 2000 older adults (69-97) has revealed an association between early-stage AMD and cognitive impairment, as assessed by the Digit Symbol Substitution Test (a test of attention and processing speed). There was no association with performance on the Modified Mini-Mental State Examination (used to assess dementia).
It’s worth noting that in the same journal two studies into the association between dietary fat intake and AMD appeared. The first, four-year, study involved over 6700 older adults and found that higher trans-unsaturated fat intake was associated with a higher incidence of AMD, while higher omega-3 fatty acid and higher olive oil intake were each associated with a lower incidence. The second, ten-year, study involving nearly 2500 older adults, found regular consumption of fish, greater intake of omega-3 fatty acids, and low intake of linoleic acid (perhaps because a higher intake implies a lower intake of omega-3 oils? linoleic acid is an omega-6 fatty acid), were all associated with a lower incidence of AMD. Fish and omega-3 oils have of course been similarly associated with lower rates of dementia and age-related cognitive impairment.

http://www.eurekalert.org/pub_releases/2009-05/jaaj-aed050709.php

Age-related vision problems may be associated with cognitive impairment

Age-related macular degeneration (AMD) develops when the macula, the portion of the eye that allows people to see in detail, deteriorates. An investigation into the relationship between vision problems and cognitive impairment in 2,946 patients has been carried out by The Age-Related Eye Disease Study (AREDS) Research Group. Tests were carried out every year for four years. Those who had more severe AMD had poorer average scores on cognitive tests, an association that remained even after researchers considered other factors, including age, sex, race, education, smoking, diabetes, use of cholesterol-lowering medications and high blood pressure. Average scores also decreased as vision decreased. It’s possible that there is a biological reason for the association; it is also possible that visual impairment reduces a person’s capacity to develop and maintain relationships and to participate in stimulating activities.

Chaves, P.H.M. et al. 2006. Association Between Mild Age-Related Eye Disease Study Research Group. 2006. Cognitive Impairment in the Age-Related Eye Disease Study: AREDS Report No. 16. Archives of Ophthalmology,124, 537-543.

http://www.eurekalert.org/pub_releases/2006-04/jaaj-avp040606.php

The reorganization of the visual cortex in congenitally blind people

Studies indicate that congenitally blind people have superior verbal memory abilities than the sighted. A new study helps us understand why this is so. Some 25% of the human brain is devoted to vision. Until now it was assumed that loss of vision rendered these regions useless. Now it appears that in those blind from birth, the part of the occipital cortex usually involved in vision is utilized for other purposes. Extensive regions in the occipital cortex, in particular the primary visual cortex, are activated not only during Braille reading, but also during performances of verbal memory tasks, such as recalling a list of abstract words. No such activation was found in a sighted control group. It also appears that the greater the occipital activation, the higher the scores in the verbal memory tests.

http://www.eurekalert.org/pub_releases/2003-06/huoj-hur061703.php