The question of whether eye color can change is complex, but the answer is definitively yes, though it is usually rare in a healthy adult. The color that appears in the eye is fixed by the amount of pigment contained within the iris, the muscular diaphragm that controls the size of the pupil. While this pigmentation is typically stable through adulthood, numerous factors—ranging from natural development to medical conditions and intentional procedures—can alter its hue.
How Eye Color is Determined
The color of the eye is determined by the concentration and distribution of the pigment melanin within the iris’s stroma. Individuals with high amounts of melanin will have brown or black eyes because the pigment absorbs most of the light entering the eye.
Lighter eye colors, such as blue, green, and hazel, are structural colors that rely on physics rather than pigment. People with blue eyes have very little melanin in the front layer of the iris, allowing light to scatter as it passes through the stroma. This phenomenon, known as Rayleigh scattering, causes the shorter, blue wavelengths of light to reflect back out, making the eye appear blue. Green and hazel eyes result from a moderate amount of melanin combined with this light-scattering effect, often incorporating a yellowish pigment called lipochrome to create the final hue.
Developmental Changes and Perception
The most common and natural color change occurs during infancy due to the development of pigment-producing cells. Many babies are born with light blue or gray eyes because the melanocytes in their irises have not yet been activated by light exposure. As the infant’s eyes are exposed to light over the first months of life, these cells begin to produce melanin.
Melanin production gradually stabilizes, usually by six to twelve months, or sometimes later into early childhood, causing the eyes to darken to their genetically determined adult color. Beyond this developmental period, perceived color changes in adulthood are frequently an illusion caused by external factors. Changes in lighting conditions or the color of clothing can alter the way light reflects off the iris, making the color appear different.
The size of the pupil also plays a role in perceived color variation. When the pupils dilate, such as in dim light or during periods of intense emotion, the iris contracts. This action reveals more of the darker area surrounding the pupil, making the eye appear darker or more intense without any actual change to the iris’s pigmentation.
Health Conditions and Medical Causes
A noticeable, non-temporary change in eye color in an adult may indicate an underlying medical issue, requiring examination by an eye care professional. Certain diseases can cause acquired heterochromia, where the two irises become different colors. For instance, Fuch’s heterochromic iridocyclitis is a mild, chronic inflammation that often leads to a gradual lightening of the affected eye.
Horner’s Syndrome, resulting from damage to the sympathetic nerve pathway, can cause the affected iris to become lighter or fail to darken properly. Trauma, such as a blunt force injury, can also cause a color change by damaging the iris tissue. This damage may deposit iron from bleeding, a condition called hemosiderosis, which results in a brown or reddish tint.
Specific medications are also known to cause permanent color alterations. Prostaglandin analogs, a class of eye drops used to treat glaucoma by lowering intraocular pressure, stimulate melanin production in the iris. These drops, such as latanoprost, can cause a permanent and irreversible darkening of the eye color. This effect most commonly affects lighter, mixed-color irides (green, hazel, or blue-brown), turning them brown gradually over months or years of consistent use.
Intentional Alteration Methods
For people seeking to intentionally change their eye color, the safest and most common method is the use of cosmetic contact lenses. These are tinted soft lenses that cover the iris and must be prescribed by an eye care specialist, even for non-corrective use.
More invasive, permanent methods exist but carry substantial health risks. Iris implant surgery involves placing a colored, artificial silicone disc over the natural iris. This procedure is approved for medical purposes but often not for purely cosmetic use in many countries, including the United States. Complications from cosmetic iris implants can include glaucoma, cataracts, and corneal damage, often leading to severe vision loss.
Another method involves laser depigmentation, which uses a laser to break down melanin pigments in the front layer of a brown iris to reveal the underlying blue color. This procedure is irreversible and highly controversial because the released pigment particles can clog the eye’s drainage system, leading to elevated intraocular pressure and potentially causing pigmentary glaucoma. Keratopigmentation, or corneal tattooing, involves injecting pigment into the clear outer layer of the eye to change its appearance, but this carries risks of infection and long-term corneal damage.