The white part of your eye is the sclera, covered by the thin, transparent conjunctiva. Brown discoloration appearing on this surface can range from harmless pigment deposits to growths or, rarely, signs of a systemic health issue. Understanding the origin involves distinguishing between localized spots and changes reflecting an internal condition.
Benign Causes of Localized Pigmentation
Many brown spots result from melanin, the natural pigment that colors skin and hair. This common and harmless physiological pigmentation is called conjunctival melanosis. It appears as flat, diffuse patches, often bilateral, and is common in individuals with darker skin tones. These spots are usually present from birth or early childhood and remain stable throughout life.
A conjunctival nevus is a separate localized spot, essentially an eye freckle or mole. These are solitary, well-defined lesions that can be flat or slightly raised and may contain small, fluid-filled cysts. Like skin moles, nevi are typically benign but require occasional monitoring by an eye care professional for changes in size or appearance. Exposure to ultraviolet (UV) radiation can contribute to the formation and darkening of both melanosis and nevi.
Structural Changes and Surface Deposits
Brown or yellowish-brown patches can also represent structural changes or tissue growths, distinct from flat pigment deposits. A common example is a pinguecula, a yellowish, slightly raised bump typically located on the conjunctiva near the cornea’s edge. These growths consist of fat, protein, and calcium deposits and are associated with chronic irritation from wind, dust, and sun exposure.
A related, potentially more aggressive growth is the pterygium, sometimes called “surfer’s eye,” which appears as fleshy, wedge-shaped tissue. While a pinguecula stays confined to the conjunctiva, a pterygium can extend across the cornea, potentially distorting vision. Although often pink or red due to visible blood vessels, pterygia can also take on a brownish-yellow hue from environmental deposits or tissue changes.
Systemic Health Conditions
In less frequent cases, brown discoloration on the sclera can be a secondary symptom of a systemic health issue or medication use. For example, long-term use of the antibiotic minocycline can cause blue-gray or blue-black hyperpigmentation of the sclera and conjunctiva. This discoloration occurs because the drug accumulates in the eye’s tissues, often appearing as a band near the limbus, and may persist after the medication is discontinued.
Another cause is Ochronosis, a rare metabolic disorder linked to alkaptonuria, which causes homogentisic acid to accumulate in connective tissues. This results in dark, often symmetrical, brown-black or bluish-black patches on the sclera. These ocular signs may appear years before other systemic symptoms, such as joint issues. Diffuse hyperpigmentation on mucous membranes, including the conjunctiva, can also signal Addison’s Disease, an endocrine disorder where the adrenal glands do not produce enough hormones. This lack of cortisol production increases the level of a hormone that stimulates melanin production, causing a generalized darkening of the skin and mucous membranes.
When to Seek Professional Evaluation
While many instances of brown eye discoloration are benign, a professional eye examination is the appropriate first step for any new or changing spot. An eye care specialist, such as an optometrist or ophthalmologist, uses a slit lamp microscope to examine the spot’s characteristics, depth, and potential for growth. This inspection helps determine if the discoloration is a harmless nevus or a more concerning lesion, such as primary acquired melanosis.
Prompt evaluation is necessary if you notice a rapid increase in the size, shape, or color intensity of an existing spot. Other warning signs include a raised or nodular appearance, associated vision changes, or the onset of pain or discomfort. If the discoloration is accompanied by generalized symptoms like unexplained fatigue, weight loss, or changes in skin color, a comprehensive medical workup is recommended to rule out a systemic condition. Even for spots confirmed as benign, regular monitoring, often every six to twelve months, is necessary.