Infectious keratitis, also known as a corneal ulcer, is an inflammation of the cornea, the clear, dome-shaped front surface of the eye. This condition occurs when microorganisms infect the cornea, leading to inflammation and potential damage. It is a serious, vision-threatening condition that requires prompt medical attention to prevent permanent vision loss.
Understanding the Causes
Infectious keratitis can be caused by various microorganisms, including bacteria, viruses, fungi, and parasites.
Bacterial Keratitis
Bacterial keratitis is common, often linked to organisms like Staphylococcus aureus, Staphylococcus epidermidis, and Pseudomonas aeruginosa. These bacteria can grow on contact lenses or cases if not properly cleaned.
Viral Keratitis
Viral infections, frequently caused by the herpes simplex virus or the varicella-zoster virus (which causes chickenpox and shingles), can also lead to keratitis.
Fungal Keratitis
Fungal keratitis, though less common in temperate regions, is more prevalent in agricultural areas and can result from eye trauma involving plant material, with Fusarium and Candida species being common culprits.
Parasitic Keratitis
Parasitic infections, primarily Acanthamoeba keratitis, are caused by microscopic, single-celled organisms often found in water sources like tap water, swimming pools, or hot tubs.
Several factors increase susceptibility to infectious keratitis. Improper contact lens hygiene is a primary risk factor, including wearing lenses longer than recommended, sleeping in them, or not cleaning and disinfecting them properly. Eye injuries or trauma, even minor scratches, can create openings for microorganisms. A weakened immune system, due to illness or certain medications, can also leave the eye more vulnerable to infections. Pre-existing eye conditions or exposure to contaminated water can also increase the risk.
Key Symptoms to Watch For
Infectious keratitis often presents with noticeable eye changes. Individuals commonly experience sudden eye pain, which can be intense and persistent. The affected eye typically appears red and irritated, sometimes described as bloodshot.
Vision can become blurred or decreased, impacting clarity and sharpness. Excessive tearing or a discharge, which may appear watery or yellowish, can also be present. Sensitivity to light, known as photophobia, making bright environments uncomfortable. Many people also report a feeling that something is in their eye, a gritty or sandy sensation. These symptoms develop rapidly, requiring immediate medical evaluation.
Diagnosing and Treating the Infection
Diagnosing infectious keratitis begins with a thorough eye examination by an eye care professional. The doctor assesses the cornea for signs of inflammation and infection. To identify the specific microorganism, a crucial step involves culturing a sample from the infected eye.
Diagnostic Methods
Corneal scraping, where a small sample of cells is gently collected from the corneal surface, is the preferred initial method for obtaining material for culture. This sample is then sent to a laboratory to grow and identify the pathogen, which guides the selection of appropriate treatment. In some cases, if the infection is deep or unresponsive to initial treatment, a corneal biopsy may be performed to obtain a tissue sample for more detailed microbiological and histopathological analysis, as culturing alone can sometimes miss the causative organism. Polymerase chain reaction (PCR) tests and in vivo confocal microscopy can also complement the diagnosis, especially for difficult-to-culture organisms like Acanthamoeba.
Treatment Approaches
Treatment approaches vary depending on the identified cause of the keratitis.
Bacterial Infections: Topical antibiotic eye drops are the primary treatment, with frequency ranging from several times a day to every 30 minutes in severe cases. Oral antibiotics may be used as a supplement in some situations.
Viral Infections: Managed with antiviral eye drops and sometimes oral antiviral medications.
Fungal Infections: Usually require both topical antifungal eye drops and oral antifungal medications, which can be a lengthy course of treatment.
Parasitic Infections (Acanthamoeba): This type is particularly challenging to treat and often involves specific antiparasitic eye drops, such as polyhexamethylene biguanide (PHMB) or chlorhexidine, for several months due to the parasite’s resistant cyst form.
If medical treatment is unsuccessful or causes significant permanent corneal damage, a cornea transplant may be necessary to restore vision. Prompt diagnosis and strict adherence to the prescribed treatment regimen are of utmost importance to prevent severe vision loss and other complications.
Preventing Future Infections
Prevention focuses on maintaining good eye hygiene and protecting the eyes from injury.
Contact Lens Care
For contact lens wearers, proper care is essential. Always wash hands thoroughly with soap and water before handling lenses. Use fresh, sterile contact lens solution each time lenses are stored, and never reuse old solution. Avoid sleeping, napping, or swimming while wearing contact lenses, as these activities significantly increase the risk of infection. Lenses should be replaced according to the recommended schedule from an eye care professional, and contact lens cases should be cleaned regularly and replaced every few months.
General Eye Protection
Wear protective eyewear during activities that could cause eye injury, such as sports or certain occupations. Avoid rubbing the eyes, especially with unwashed hands, to minimize the transfer of microorganisms. Any eye trauma or persistent irritation, even seemingly minor, warrants prompt medical attention to prevent potential infection.