Glaucoma changes rapid contrast adaptation

Glaucoma, but not ageing, changes rapid contrast adaptation, which is vital to visual processing in natural visual environments, say researchers from Australia in a recent study. "Our results imply that glaucoma produces abnormalities in natural visual experiences in central vision," they write.

Their study included 14 people with glaucoma, 17 age-similar controls, and 19 younger adults. The investigators measured contrast detection and discrimination thresholds in central vision for briefly presented Gabor patches with and without adaptation to 50% contrast Gabor patches. They measured detection thresholds at 47, 106, 200, 400, 600 and 1000 msecs adaptation, and they measured discrimination thresholds after adaptation relative to a reference contrast below, equivalent to, or above the adaptor.

The unadapted detection and discrimination thresholds were elevated in those in the glaucoma group compared with the age-similar controls, the authors found. Ageing elevated unadapted thresholds in normal observers. At 47 msecs after adaptation, those in the glaucoma group experienced reduced effects of adaptation relative to those in the control group. Adaptation was also reduced when the reference contrast was equivalent to the adaptor. Ageing, however, did not change adaptation in normal observers.

To read an abstract of the study, visit the journal

Investigative Ophthalmology and Visual Science

.