Eye color is one of the most distinguishing human characteristics. Almost countless shades and hues of blue, green, brown, gray and hazel are found in eyes from around the globe. Eye diseases, medical conditions and other uncontrollable factors can permanently change a person’s eye color. Those with naturally light-colored eyes tend to be more susceptible to these changes.
The iris is the colored ring of muscle surrounding the pupil. The amount of pigmentation within the iris determines its color. Three genes are responsible for the color of your eyes. Scientists understand how genetic variations result in brown, green and blue eyes. However, they are still working to understand how a person develops less common colors, like hazel and gray.
Brown is a dominant pigment, and it usually wins out over green and blue. Because blue is the most recessive, green will also win out over blue. There are exceptions to this rule, of course, and a child with a brown-eyed parent and a green-eyed parent can have green eyes. Even two brown-eyed parents can produce a blue-eyed child, if the baby receives recessive blue-eyed genes from both parents. Additionally, a child’s eye color can change over the first three years of life.
Certain medical conditions have been shown to change eye color in some patients. These conditions include Fuch’s heterochromic uveitis, pigmentary glaucoma and Horner’s syndrome.
Fuch’s heterochromic uveitis causes inflammation in the front portion of only one eye. The inflammation can cause a color change in the affected eye’s iris, and the condition increases a patient’s risk of developing glaucoma and cataracts.
Pigmentary glaucoma is characterized by the collection of pigment granules at the back of the cornea, which disrupts the back of the iris. These same granules can also accumulate at the front side of the iris. When this occurs, color changes can result, and each eye can develop a different color.
Horner’s syndrome is a condition in which the third cranial nerve is not functioning properly. The affected eye can then become lighter than the other. This condition typically affects children less than one-year old, though it occasionally occurs in adults.
The LASIK vision correction procedure does not affect eye color. The procedure shapes the cornea, which is clear and sits above the iris. A more complete description of LASIK describes exactly how LASIK works, plus its potential benefits and side effects.
However, some doctors use a different laser — unrelated to LASIK — for the strict purpose of changing eye color. This laser operates on the theory that there is blue pigment in the eyes of all brown-eyed people. This laser destroys dark pigment in the iris to reveal the blue pigment. So far, this laser is only able to create blue eyes from brown eyes.
The topical medication Latisse promises to increase the thickness and length of eyelashes. Patients use a special brush to apply it right above the lash line each night. One of the drug’s most talked-about side effects is its potential to darken some patients’ eye color. This is said to occur slowly and usually affects people with greenish-blue or hazel eyes. According to one doctor, the risk of this side effect is less than one percent, and it only happens when some of the medication gets into the eye.
Research indicates a very slight connection — if any — between eye color and visual acuity. For example, evidence suggests that the lighter the eye, the higher the risk of light sensitivity. Scientists theorize that light can more easily penetrate a pale-colored eye, similar to how light passes through sunglasses. The darker the sunglasses, the better they protect you from the sun. Lighter eyes may be more sensitive to and affected by sunlight, which increases the risk of macular degeneration. So far, these are the only ties between eye color and vision.
Some iridologists and alternative healers believe that darker eyes indicate a buildup of toxins in the body. They claim eyes become lighter as the toxins are flushed out, and the body becomes healthier. Therefore, a healthy person will have light gray or blue eyes. They generally recommend a raw food diet to remove the toxins. Cases have been reported where the color of the iris did change as a result of a raw food diet, but it is difficult for scientists to replicate these changes.
Some medications used to treat glaucoma — especially those know as prostaglandin analogs — can possibly alter eye color. These changes are more prevalent in patients with light blue and green eyes. Patients’ eyes may become darker, because these medications can increase pigment in the iris. Many people report that the color changes did not reverse after stopping the medication.
Whether your eyes are blue, green, brown, gray or hazel, unexpected changes in their appearance could be cause for concern. See your eye doctor right away if you experience any unusual symptoms.
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