Keratitis is inflammation of the cornea, the clear, dome-shaped outer layer at the front of the eye. Disciform keratitis is a specific form of this inflammation, characterized by a central, immune-mediated swelling within the corneal tissue. This condition can temporarily or permanently affect vision, but it is typically manageable with appropriate medical intervention. It is one of several ways that underlying viral exposure can manifest in the eye.
Understanding Disciform Keratitis
The term “disciform” describes the characteristic physical appearance of the condition, which presents as a circular or disc-shaped area of swelling and clouding in the cornea. This swelling, known as edema, primarily occurs in the corneal stroma, which is the thick, middle layer of the cornea.
The physical pathology often originates from dysfunction of the corneal endothelium, the innermost layer responsible for pumping fluid out of the stroma. When the endothelial cells are damaged or inflamed, they can no longer maintain the cornea’s dehydrated state, causing fluid to accumulate in the stroma. This fluid accumulation leads to corneal thickening and the hazy, ground-glass appearance seen upon examination. Other signs of this process include the presence of keratic precipitates, which are clumps of inflammatory cells that adhere to the back surface of the cornea.
Primary Causes and Immune Response
The most frequent cause of disciform keratitis is a previous infection with the Herpes Simplex Virus (HSV), typically the HSV-1 strain. Unlike other forms of herpetic eye disease, disciform keratitis is generally not caused by active viral replication within the corneal stroma. Instead, it is classified as a delayed hypersensitivity reaction, meaning the body’s immune system is overreacting to residual viral antigens.
The virus establishes a latent infection in the trigeminal nerve ganglion, and when it reactivates, viral proteins or parts of the virus can reach the cornea. The immune system then launches an inflammatory response against these foreign substances, causing the damage and swelling. This immune response is the primary driver of the corneal damage, not the virus itself. Other less common viruses, such as the Varicella Zoster Virus (VZV), which causes chickenpox and shingles, can also trigger this specific type of inflammatory reaction.
Recognizing Symptoms and Diagnosis
Patients experiencing disciform keratitis often report symptoms related to the corneal swelling and inflammation. Blurred or hazy vision is the most common complaint, which is a direct consequence of the edema and clouding in the central part of the cornea. Light sensitivity, or photophobia, is also a prominent symptom, along with eye redness and a dull ache or foreign body sensation in the affected eye.
A definitive diagnosis relies on a thorough eye examination using a slit lamp microscope. This device allows the eye care professional to view the cornea under high magnification. The characteristic finding is the disc-shaped area of stromal edema and haze, which sharply delineates the affected tissue. Associated signs visible during the examination include folds in Descemet’s membrane and keratic precipitates. While the diagnosis is predominantly clinical, the patient’s history of prior herpetic infection can support the confirmation.
Treatment Strategies and Recurrence Prevention
Treatment for disciform keratitis focuses on controlling the inflammation and preventing viral reactivation. Because the condition is primarily an immune reaction, the mainstay of treatment involves the use of topical corticosteroids, such as prednisolone acetate eye drops. These anti-inflammatory medications are necessary to reduce the swelling and prevent permanent corneal scarring that could lead to vision loss.
To minimize the risk of a true viral infection while using steroids, which can suppress the local immune response, antiviral medication is frequently prescribed. Oral antivirals like acyclovir or valacyclovir are used concurrently with the steroid drops, a strategy designed to manage the inflammation while suppressing potential viral replication. Corticosteroid treatment requires close monitoring by an eye specialist due to the potential for side effects, including elevated intraocular pressure.
Disciform keratitis has a risk of recurrence. Long-term recurrence prevention strategies often involve a low-dose daily regimen of oral antiviral medication, known as prophylactic therapy. Studies have shown that this approach can significantly reduce the frequency of future episodes of herpetic eye disease. This preventative treatment is often recommended for high-risk patients to protect the cornea and preserve long-term visual function.