Abnormal color vision increases significantly with aging and affects half or more people 70 and older, according to a new study by researchers at the Smith-Kettlewell Eye Research Institute in San Francisco and the University of California at Berkeley.

The study authors gave color vision tests to 865 randomly chosen adults ages 58 to 102 years, excluding anyone with diagnosed “color blindness. The researchers found that 40 percent of the study participants had abnormal results on one of the two color vision tests used in the study, twenty percent failed both tests and the failure rate was significantly higher in older age groups. “These individuals would have problems carrying out some tasks that rely on color vision,” said lead researcher Marilyn E. Schneck, Ph.D., a research scientist in the Vision Sciences Program at UC/Berkeley’s School of Optometry.

Tasks that rely on color vision can include distinguishing among pill colors, finding a car in a parking lot and even matching clothes colors. Mismatched clothes could give the impression of a cognitive disability rather than a vision one.

While color-vision abnormalities were uncommon in people younger than 70, they were present in about 45 percent of people in their mid-70s, up to 50 percent of those 85 and older, and nearly two-thirds of those in their mid-90s.

Nearly 80 percent of the abnormalities involved confusion of lighter shades of blue versus purple and yellow versus green and yellow-green. The researchers say that the new results confirm previous studies showing that color vision deteriorates measurably with aging and that most subtle aging-related color vision abnormalities are likely to go unnoticed if testing isn’t done. Factors that may contribute to changes in color vision with aging, and to blue-yellow recognition especially include reduced pupil size which lets less light into the eye, increased yellowing of the lens inside the eye, increased rates of eye diseases and changes in the sensitivity of the vision pathways.

The study was published in Optometry and Vision Science, the Journal of the American Academy of Optometry.