Fungal keratitis is a

fungal infection Fungal infection, also known as mycosis, is disease caused by fungi. Different types are traditionally divided according to the part of the body affected; superficial, subcutaneous, and systemic. Superficial fungal infections include common ti ...

of the

cornea The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Along with the anterior chamber and lens, the cornea refracts light, accounting for approximately two-thirds of the eye's total optical ...

, which can lead to

blindness Visual impairment, also known as vision impairment, is a medical definition primarily measured based on an individual's better eye visual acuity; in the absence of treatment such as correctable eyewear, assistive devices, and medical treatment� ...

. It generally presents with a red, painful eye and

blurred vision Blurred vision is an ocular symptom where vision becomes less precise and there is added difficulty to resolve fine details. Temporary blurred vision may involve dry eyes, eye infections, alcohol poisoning, hypoglycemia, or low blood pressure ...

. There is also increased sensitivity to light, and excessive tears or discharge. It is caused by fungal organisms such as ''

Fusarium ''Fusarium'' is a large genus of filamentous fungi, part of a group often referred to as hyphomycetes, widely distributed in soil and associated with plants. Most species are harmless saprobes, and are relatively abundant members of the soil mi ...

'', ''

Aspergillus ' () is a genus consisting of several hundred mold species found in various climates worldwide. ''Aspergillus'' was first catalogued in 1729 by the Italian priest and biologist Pier Antonio Micheli. Viewing the fungi under a microscope, Mic ...

'' or '' Candida''. Fungal keratitis has a worldwide distribution, but is more common in the

tropics The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also refer ...

. Around 1 million people become blind every year due to fungal keratitis.

Theodor Leber Theodor Karl Gustav von Leber (29 February 1840 – 17 April 1917) was a German ophthalmologist from Karlsruhe. Leber was a student of Hermann von Helmholtz (1821-1894) in Heidelberg, where he received his doctorate in 1862. He remained in Hei ...

first described a case of fungal keratitis caused by ''Aspergillus'' in 1879.

Signs and symptoms

The symptoms of fungal keratitis typically emerge over 5-10 days and present with a painful eye, blurred vision, and redness of eye. There is increased sensitivity to light, and excessive tears or discharge. The symptoms are markedly less as compared to a similar bacterial ulcer. Symptoms may be noted to persist after contact lenses are removed, or following antibiotic treatment. Signs: The eyelids and adnexa involved shows edema and redness, conjunctiva is chemosed. Ulcer may be present. It is a dry looking corneal ulcer with satellite lesions in the surrounding cornea. Usually associated with fungal ulcer is

hypopyon Hypopyon is a medical condition involving inflammatory cells in the anterior chamber of the eye. It is an exudate rich in white blood cells, seen in the anterior chamber, usually accompanied by redness of the conjunctiva and the underlying ep ...

, which is mostly white fluffy in appearance. Rarely, it may extend to the

posterior segment The posterior segment or posterior cavity is the back two-thirds of the eye that includes the anterior hyaloid membrane and all of the optical structures behind it: the vitreous humor, retina, choroid, and optic nerve.endophthalmitis Endophthalmitis is inflammation of the interior cavity of the eye, usually caused by infection. It is a possible complication of all intraocular surgeries, particularly cataract surgery, and can result in loss of vision or loss of the eye itself. ...

in later stages, leading to the destruction of the eye. (Note: Fungal

endophthalmitis Endophthalmitis is inflammation of the interior cavity of the eye, usually caused by infection. It is a possible complication of all intraocular surgeries, particularly cataract surgery, and can result in loss of vision or loss of the eye itself. ...

is extremely rare)

Causes

Fungal keratitis has been reported to be caused by more than 70 different

fungi A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately fr ...

, of which ''

'', ''

'' and '' Candida'' are responsible for 95% of cases. '' A. flavus'' and '' A. fumigatus'' are the most common types of ''Aspergillus'' to cause fungal keratitis. '' F. Solani'' is the most common type of ''

'' and others include ''

Curvularia ''Curvularia'' is a genus of hyphomycete (mold) fungi which can be pathogens but also act as beneficial partners of many plant species. They are common in soil. Most ''Curvularia'' species are found in tropical regions, though a few are found in ...

'' and ''

Acremonium ''Acremonium'' is a genus of fungi in the family Hypocreaceae. It used to be known as ''Cephalosporium''. Description ''Acremonium'' species are usually slow-growing and are initially compact and moist. Their hyphae are fine and hyaline, and pro ...

''. '' C. albicans'', '' C. guilliermondii'' and '' C. parapsilosis'' are the main types of '' Candida'' to cause fungal keratitis.

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/optometrist correlating typical history, symptoms and signs. Many times it may be missed and misdiagnosed as bacterial ulcer. A definitive diagnosis is established only after a positive culture report (lactophenol cotton blue, calcoflour medium), typically taking a week, from the corneal scraping. Recent advances have been made in PCR ref 3./immunologic tests which can give a much quicker result.

Classification

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

Prevention

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.

Treatment

A presumptive diagnosis of fungal keratitis requires immediate empirical therapy. Natamycin ophthalmic suspension is the drug of choice for filamentous fungal infection.

Fluconazole Fluconazole is an antifungal medication used for a number of fungal infections. This includes candidiasis, blastomycosis, coccidiodomycosis, cryptococcosis, histoplasmosis, dermatophytosis, and pityriasis versicolor. It is also used to prev ...

ophthalmic solution is recommended for Candida infection of the cornea.

Amphotericin B Amphotericin B is an antifungal medication used for serious fungal infections and leishmaniasis. The fungal infections it is used to treat include mucormycosis, aspergillosis, blastomycosis, candidiasis, coccidioidomycosis, and cryptococcosis ...

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. An updated Cochrane Review published in 2015 looking at the best treatment for fungal keratitis could not draw any conclusions as the studies included used different medications. The review did find that "people receiving natamycin were less likely to develop a hole in their cornea and need a transplant."

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 Corneal transplantation, also known as corneal grafting, is a surgical procedure where a damaged or diseased cornea is replaced by donated corneal tissue (the graft). When the entire cornea is replaced it is known as penetrating keratoplasty a ...

Epidemiology

This disease is quite common in the tropics and with large agrarian population.

India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area, the List of countries and dependencies by population, second-most populous ...

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. According to the Global Action Fund for Fungal Infections, every year there are around 1 million cases of blindness due to fungal keratitis.

History

A case of fungal keratitis caused by ''Aspergillus'' was first described by

in 1879, in a 54 year old farmer who injured his eye.

Society and culture

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 The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...

Centers for Disease Control and Prevention The Centers for Disease Control and Prevention (CDC) is the national public health agency of the United States. It is a United States federal agency, under the Department of Health and Human Services, and is headquartered in Atlanta, Georg ...

suggesting an increased incidence of a specific type of fungal keratitis (''

'' keratitis) in people using

Bausch & Lomb Bausch + Lomb is an eye health products company based in Vaughan, Ontario, Canada. It is one of the world's largest suppliers of contact lenses, lens care products, pharmaceuticals, intraocular lenses, and other eye surgery products. The compan ...

products."''Fusarium'' Keratitis --- Multiple States, 2006."
Centers for Disease Control and Prevention: ''Morbidity and Mortality Weekly Report.'' April 10, 2006 / 55(Dispatch);1-2. Bausch & Lomb subsequently suspended, then recalled, shipments of one particular product, ReNu with MoistureLoc.
Bausch & Lomb. Retrieved. June 2, 2006.

References

External links

{{Eye pathology Disorders of sclera and cornea