Fungal keratitis

A fungal keratitis is an 'inflammation of the eye's cornea' (called keratitis) that results from infection by a fungal organism. Keratomycosis is the latin terminology equivalent of fungal keratitis - it is the fungal infection of the cornea, the anterior part of the eye which covers the pupil. Those experiencing these symptoms are typically advised to immediately visit the appropriate eyecare professional.

Classification
Infectious keratitis can be bacterial, fungal or viral. Remarkable differences in presentation of the patient allows presumptive diagnosis by the eye care professional, helping in institution of appropriate anti-infective therapy.

Signs and symptoms
The symptoms of fungal keratitis are blurred vision, a red and painful eye that does not improve when contact lenses are removed, increased sensitivity to light, and excessive tearing or discharge. The slit lamp examination shows a corneal ulcer with satellite lesions in the surrounding cornea. There can be associated hypopyon and may even extend to the posterior segment to cause endophthalmitis in later stages, leading to the destruction of the eye.

Causes
Filamentous fungi Yeasts
 * Aspergillus fumigatus
 * Fusarium spp.
 * Candida

Pathophysiology
The precipitating event for fungal keratitis is trauma with a vegetable / organic matter. A thorn injury, or in agriculture workers, trauma with a wheat plant while cutting the harvest is typical. This implants the fungus directly in the cornea. The fungus grows slowly in the cornea and proliferates to involve the anterior and posterior stromal layers. The fungus can break through the descemet's membrane and pass into the anterior chamber. The patient presents a few days or weeks later with fungal keratitis.

Diagnosis
The diagnosis is made by an ophthalmologist correlating typical history, symptoms and signs. A definitive diagnosis is established only after a positive culture report, typically taking a week, from the corneal scraping. Recent advances have been made in PCR / immunologic tests which can a give a much quicker result.

Treatment and management
A presumptive diagnosis of fungal keratitis requires immediate empirical therapy. Natamycin ophthalmic suspension is the drug of choice for filamentous fungal infection. Fluconazole ophthalmic solution is recommended for Candida infection of the cornea. Amphotericin B eye drops may be required for non-responding cases, but can be quite toxic and requires expert pharmacist for preparation. Other medications have also been tried with moderate success.

Prognosis
The infection typically takes a long time to heal, since the fungus itself is slow growing. Corneal perforation can occur in patients with untreated or partially treated infectious keratitis and requires surgical intervention in the form of corneal transplantation.

Prevention/Screening
Prevention of trauma with vegetable / organic matter, particularly in agricultural workers while harvesting can reduce the incidence of fungal keratitis. Wearing of broad protective glasses with side shields is recommended for people at risk for such injuries.

Epidemiology
This disease is quite common in the tropics and with large agrarian population. India has a high number of cases with fungal keratitis, but poor reporting system prevents accurate data collection. Florida in US regularly reports cases of fungal keratitis, with Aspergillus and Fusarium spp. as the most common causes.

Social impact
The loss of vision with fungal keratitis can be quite disabling in terms of economic impact and social consequences. Many people come with fungal keratitis in the only eye and thus become blind due to the disease. The lack of education and proper eye protection in such cases is evidently responsible for their plight.

Notable cases
Recently, one particular product, ReNu with MoistureLoc® brand of soft contact lens solutions made headlines regarding a report from the United States Centers for Disease Control and Prevention suggesting an increased incidence of a specific type of fungal keratitis (Fusarium keratitis) in people using Bausch & Lomb products. Bausch & Lomb subsequently suspended, then recalled, shipments of one particular product, ReNu with MoistureLoc®.