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What causes sudden eye color change?

What causes sudden eye color change?

Sudden eye color change is a rare phenomenon that can occur due to various factors. The color of the eye is determined by the amount and quality of melanin pigment in the iris. Anything that affects melanin content or distribution in the iris can lead to eye color change. Some of the potential causes include:

Medical Conditions

Certain medical conditions can trigger a sudden change in eye color:

Fuchs Heterochromic Iridocyclitis: This condition causes inflammation and atrophy of the iris. It typically affects one eye leading to different colored eyes. The affected eye can change to a lighter shade due to depigmentation.

Horner’s Syndrome: This condition arises from damage to the sympathetic nervous supply to the eyes. It results in constriction of pupils and drooping of eyelids. The affected eye may become darker in rare cases.

Pigment Dispersion Syndrome: This is characterized by release of iris pigment into other eye structures. The colored pigment gets deposited in the clear cornea leading to a change in eye color.

Melanoma of the Iris: Iris melanoma or eye cancer can also alter eye color. The tumor may cause dark black spots on the iris. Advanced tumors can cause the entire iris to turn blackish-brown.


Physical trauma to the eyes can also induce color change:

Blunt Eye Injury: A blunt force blow to the eye can cause swelling or bruising of the iris tissue. This alters light reflection and absorption resulting in temporary color change.

Penetrating Injuries: Sharper objects like sticks, wires, knives etc penetrating the eye can permanently scar and damage the iris. This leads to irregular pigmentation and multi-colored eyes.

Chemical Burns: Exposure to strong acids or alkalis can burn the delicate iris tissue. Post-healing, the affected portion may lose pigmentation and become lighter.

Surgery: Eye surgeries like corneal transplant, cataract removal and glaucoma procedures involve instrumentation within the eye. This can potentially cause temporary or lasting trauma to the iris.


Certain prescription drugs are associated with eye color changes:

Chloroquine and Hydroxychloroquine: These antimalarial drugs frequently cause lightening of the iris color. The effect is dose-dependent and irreversible after chronic use.

Phenothiazines: This class includes antipsychotic drugs like chlorpromazine and thioridazine. A characteristic side effect is pigmentary retinopathy wherein the retina becomes mottled.

Tamoxifen: This hormonal drug may deposit pigment in the cornea and change limbal ring color in some cases. The onset is quite rapid over a few weeks.

Prostaglandin Analogs: Glaucoma medications like latanoprost and bimatoprost can induce increased pigmentation of the iris. The shade may turn darker brown over months.

Underlying Disorders

Certain disorders can contribute to eye color change indirectly:

Galactosemia: This metabolic disorder impairs the breakdown of galactose sugars. Cataracts are a common complication, and once surgically treated, may result in lighter eyes.

Neurofibromatosis: Iris hamartomas or benign growths on the iris are characteristic of this genetic disorder. The tumors can lead to heterochromia or multicolored irises.

Albinism: Lack of melanin causes extremely light eyes from birth. But later in life, some patchy pigmentation may develop, modifying the eye color slightly.

Chediak-Higashi Syndrome: This immune disorder causes oculocutaneous albinism along with increased susceptibility to infections. As in albinism, the color may evolve gradually with age.


Eye color can naturally change with advancing age due to the following aspects:

– The collagen and fat content of the cornea and iris may gradually thin out. This unmasks the darker choroidal layer underneath, making the eyes appear darker.

– The iris may depigment due to reduced cellular activity and melanin synthesis. Areas of lighter color develop within the iris causing variegated color.

– The lens becomes cloudier and starts yellowing. This lends a yellowish/brownish tint to the overall eye color.

– Inflammatory conditions like uveitis become more common. Recurring bouts lead to small scars and pigment changes in the iris.

– eyelids get droop and cause eye muscles disfunction. This result in less iris exposed and more pupil exposed, and darker color.

Pathological Myopia

In nearsighted individuals with very high myopia, the eyes elongate excessively. Due to constant stretching, the choroid layer near the iris becomes thinner and lighter. This causes the outer iris to assume a lighter shade compared to the rest of the eye.

Other Factors

A few assorted factors can also sometimes contribute to eye color transformation:

– Increased UV light exposure especially after cataract surgery, can damage iris cells and cause depigmentation.

– Environmental pollutants like chemical fumes, smoke and radiation may also potentially affect melanin content and distribution.

– Emotional stress is hypothesized to influence iris musculature and blood flow. This may produce minor temporary fluctuations in shade.

– Hormonal changes during pregnancy, puberty or menopause can theoretically have subtle effects on pigmentation.

– Rarely, a benign non-cancerous mole called nevus may develop on the iris leading to a multi-colored appearance.


To summarize, sudden eye color change has a wide array of potential causes. These include diverse medical conditions affecting the eyes, side effects of certain medications, injuries, underlying disorders and the natural aging process. Pathological myopia is another contributory factor in some cases. Accurate diagnosis requires a comprehensive ophthalmic evaluation by an eye specialist. While mostly benign, it can sometimes signal a more serious eye problem that needs medical care. Catching significant issues early is crucial to preserve vision and eye health.