Band Keratopathy is a degenerative eye condition characterized by the formation of a horizontal, opaque band across the cornea, the clear, dome-shaped front surface of the eye. This opacity develops from the precipitation of calcium salts, specifically calcium phosphate, within the superficial layers of the cornea. The accumulation of these deposits causes progressive clouding of the visual axis, resulting in decreased vision over time. It is considered a form of corneal degeneration that can significantly affect a person’s quality of life.
Symptoms and Appearance
Patients with this condition often experience symptoms related to the deposit’s location and density. A common complaint is a gradual decrease in visual acuity as the grayish-white band thickens and moves into the center of the cornea. When the deposits become thick enough, they can cause the surface layer of the cornea (the epithelium) to become irregular or flake off. This leads to irritation, eye pain, and a foreign body sensation described as having sand or grit in the eye.
Clinically, the condition presents as a whitish-gray opacity that typically spans the area exposed between the eyelids, known as the interpalpebral zone. This band is often concentrated in the Bowman’s layer and the subepithelial stroma, the outermost structural parts of the cornea. A distinctive feature is the small, clear gaps or holes within the band, corresponding to the corneal nerves passing through the affected layer. This sometimes gives the opacity a characteristic “Swiss cheese” pattern.
The extreme edges of the cornea, near the limbus, are commonly spared from the calcium deposition. This sparing is thought to be due to a buffering effect provided by the blood vessels located at the limbus, which may help stabilize the local environment. The severity of the symptoms, including light sensitivity (photophobia), directly correlates with the density of the calcium deposits and how much of the central visual axis they cover.
Underlying Causes of Calcium Buildup
The precipitation of calcium salts in the cornea is classified into two types: metastatic and dystrophic calcification. Metastatic calcification is related to systemic disorders that lead to abnormally high levels of calcium or phosphate in the bloodstream, such as hypercalcemia. Chronic kidney failure is a frequent systemic cause because it disrupts the body’s ability to regulate both calcium and phosphate levels.
Other systemic conditions that can prompt this type of calcium deposition include hyperparathyroidism (excessive parathyroid hormone secretion) and sarcoidosis, an inflammatory disease that can lead to increased calcium production. In these cases, calcium is deposited in the cornea due to localized changes in the tear film or aqueous humor. Increased alkalinity (pH changes) causes the calcium phosphate salts to precipitate out of the solution.
Dystrophic calcification occurs when calcium is deposited locally in the eye due to chronic inflammation or localized tissue damage, even when systemic calcium levels are normal. Long-standing ocular diseases like chronic uveitis (inflammation of the middle layer of the eye) are primary local culprits. Other damaging conditions include severe ocular trauma, prolonged glaucoma, and exposure to certain substances, such as intraocular silicone oil used in retinal surgery or phosphate-containing eye drops.
In dystrophic cases, the calcium deposition is a consequence of the damaged corneal tissue itself, which provides a site for the salts to accumulate. Though less common, rare hereditary forms involving genetic predispositions to corneal calcification also exist. Identifying and managing the underlying systemic or local cause is crucial, as failure to do so significantly increases the likelihood of the band keratopathy recurring after treatment.
Medical Procedures for Removal
The primary goal of treatment is to safely remove the calcium deposits to restore visual clarity and alleviate irritation and pain. The most common initial procedure is chelation therapy using a solution of Ethylenediaminetetraacetic Acid (EDTA). EDTA is a chemical agent that works by binding to the calcium ions, effectively dissolving the deposits from the corneal tissue.
The procedure typically begins with the manual removal of the corneal epithelium, the outermost layer, using a surgical blade or instrument to expose the calcified Bowman’s layer. A solution, often 3% EDTA, is then applied to the affected area via a soaked sponge or applicator for several minutes while the surgeon gently scrapes the deposits away. This technique is often performed in an outpatient setting under topical anesthesia.
For deeper or more extensive calcium deposits, or when a smoother corneal surface is required, Phototherapeutic Keratectomy (PTK) may be used. PTK involves the precise use of an excimer laser to ablate (vaporize) the calcified tissue. Unlike manual scraping, the laser offers a high degree of control over the depth and area of removal, resulting in a smoother corneal surface that reduces irregularities.
Regardless of the method used, the eye requires careful post-procedure management to heal the resulting epithelial defect. This care often involves a bandage contact lens, along with antibiotic and anti-inflammatory eye drops, which may include mild topical steroids. While treatment is effective at removing the existing band, the long-term prognosis depends on successfully addressing the underlying systemic or local condition to prevent the deposits from returning.