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I. Cunningham, P.C. Knox, F.J. Rowe, A.C. Fisher; Aging and Modified Visual Fields: Effects of Task Difficulty . Invest. Ophthalmol. Vis. Sci. 2003;44(13):1954.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Age related visual decline tends to be underestimated by current clinical tests. We modified an automated perimeter by adding a second task at fixation and investigated visual fields in conditions of focused (FA) and divided attention (DA). Performance was observed between groups of young and older subjects. Methods: Two lasers projected red targets 2mm either side of the standard fixation target in a Humphrey Field Analyzer. 15 young (mean age 20±1.5y, range: 18-23) and 16 older subjects (72±5y, 65-80) were assessed under FA using Fastpac 30-2 program (FA1). Subjects then repeated the test twice under DA by responding with a second handheld button to asynchronously presented central laser targets (DA1a,b). Subjects also repeated the DA test, only responding when the central target appeared to right of fixation (DA2) before another FA assessment (FA2). Results: For young subjects there was no significant difference in thresholds between FA and DA conditions. There were small but insignificant differences for older subjects from the macular to 20° region. In the 20 to 30° region, threshold increased by 5.61cd/m2, p<0.05 (DA1a) and 3.79cd/m2, p=0.27 (DA1b) compared with FA1. When required to discriminate between left and right targets, thresholds increased significantly in old subjects (DA2: 5.15cd/m2, p=0.03 compared with FA2). An insignificant improvement was noted between the two FA field tests (young: 0.73cd/m2; old: 0.87cd/m2). Mean reaction time for the fixation task alone was comparable (young: 370 ±58ms vs. old: 363±73ms, p>0.05). However when combined with the threshold task reaction times increased by much more in the older group (DA1a: 499±58ms vs. 567±66ms, p<0.0001; DA1b: 496±63msec vs. 574±81msec, p<0.0001). When task difficulty increased reaction time increased in the younger group. There was no effect on reaction time in the older group. The difference between the groups remained statistically significant. (545±46ms vs. 572±77ms, p<0.0001). Conclusion: Visual fields for young subjects are not compromised when combined with central detection tasks. In older subjects visual fields are reduced and reaction times to targets at fixation increased in DA conditions, dependant on task difficulty. These modified responses may be more representative of visual function during normal behaviour.
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