By Dr. David Christensen

Dr. David Christensen

The Iris

 The colored part of the eye is actually a combination of two muscles collectively called the iris.  The iris functions as a dynamic aperture, allowing only a limited amount of light into the eye.  In dim light the dilator pupillae muscle contracts and the sphincter pupillae muscle relaxes, opening the aperture allowing more light to enter the eye.  In bright light, the opposite is true; the dilator pupillae muscle relaxes and the sphincter pupillae muscle contracts, closing the aperture allowing less light to enter the eye. 

Iris color is a result of pigmentation.  Pigment acts to block light from entering the eye.  The most common colors are brown, blue and green.  Eye color is genetic and is the result of influences from both mother and father, but is not a simple blend of color from both parents.  The genetic influences of eye color are not fully understood.

You may not know that eye color can change over time and may a result from several different factors.  Many young children are born with light-colored eyes that gradually become darker during the first few years of their life.  Other eye color changes may be the result of eye disease.  For example, pigmentary glaucoma, Fuch’s heterochromic iridocyclitis, and Horner’s syndrome can all result in changes to eye color.  Furthermore, some medications can alter eye color.  Prostaglandin glaucoma medications have been known to modify eye color over time.  Furthermore, the brilliant colors of youthful eyes can fade and dull over time.  If your eye color changes suddenly, please seek care immediately.  The eye doctors at Iowa EyeCare always welcome new patients.

Contact lenses now give you a choice in your own eye color.  Colored contact lenses are a medical device and require a prescription from an eye doctor.  Never purchase lenses from friends or from a beauty shop.  The damage from contact lens abuse can cause permanent vision loss.  If you are interested in colored contact lenses contact Iowa EyeCare in Marion, Robins, or Cedar Rapids, Iowa, today!

Genetics and Eye Color