The sudden appearance of a localized, raised, or bubble-like feature on the eye is often described as a “blister.” This appearance, typically occurring on the white part of the eye or the clear front surface, signals an underlying change in the eye’s delicate surface tissues. Causes range from minor irritation to serious infection. A professional eye examination remains the only reliable way to determine the exact cause and necessary action.
Common Non-Infectious Growths on the Eye Surface
Frequent causes of a raised area are slow-growing tissue changes on the conjunctiva, the clear membrane covering the white part of the eye. These growths are non-infectious and develop over time, often due to environmental factors. One condition is a Pinguecula, a yellowish, slightly raised bump usually situated near the nasal side of the eye. This growth is a deposit of protein, fat, or calcium on the conjunctiva that does not extend onto the cornea.
A Pinguecula is associated with chronic exposure to ultraviolet (UV) light, wind, or dust. While asymptomatic, it can become inflamed and cause dryness, redness, or the sensation of a foreign body. Closely related is a Pterygium, sometimes called “surfer’s eye,” which is a fleshy, wedge-shaped growth containing blood vessels. A Pterygium frequently starts as a Pinguecula but is distinguished by its potential to grow over the clear cornea.
This progression onto the cornea can affect the eye’s curvature, potentially causing astigmatism, blurred vision, or irritation. Both growths are benign, though a Pterygium that encroaches on the central visual axis may require surgical removal to preserve sight. They are long-term tissue responses rather than acute fluid-filled blisters.
Acute Fluid Accumulation (Chemosis and Cysts)
In contrast to chronic growths, some blister-like appearances result from acute fluid accumulation within the eye’s tissues. Chemosis is a condition where the conjunctiva becomes severely swollen, often ballooning out into a gelatinous, bubble-like appearance. This swelling occurs when fluid leaks from blood vessels into the tissue, typically in response to a sudden allergic reaction, severe eye irritation, or an infection.
The onset of Chemosis is usually rapid, and severe swelling can make closing the eyelids difficult. Another cause of a true clear bubble is a Conjunctival Cyst, a small, fluid-filled sac that forms when a pocket of the conjunctiva folds over itself. These cysts are transparent, mobile, and may cause irritation or excessive tearing, but they often do not cause acute pain or vision changes.
Urgent Causes Involving the Cornea
The most concerning causes involve the cornea, the clear front dome of the eye, as these can quickly threaten vision. A Corneal Ulcer, also known as keratitis, is an open sore on the corneal surface resulting from an infection (bacterial, viral, or fungal). While an ulcer is a tissue defect, the surrounding inflammation and the white or grayish infiltrate can present as a raised, opaque spot resembling a severe blister.
Corneal ulcers are frequently associated with contact lens wear, abrasions, or underlying eye disorders. Severe Viral Keratitis, such as that caused by the Herpes Simplex Virus, can also create lesions that appear raised or thickened on the corneal surface. These urgent conditions are marked by a distinct set of severe accompanying symptoms: significant pain, extreme sensitivity to light (photophobia), and noticeable blurring of vision, all requiring immediate attention.
Identifying Red Flags and Seeking Professional Care
The appearance of a blister on the eye necessitates professional evaluation to rule out conditions that can cause permanent vision loss. Several “red flags” should prompt an immediate visit to an eye care professional or an emergency room. These urgent indicators include the sudden onset of intense pain that may wake a person from sleep, or pain that feels disproportionate to the eye’s physical appearance.
Any rapid change in vision, such as sudden blurring or loss of sight, is a sign of an ocular emergency. Other concerning signs are a discharge of pus or thick fluid from the eye, or severe sensitivity to light. If a person has experienced recent eye trauma, chemical exposure, or wears contact lenses, the risk of a serious corneal issue is higher, and they should seek care promptly. Until a professional examination is performed, avoid rubbing the eye and refrain from using over-the-counter eye drops without specific medical guidance.