Overview

Keratitis is an inflammatory condition affecting the cornea, the clear, dome-shaped outer layer of the eye that covers the iris and pupil. It can be caused by infections, injuries, or underlying health conditions. Keratitis can range from mild irritation to severe eye pain and vision loss if left untreated. Depending on its cause, keratitis is classified as infectious (caused by bacteria, viruses, fungi, or parasites) or non-infectious (caused by trauma, dry eyes, or exposure to UV light). Prompt diagnosis and treatment are essential to prevent complications and preserve vision.

Causes

The causes of keratitis can be broadly divided into infectious and non-infectious categories:

• Bacterial keratitis: Often caused by Staphylococcus aureus, Pseudomonas aeruginosa, and other bacteria, especially in contact lens wearers or following eye trauma.
• Viral keratitis: Commonly caused by the herpes simplex virus (HSV), leading to recurrent episodes of eye inflammation. Herpes zoster (shingles) can also affect the cornea.
• Fungal keratitis: Caused by fungi such as Fusarium or Aspergillus, typically following injury with plant material or in agricultural workers.
• Acanthamoeba keratitis: A rare but serious infection caused by a microscopic parasite, usually linked to poor contact lens hygiene or exposure to contaminated water.
• Non-infectious keratitis: Can result from eye injuries, foreign bodies, dry eye syndrome, exposure to ultraviolet (UV) light (photokeratitis), or autoimmune diseases.
• Contact lens-related keratitis: Improper contact lens use, overnight wearing, or poor hygiene increases the risk of keratitis.

Symptoms

The symptoms of keratitis vary depending on the severity and cause but generally include:

• Eye pain: Ranging from mild discomfort to severe pain, often worsened by blinking.
• Redness: The affected eye usually appears red and inflamed.
• Excessive tearing or discharge: Clear or purulent discharge may be present.
• Blurred or decreased vision: Vision may become cloudy or blurry, especially in more severe cases.
• Sensitivity to light (photophobia): Bright lights can cause significant discomfort.
• Foreign body sensation: A feeling of something being stuck in the eye is common.
• Corneal ulcer: In severe cases, a visible white or gray spot on the cornea may develop.

Diagnosis

Diagnosing keratitis involves a detailed eye examination by an ophthalmologist or eye care specialist. The diagnostic process typically includes:

• Medical history: Assessment of symptoms, contact lens use, recent trauma, or systemic illnesses.
• Slit-lamp examination: A magnified view of the cornea helps identify inflammation, ulcers, or lesions.
• Fluorescein staining: A special dye is used to highlight corneal damage under blue light.
• Corneal scraping: In suspected infections, a small sample is taken from the cornea for microscopic examination and culture to identify bacteria, fungi, viruses, or parasites.
• Polymerase chain reaction (PCR): Advanced molecular tests may be used to detect viral DNA, especially in herpes-related keratitis.
• Confocal microscopy: A non-invasive imaging technique that can help visualize certain infections like Acanthamoeba.

Treatment

The treatment of keratitis depends on its cause and severity:

• Bacterial keratitis: Treated with prescription antibiotic eye drops, often given frequently (every 1-2 hours) in severe cases.
• Viral keratitis: Managed with antiviral eye drops (e.g., acyclovir), oral antiviral medications, and sometimes corticosteroids under close supervision.
• Fungal keratitis: Requires antifungal eye drops (e.g., natamycin) and, in severe cases, oral antifungal medications.
• Acanthamoeba keratitis: Treated with a combination of anti-amoebic medications, which can be prolonged and challenging.
• Non-infectious keratitis: Managed with lubricating eye drops, anti-inflammatory medications, or treatment of underlying conditions (e.g., dry eyes, autoimmune disease).
• Corneal ulcers or severe keratitis: May require hospitalization, intensive eye drop therapy, or surgical interventions like debridement or, in extreme cases, corneal transplantation.
• Contact lens hygiene education: Essential for preventing recurrence in contact lens users.

Prognosis

The prognosis for keratitis varies based on the cause and promptness of treatment. Most cases of mild bacterial or non-infectious keratitis respond well to treatment with full recovery of vision. Viral keratitis can recur but is usually manageable with appropriate therapy. Fungal and Acanthamoeba keratitis are more difficult to treat and may require prolonged therapy, with a higher risk of vision impairment. Delayed treatment, especially in infectious cases, can lead to serious complications such as corneal scarring, chronic pain, or even blindness. Early diagnosis and adherence to treatment significantly improve outcomes, and proper eye care practices can reduce the risk of keratitis.