A scleral cyst is a benign, fluid-filled sac that develops on the sclera, the tough, white outer layer of the eyeball. These cysts can differ in size and appearance, from small blemishes to larger, more prominent structures. They are self-contained, with a distinct membrane that separates them from the surrounding eye tissue. While benign, their presence can sometimes lead to discomfort or visual disturbances.
Causes and Types of Scleral Cysts
Scleral cysts are categorized into two groups based on their origin: congenital and acquired. Congenital cysts are present from birth and occur because of abnormal development of the eye’s structures during the embryonic stage. This can involve the trapping of surface tissues during the formation of the eyeball, leading to a cyst that may not be noticed until later in life.
Acquired cysts, which develop after birth, are more common and can result from several factors. Ocular surgery is a frequent cause, where a small piece of the conjunctiva, the clear membrane covering the sclera, is accidentally implanted into the scleral layer. This is sometimes seen after procedures to correct strabismus (crossed eyes), repair a retinal detachment, or after cataract surgery.
Trauma to the eye is another cause of acquired scleral cysts. An injury can displace surface epithelial cells into the deeper scleral tissue, where they can multiply and form a fluid-filled cyst. Less frequently, chronic inflammation of the sclera, a condition known as scleritis, or certain parasitic infections can also trigger the formation of these cysts. In some instances, they may appear spontaneously without any identifiable cause.
Associated Symptoms and Complications
The experience of a scleral cyst varies depending on the cyst’s size and location. Many small cysts are asymptomatic and are often discovered incidentally during a routine eye exam. When symptoms do arise, they are related to the physical presence of the cyst on the surface of the eye.
A noticeable bump on the white of the eye is a clear sign and can be a cosmetic concern. Other symptoms of larger cysts include:
- A persistent foreign body sensation
- Localized irritation
- Excessive tearing
- Visible redness over and around the cyst
While most scleral cysts are harmless, complications can occur, particularly with cysts that are large or continue to grow. A growing cyst can press on the cornea, inducing astigmatism—an imperfection in the eye’s curvature—which results in blurred or distorted vision. A large cyst might also physically obstruct a portion of the visual field. Rarely, a cyst can rupture, leading to more significant inflammation or a secondary infection.
Diagnosis and Medical Evaluation
Diagnosing a scleral cyst begins with a clinical examination by an eye care professional. This includes a visual inspection of the eye and a review of the patient’s medical history for previous eye surgeries, injuries, or inflammatory conditions.
A slit-lamp examination is a standard part of the evaluation. This instrument provides a magnified, three-dimensional view of the eye, allowing the doctor to assess the cyst’s size, shape, transparency, and location. It also helps evaluate the health of surrounding tissues.
If a cyst is large, opaque, or appears complex, advanced imaging may be used. Ultrasound biomicroscopy (UBM) uses high-frequency sound waves to create a detailed cross-sectional image of the front of the eye. This allows an ophthalmologist to determine the cyst’s depth and internal characteristics, confirming it is fluid-filled.
Management and Treatment Approaches
The management for a scleral cyst is based on the presence of symptoms and its impact on vision. For small, asymptomatic cysts, the most common strategy is observation. An eye care professional will monitor the cyst during regular check-ups to ensure it is not growing or causing problems.
When a cyst becomes symptomatic, treatment is considered. One intervention is needle aspiration, where a fine needle is used to drain the fluid. This procedure can provide immediate relief but has a high rate of recurrence because the cyst wall is left intact and can refill.
For a more permanent solution, surgical excision is performed. This procedure involves removing the entire cyst wall to prevent it from growing back. The surgical technique may vary depending on the cyst’s size and location, sometimes requiring a tissue graft to cover the area after removal. Excision is reserved for cysts that cause persistent discomfort, interfere with vision, or are a cosmetic concern.