Interstitial keratitis is the inflammation of the connective tissue of the cornea (the clear window on the front of the eye), which can lead to vision loss.

Interstitial keratitis is a serious condition, in which blood vessels grow into the cornea. Such growth can cause loss of the normal transparency (clarity) of the cornea. This condition is often caused by infections and may cause severe visual problems.

Syphilis is the most common cause of interstitial keratitis, but rare causes include leprosy and tuberculosis. Most cases in the developed world occur in patients with fully established syphilis.

In the US, most cases of syphilis are recognized and treated before they reach this stage. However, interstitial keratitis is the most common cause of blindness in the world, with cases caused by trachoma and onchocerciasis (river blindness) being very common in parts of Asia and Africa.

• Eye pain
• Photophobia
• Excessive tearing

Interstitial keratitis can be easily diagnosed by physical examination of the eyes with slit lamp examination. Blood tests and chest x-rays will usually be needed to confirm the infection causing the condition.

The underlying disease must be treated. Treatment of the cornea with corticosteroid drops may minimize scarring, and help preserve the clarity of the cornea.

If interstitial keratitis is diagnosed early and treated effectively, the corneal clarity and thus good vision will be preserved.

Once corneal clarity is lost, corneal transplantation is required. The recovery is long and arduous, and corneal transplantation is not as successful for interstitial keratitis as it is for most other corneal diseases. The presence of blood vessels in the diseased cornea brings white blood cells to the newly transplanted cornea and increases the risk of rejection.

All patients with interstitial keratitis will be closely followed by an ophthalmologist and a medical specialist with expertise in the underlying disease. Any worsening pain, increasing redness or decreasing vision should be evaluated immediately. This is particularly crucial for patients with corneal transplants.

Prevention consists of avoiding the underlying infection, and if infected, receiving prompt and thorough treatment and follow-up.