Definition

Keratitis is the inflammation of the cornea. Eye cornea is the transparent membrane covering the outermost part of the eye. The cornea serves to protect the eyes from dust, germs, and other harmful particles, as well as to focus incoming light. Disruption of the corneal structure due to injury or infection impairs these functions.

Though specific data on keratitis in Indonesia is unavailable, it contributes to 10% of visual impairment cases. In India, approximately 2 million individuals develop keratitis that progresses to corneal ulcers annually.

Causes

Keratitis can be caused by both infectious and non-infectious factors. Keratitis caused by infection is usually caused by bacteria, viruses, fungi, and parasites. Meanwhile, non-infectious keratitis is caused by the use of contact lenses or foreign particles entering the eye.

Here is a further explanation of the causes of keratitis:

Infectious Keratitis

1. Bacterial Infection: Common bacteria include Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pneumoniae, and Pseudomonas aeruginosa. More severe cases may involve Neisseria gonorrhoeae, Neisseria meningitidis, Corynebacterium diphtheriae, and Haemophilus influenzae.  
2. Viral Infection: The Herpes Simplex Virus (HSV) type 1 frequently causes keratitis, while HSV type 2 is less common. The varicella-zoster virus, responsible for herpes zoster, can also infect the eyes.
3. Fungal Infection: Yeast-type fungi (Candida) or mold (Aspergillus) are typical culprits.
4. Parasitic Infection: Acanthamoeba is a parasite that causes keratitis, thriving in soil, fresh water, sea water, and the respiratory tract. The risk increases with contact lens use, especially with poor hygiene.

Non-Infectious Keratitis

The most common cause of keratitis that is not caused by infection is an injury to the cornea. Injuries can occur due to scratches or trauma that causes inflammation. Corneal injuries can also lead to bacterial infections because scratches on the cornea allow germs to enter the eye.

Some other conditions that can cause keratitis include:

• Improper use of contact lenses
• Excessive exposure to sunlight, this condition is called photokeratitis
• Weak immune system
• Vitamin A deficiency
• Dry eye disease

Risk Factor

While keratitis can affect anyone, certain conditions increase the likelihood of developing the condition. The risk factors vary depending on the cause of keratitis:

Bacterial Keratitis

• Prolonged contact lens wear, including during sleep or swimming
• Corneal injury or history of eye surgery, such as LASIK
• Eyelid or external eye conditions like blepharitis, dry eyes, trichiasis, and entropion
• Conditions that lower immunity, such as diabetes and vitamin A deficiency

Fungal Keratitis

• Long-term use of corticosteroid eye medication
• Immunosuppressive conditions
• Eye injuries from plant or agricultural equipment
• Surface eye diseases
• Poor hygiene or improper contact lens use

Viral Keratitis

Risks of viral keratitis can increase in immunocompromised states due to certain diseases, lack of nutritions or malnutrition, or allergic eye diseases.

Parasitic/Amebic Keratitis

Parasites that can cause keratitis generally live in soil or water. Risks of parasitic keratitis will increase if you have contact with contaminated soil or water. Poor contact lens hygiene, such as using tap water for cleaning or not disinfecting lenses properly, can increase the risk of parasitic keratitis.

Symptoms

Keratitis often affects only one eye but can occur in both. Common symptoms include:

• Eye redness 
• Eye pain
• Excessive tearing or eye discharge
• Difficulty opening the eye due to pain or inflammation
• Blurred or unfocused vision
• Sensitivity to light (photophobia)
• Feeling of something in the eye (foreign body sensation)

Diagnosis

A thorough eye examination is required to diagnose keratitis. This includes taking a detailed medical history of symptoms and health examinations to identify risk factors and potential causes of symptoms. The doctor will examine the eyes for signs and severity by examining the eye structure, visual acuity, and conduct slit-lamp examinations. 

Laboratory tests of eye fluid or eye tissue can be conducted if needed, to determine the cause of keratitis. These tests can also help in determining the right treatments for patients.

Management

Treatment depends on the cause and severity of keratitis. Mild cases may only require artificial tears. Symptoms usually resolve on their own, but if they persist for more than 24 hours, prescription eye drops may be necessary.

Meanwhile, keratitis caused by infection requires several specific treatments according to the cause, namely:

1. Bacterial keratitis: Mild cases are treated with antibiotic eye drops, while moderate to severe cases may require oral antibiotics.
2. Fungal keratitis: Requires antifungal eye drops or oral medications.
3. Viral keratitis: Treated with antiviral eye drops and oral medications, along with artificial tears.
4. Parasitic keratitis: Particularly challenging to treat. Antibiotic eye drops may be used, but some parasites may not respond to them. Severe cases might necessitate a corneal transplant.

Complications

Untreated or improperly managed keratitis can lead to serious complications, including:

• Corneal inflammation and scarring
• Recurrent viral corneal infections
• Corneal ulcers or open wounds
• Permanent vision impairment
• Blindness

Prevention

Preventing keratitis primarily involves maintaining ocular hygiene and overall eye health, alongside mitigating potential injuries. Key preventive measures, particularly for contact lens users, include:

• Removing contact lenses before sleep
• Avoiding contact lens use while swimming
• Ensuring hands are washed, cleaned, and dried before handling contact lenses
• Utilizing specialized contact lens cleaning solutions
• Regularly replacing contact lenses according to manufacturer guidelines or upon noticing any damage

Additionally, preventing viral infections is crucial. For individuals with viral infections like chickenpox or herpes, it is vital to avoid touching the eyes or eyelid area without thoroughly washing hands. Always use prescribed eye drops as directed by a physician and maintain hand hygiene through regular washing with soap and water or hand sanitizer to minimize viral transmission.

When to See a Doctor?

Keratitis requires prompt medical intervention. If symptoms indicative of keratitis arise, it is imperative to consult an ophthalmologist immediately. Early treatment is essential to prevent serious complications, including potential blindness.

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