Binocular vision in older people with adventitious visual impairment: sometimes one eye is better than two

To determine the effect of adventitious visual impairment (low vision) on monocular and binocular spatial contrast sensitivity of older people.

A between-within repeated measures design.

Fifty-nine older adults between the ages of 50 and 96; 49 of the observers had age-related macular degeneration (AMD).

Visual acuity screening and spatial contrast sensitivity.

In almost half of the population with AMD, the sensitivity to spatial information, as measured by spatial contrast sensitivity, is worse when both eyes are used than when the stimuli are viewed with only one eye. This "binocular inhibition" is not related to the contrast sensitivity of the better eye or to acuities. Furthermore, this inhibition process is reflected primarily in images with medium to low spatial frequency components (medium to large size bars).

These results have important implications for understanding the functional impact of low vision in older people. They suggest that almost one-half of older people with AMD view the world best using only one of their eyes, whereas for the other half, there is an advantage to using binocular vision for certain visual tasks.