Fungal keratitis is a

fungal infection Fungal infection, also known as mycosis, is a 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 ...

of the

cornea The cornea is the transparency (optics), transparent front part of the eyeball which covers the Iris (anatomy), iris, pupil, and Anterior chamber of eyeball, anterior chamber. Along with the anterior chamber and Lens (anatomy), lens, the cornea ...

, which can lead to

blindness Visual or vision impairment (VI or VIP) is the partial or total inability of visual perception. In the absence of treatment such as corrective eyewear, assistive devices, and medical treatment, visual impairment may cause the individual difficul ...

. 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 pressur ...

. 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 s ...

'', ''

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, Miche ...

'' or ''

Candida Candida, or Cándida (Spanish), may refer to: Biology and medicine * ''Candida'' (fungus), a genus of yeasts ** Candidiasis, an infection by ''Candida'' organisms * Malvasia Candida, a variety of grape Places * Candida, Campania, a ''comu ...

''. Up to 70 different

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

have been found as causes. Fungal keratitis has a worldwide distribution, but is more common in the

tropics The tropics are the regions of Earth surrounding the equator, where the sun may shine directly overhead. This contrasts with the temperate or polar regions of Earth, where the Sun can never be directly overhead. This is because of Earth's ax ...

. Around 1 million people become blind every year due to fungal keratitis. Theodor Leber 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 Inflammation#Cellular component, inflammatory cells in the anterior chamber of the human eye, eye. It is an exudate rich in white blood cells, seen in the anterior chamber, usually accompanied by redness ...

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

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

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

is extremely rare)

Causes

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

, of which ''

'', ''

'' and ''

'' 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 Hyphomycetes, hyphomycete (Mold (fungus), mold) fungus, 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 tropica ...

'' 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 p ...

''. '' C. albicans'', '' C. guilliermondii'' and '' C. parapsilosis'' are the main types of ''

'' to cause fungal keratitis. Other fungus causes; such as ''Phaeoisaria clematidis'' was found in 2000. Then ''Pleurothecium recurvatum'' (formerly ''Carpoligna pleurothecii'') was found in 2010.

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 Natamycin, also known as pimaricin, is an antifungal medication used to treat fungal infections around the eye. This includes infections of the eyelids, conjunctiva, and cornea. It is used as eyedrops. Natamycin is also used in the food in ...

ophthalmic suspension is the drug of choice for filamentous fungal infection.

Fluconazole Fluconazole is an antifungal medication used for a number of fungal infections. These include candidiasis, blastomycosis, coccidioidomycosis, cryptococcosis, histoplasmosis, dermatophytosis, and tinea versicolor. It is also used to pr ...

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 cryptococ ...

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, 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 by population (United Nations), most populous country since ...

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 Theodor Leber 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 Contact lenses, or simply contacts, are thin lens (optics), lenses placed directly on the surface of the Human eye, eyes. Contact lenses are ocular prosthetic devices used by over 150 million people worldwide, and they can be worn to correct ...

solutions made headlines regarding a report from the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

Centers for Disease Control and Prevention The Centers for Disease Control and Prevention (CDC) is the National public health institutes, national public health agency of the United States. It is a Federal agencies of the United States, United States federal agency under the United S ...

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

'' keratitis) in people using

Bausch & Lomb Bausch & Lomb (since 2010 stylized as Bausch + Lomb) is an American-Canadian 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, intra ...

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