Jeremy Wingard, M.D.
Glaucoma Fellow and Clinical Instructor
University of Pittsburgh Medical Center

Jessie, Colorado, USA

Does iris color affect vision?

Jeremy Wingard
Glaucoma Fellow and Clinical Instructor,
UPMC Eye Center,
University of Pittsburgh Medical Center,
former HHMI medical fellow

There is not any known association between iris color and either visual acuity or color vision. Several factors do influence central visual acuity (which we test using the Snellen eye chart), including media clarity (clear cornea, quiet anterior chamber, noncataractous lens, and transparent vitreous cavity), proper functioning of the photoreceptor and ganglion cells of the central retina (the macula and its central fovea), healthy optic nerve containing the ganglion cell axons (which can be damaged in glaucoma or other optic neuropathies), intact circuitry through the optic chiasm and radiating to the occipital cortex, and, finally, and proper functioning of the cortex itself.

Color vision results from a similar pathway of clarity and proper connectivity, although optic nerve disease (for example, swelling of the optic nerve due to elevated intracranial pressure) specifically affects color vision even before it affects central visual acuity.

 

The iris is useful, of course, even if it’s not directly involved in visual acuity or color vision. It creates the pupil, the aperture through which light enters the back of the eye and shines onto the retina. Without the iris, light rays from any angle enter the posterior segment of the eye, and this is indeed a problem after traumatic or congenital aniridia, or absence of the iris. Glare is the most obvious consequence of this condition.

 

Iris color is genetic, and a number of eye diseases have genetic associations. Therefore, you might find a family in which most members have both glaucoma and brown eyes. These associations are familial, though, and do not indicate brown eyes and glaucoma are directly linked.

02/16/10 10:41