Predicting Visual Acuity Loss In An Older Population: The Ski Study

Abstract: : Purpose: To evaluate which if any vision function measures predict future loss of high contrast visual acuity in an aging population. Methods: A battery of vision tests was performed binocularly on 596 randomly selected community living older individuals at two points in time separated by 4.4 years on average. The mean age at the second visit was 78.2 years (s.d. 8 yrs; range 64-104 yrs). The test battery included high and low contrast acuity (Bailey-Lovie Charts), contrast sensitivity (Pelli-Robson chart), low luminance low contrast acuity (SKILL Card), low contrast acuity in the presence of disability glare (Berkeley Glare Test), stereopsis (Frisby test), color vision (D-15), temporal vision (sensitivity to 4, 17 Hz and CFF), glare recovery, standard and attentional visual fields, and reading performance. Logistic regression analysis was used to determine which, if any, of the other vision measures could predict significant future loss of standard high contrast visual acuity (doubling of acuity threshold per decade) in those people who had 20/40 or better acuity at the first visit (90% of the group). Results: Several spatial vision measures were statistically significant predictors of future high contrast visual acuity loss. A deficit of 0.3 log units at the first visit in low contrast acuity in disability glare, low luminance low contrast acuity (SKILL dark acuity), or contrast sensitivity each increased the risk of subsequent visual acuity loss by about a factor of 2. In addition, reduced stereoacuity increased the risk of future visual acuity loss by a factor of 1.45. Individuals with both a spatial vision deficit (disability glare, SKILL dark acuity, or contrast sensitivity) and reduced stereoacuity were 2.5 times more likely than individuals without deficits to lose acuity. Low contrast distance acuity was not a significant predictor. Neither was glare recovery, temporal vision nor any aspect of the visual fields. Age per se was not a significant predictor of future acuity loss. Conclusion: Older people with normal or near normal standard visual acuity who have abnormalities in glare disability or SKILL dark acuity or contrast sensitivity and stereopsis are much more likely to subsequently lose high contrast acuity than those without defecits in these measures. These findings highlight the importance of measures of vision function other than standard acuity. These other measures, which are more sensitive to subtle alterations in the visual system, may help provide warning of the future development of sight-threatening conditions.