Acanthamoeba keratitis is a rare and severe eye infection that can lead to permanent vision loss. The condition is caused by Acanthamoeba, a single-cell organism commonly found in water and soil. Approximately 85% to 95% of individuals infected wear contact lenses.
Infection Mechanism
Acanthamoeba can adhere to the cornea's surface. Breaks in the corneal epithelium, the eye's protective outer layer, allow the parasite to burrow into the cornea. Contact lenses can create these abrasions, or the amoeba can become trapped between the lens and the eye, facilitating deeper penetration. The parasite uses the cornea as a food source, causing inflammation, tissue damage, and potential vision loss.
Diagnosis Challenges
Early diagnosis of acanthamoeba keratitis presents difficulties due to several factors:
- Rarity: Many optometrists may not be familiar with the condition.
- Symptom Mimicry: Symptoms such as pain, light sensitivity, obscured vision, redness, dryness, excessive tears, and a foreign body sensation can resemble other corneal infections, including herpes simplex keratitis or pink eye.
- Misdiagnosis: Initial misdiagnoses are common, leading to ineffective or harmful treatments that can worsen the condition while the parasite continues to damage the cornea.
Diagnostic methods include corneal scrapings, swabbing, or biopsies for lab processing (culturing or PCR tests). Confocal microscopy can identify the amoeba in the cornea when it forms cysts. These specialized tests and specialists are not universally available.
Treatment and Outcomes
Treatment for acanthamoeba keratitis is prolonged, often lasting months to years, and can be challenging due to the parasite's resilience. First-line treatments involve anti-amoebic eye drops like chlorhexidine, propamidine isethionate, hexamidine, or PHMB. Some drops can cause intense pain and require frequent application, sometimes every half hour or hour, for extended periods.
In cases of significant corneal scarring, thinning, or perforation, a cornea transplant may be necessary. However, the parasite can lie dormant for years and reactivate, posing a risk to a new cornea. Doctors typically ensure sufficient healing time without treatment before a transplant. Some patients experience significant vision improvement, potentially reaching 20/20, while others may have persistent vision impairment.
Prevention
Experts recommend several practices to reduce the risk of acanthamoeba keratitis:
- Use only store-bought or prescription contact lens solution for cleaning and storing contacts.
- Change the solution in the contact lens case daily.
- Wash and dry hands thoroughly before handling contacts.
- Avoid wearing contact lenses while sleeping, showering, or swimming.
- Consider daily disposable contacts as a lower-risk alternative to monthly lenses.
- Explore vision correction surgeries (e.g., LASIK, PRK, Smile, EVO ICL) as an alternative to contact lens use.
Patient Experience and Support
Individuals who have experienced acanthamoeba keratitis often emphasize the importance of trusting medical professionals, practicing patience throughout treatment, and seeking support from online communities. Early recognition of symptoms and prompt consultation with a cornea specialist are crucial for improving outcomes.