The most common test for vision loss from glaucoma is standard automated perimetry (SAP). For the test, patients are asked to look into a specific instrument and indicate when they detect a small light or shimmer appearing at selected locations in their vision field. The test requires the patient’s concentration. A 2017 report in JAMA Ophthalmology found that mild cognitive decline associated with aging can impair the ability of individuals to perform the test-and compromise the reliability of the results.
The study involved 115 patients (average age, 67) who either had glaucoma or early warning signs of the disease. Over the course of several years, their vision was tested periodically using SAP, and they were given a standard psychological test for cognitive impairment. At the start of the study, very few patients had evidence of mild cognitive impairment. But over the roughly 2.5 years they were followed, a growing percentage showed signs of cognitive loss. And cognitive impairment, the researchers found, was associated with greater variability in visual field results-an indication that those results were less reliable.
The study is important because mild cognitive impairment is increasingly common after people reach their mid-60s, a time when glaucoma also becomes more common. The researchers suggest that ophthalmologists may need to consider testing for cognitive impairment in order to be alerted when results of visual field testing may not be as reliable.