The sudden appearance of a raised, bubble-like, or fluid-filled structure on the surface of the eye can be highly alarming. This change, often described as a “blister,” represents a disruption in the delicate transparent layers protecting the eye’s front surface. The white part of the eye (sclera) is covered by the conjunctiva, a clear membrane where most of these growths originate. While many causes are benign tissue changes, others represent immediate threats to vision requiring swift medical intervention. Any unexpected elevation or change in the eye’s surface texture should prompt an examination by an eye care professional.
Non-Infectious Surface Growths
Non-infectious growths are long-term tissue responses to environmental exposure, appearing as solid, non-fluid growths on the conjunctiva. Primary factors contributing to their formation include exposure to ultraviolet (UV) radiation, chronic wind, and dust.
A Pinguecula is a yellowish, slightly raised patch typically found closer to the nose. Composed of protein, fat, and calcium deposits, it represents solar-induced tissue degeneration. Pingueculae remain confined to the conjunctiva and do not grow onto the cornea. Management involves observation and lubricating eye drops to alleviate dryness and irritation.
A Pterygium (“surfer’s eye”) is a fleshy, triangular growth that is more advanced. It extends outward from the conjunctiva, across the limbus (the border between the cornea and the sclera), and onto the cornea itself. This progression can cause blurred or distorted vision by changing the cornea’s shape.
If a Pterygium interferes with vision or causes persistent discomfort, surgical removal may be necessary. Because recurrence is a concern, surgeons often employ conjunctival autografting, transplanting the patient’s own healthy conjunctiva to the surgical site. Both growths are slow to develop and indicate cumulative environmental damage. Protecting the eyes with UV-blocking sunglasses is the most effective way to slow their progression.
Fluid-Filled Swelling and Cysts
When the eye looks like it has a blister, the cause is often fluid accumulation beneath the conjunctiva, known as Chemosis. Chemosis is significant edema, or swelling, of the conjunctival tissue. The conjunctiva becomes so swollen that it appears translucent and gelatinous, resembling a large, clear bubble covering the white of the eye.
Chemosis signals severe irritation or inflammation, commonly triggered by acute allergic reactions, trauma, or post-surgical changes. During an allergic response, histamine release causes conjunctival blood vessels to leak fluid into the tissue. Severe swelling can prevent the eyelids from closing, potentially leading to rapid drying and corneal damage.
Conjunctival Cysts are small, localized, fluid-filled sacs, distinct from Chemosis. They can form as retention cysts when accessory tear gland ducts become blocked, leading to secretion buildup. Alternatively, inclusion cysts form when a small piece of the outer epithelial layer becomes trapped underneath.
These cysts are typically benign, appearing as a single, clear or yellowish bump, unlike Chemosis. They may cause irritation or a foreign body sensation but are usually painless unless inflamed. Small cysts are managed with observation or lubricating drops; larger, symptomatic cysts can be treated by aspiration or surgical excision to prevent recurrence.
Infectious and Ulcerative Threats to Vision
The most serious causes of a blister-like appearance involve damage and infection to the cornea, the clear structure at the front of the eye. A Corneal Ulcer is an open sore that typically appears as a white or gray spot, which may be raised or look like a blister with a cloudy base. This condition is a medical emergency because the ulcer represents an active infection destroying corneal tissue.
Corneal ulcers (infectious keratitis) are often caused by bacteria, fungi, or viruses; contact lens wear is a major risk factor. Symptoms are severe, including intense eye pain, decreased vision, extreme sensitivity to light (photophobia), and thick pus-like discharge. Viral keratitis, particularly from the Herpes Simplex Virus, can also cause a raised, blister-like lesion on the cornea with a characteristic branching pattern.
Since these infections can lead to permanent vision loss or blindness within 24 to 48 hours, immediate medical attention is mandatory. The need for an urgent appointment versus an emergency room visit is based on symptom severity. Any lesion on the clear cornea accompanied by sudden vision loss, severe pain, or recent chemical exposure requires an immediate trip to the emergency room.
When to Seek Emergency Care
Symptoms such as sudden vision loss, a foreign body embedded in the eye, or a chemical burn necessitate immediate, high-level care to stabilize the condition. For less dramatic symptoms—like a red, irritated eye with mild discharge but without severe pain or sudden vision change—an urgent appointment with an ophthalmologist within 24 hours is appropriate. If any doubt exists regarding severity, seeking emergency care immediately remains the safest course of action.