The color of your eyes is determined by the amount and distribution of melanin, a dark pigment, within the iris stroma. Brown eyes have a high concentration of this pigment, which absorbs light and accounts for their deep coloration. While a true loss of brown pigment in an adult is exceedingly rare, changes in the cornea or lens can alter how light reflects from the iris. This creates the visual illusion of a duller or greyer shade.
The Stability of Adult Eye Color
Final eye color is typically complete in early childhood, usually stabilizing between nine months and six years of age. This permanent color is fixed once melanocytes have established their adult level of pigment production in the iris. Since brown eyes result from a high melanin concentration, the pigment provides a stable color resistant to change in adulthood.
Unlike lighter eyes, which rely on light scattering, brown eyes get their color from absorption. A true shift from a heavily pigmented brown iris to a grey color would involve a highly unusual loss of established melanin. Therefore, if you perceive a change to a grey hue, the cause is likely an obstruction or a change in the environment surrounding the iris, rather than the iris pigment itself.
Common Causes of Apparent Greying
The most frequent reasons an eye might appear greyish involve changes to the transparent structures that sit in front of the iris.
Arcus Senilis
One common cause is a condition known as arcus senilis, or arcus juvenilis if it occurs in a younger person. This condition appears as a white, grey, or bluish ring around the outer edge of the cornea. The ring is caused by lipid deposits, such as cholesterol, accumulating in the peripheral cornea. This deposit masks the iris’s outer border, making the eye appear duller or cloudier. Arcus senilis is common in older adults. However, arcus juvenilis in individuals under 40 can sometimes indicate abnormally high cholesterol levels or other underlying health conditions that warrant medical investigation.
Cataracts
Another frequent cause of a hazy or dull appearance is the development of a cataract. The lens, which sits directly behind the iris and pupil, is normally crystal clear. A cataract forms when proteins within this lens begin to break down and clump together, causing the lens to become cloudy. As the cataract progresses, it scatters the light entering the eye, which can make the pupil and the entire eye appear hazy, milky, or greyish-white. This clouding visually obstructs the brown pigment of the iris, making it look less vibrant and sometimes appearing grey.
Specific Medical Conditions Affecting Eye Appearance
Certain less common medical conditions can also cause the eye to take on a grey or dull appearance.
Uveitis
Inflammation within the eye, known as uveitis or iritis, can lead to a cloudy appearance that mimics a color change. Inflammation of the uvea introduces inflammatory cells and proteins into the eye’s fluid, causing haziness, pain, redness, and light sensitivity. This internal inflammation can cause the cornea to become slightly bluish or cloudy, which may be interpreted as a greyish hue over the iris. Uveitis is a serious condition that requires prompt medical treatment to prevent secondary issues like glaucoma or vision loss.
Kayser-Fleischer Rings
Another rare but distinct cause is the presence of Kayser-Fleischer rings, which are associated with Wilson’s disease, a genetic disorder involving excessive copper accumulation. These rings are copper deposits that form in the peripheral cornea, appearing as brown, golden, or grayish-green circles that encircle the iris. The grayish-green appearance is sometimes noted as the source of the perceived greying.
Medication Effects
Certain topical eye medications, specifically prostaglandin analogues used to treat glaucoma, can also induce changes in the iris. These medications typically cause the iris to darken by increasing melanin production, often turning mixed colors more uniformly brown, which is a true pigment change.
When to Consult an Eye Care Professional
Any noticeable or persistent change in the appearance of your eye warrants a comprehensive examination by an optometrist or ophthalmologist. A professional can use a slit lamp microscope to definitively diagnose the underlying cause, distinguishing between benign conditions and those requiring immediate attention. You should seek an evaluation if you notice the change is rapid, asymmetrical, or accompanied by other symptoms.
Symptoms such as eye pain, sudden vision loss, persistent redness, excessive light sensitivity, or the presence of floaters should prompt an urgent visit to an eye care specialist. Conditions like uveitis and rapidly progressing cataracts need timely diagnosis to manage inflammation and preserve vision. While the perceived greying of a brown eye is most often a harmless visual effect, only a thorough clinical assessment can provide an accurate diagnosis and appropriate course of action.