Demystifying science | Does eye color affect sight?

Each week, our journalist answers scientific questions from readers.

No, but there are subtle differences in vision depending on eye color.

The pupil of brown irises has greater contractility – that is, a greater ability to contract to change the amount of light that reaches the retina – than that of green and blue eyes, explains Philippe Valmaggia, of the University of Basel, Switzerland, which published a study on the subject last November in the journal Translational Vision Science and Technology. “We have not yet measured what clinical impact this had. »

Marie-Claude Robert, ophthalmologist at the CHUM, confirms that people with blue eyes are more easily dazzled than those with brown eyes. “This is probably the cause of the difference in contractility observed in the study,” says Dr.^D Robert.

She cautions, however, that the differences are small compared to natural variations in the population, and that the journal where the Swiss study was published has a low “impact factor”, a measure of the quality of a scientific journal.

The study of D^r Valmaggia was made on 71 healthy patients.

Scientific studies on the clinical effects of eye color are not commonplace. A Texas study, published in 2010 in the Journal of Ocular Pharmacology and Therapeutics, concluded that eye color does not affect the ability to see in dim light. An Australian study, published in 2000 in theAmerican Journal of Ophthalmology, asserted that blue eyes increased the risk of cataracts by 60%. And an Austrian study, published in 2012 in the journal Graefe’s Archive for Clinical and Experimental Ophthalmologyconcluded that people with brown eyes were 14% less likely to experience pathological glare, but had no better acuity than people with blue eyes.

Macular degeneration is the only disorder for which there is a demonstrated link to eye color, according to Dr.^D Robert.

“Women and farsighted people also have a slightly higher risk,” says the ophthalmologist.

The D^D Robert considers this to be a delicate subject. “I sometimes see patients who have tried or are considering surgery to change the color of their eyes,” says Dr.^D Robert. These are not safe interventions. It is even very dangerous. People should absolutely not think that the color of their eyes predisposes them to health problems on such a level that it is necessary to change their color. »

Basically, what is the difference in eye color due to? “Brown eyes have pigment and blue eyes don’t,” says Dr.^D Robert. We see the fundus, which is dark, but by diffraction it appears blue. It’s like the sky which is blue even though the space behind it is black. »