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fungal infection of the cornea

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2014/07/18 22:12:04」(JST)

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A fungal keratitis is an 'inflammation of the eye's cornea' (called keratitis) that results from infection by a fungal organism. Keratomycosis is the Greek 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, 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.

Clinical features

The symptoms of fungal keratitis are blurred vision, a red and painful eye that does not improve when contact lenses are removed, or on antibiotic treatment, increased sensitivity to light(photophobia), and excessive tearing or discharge. The symptoms are markedly less as compared to a similar bacterial ulcer. Signs: The eyelids and adnexa involved shows edema and redness, conjuctiva 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 which is mostly white fluffy in appearance. Rarely, it may extend to the posterior segment to cause endophthalmitis in later stages, leading to the destruction of the eye. (Note: Fungal endophthalmitis is extremely rare)

Causes

Filamentous fungi

Aspergillus flavus
Aspergillus fumigatus
Fusarium spp.
Alternaria spp.

Yeasts

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/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 / immunologic tests which can 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. Consult your eye care professional in any case as they will have the best treatment.

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.^[1] Bausch & Lomb subsequently suspended, then recalled, shipments of one particular product, ReNu with MoistureLoc.^[2]

References

^ "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 News". Bausch & Lomb. Retrieved. June 2, 2006.

External links

mycotic keratitis

UpToDate Contents

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English Journal

Clinical utility of caspofungin eye drops in fungal keratitis.

Neoh CF1, Daniell M2, Chen SC3, Stewart K4, Kong DC5.
International journal of antimicrobial agents.Int J Antimicrob Agents.2014 Aug;44(2):96-104. doi: 10.1016/j.ijantimicag.2014.04.008. Epub 2014 May 17.
Treatment of fungal keratitis remains challenging. To date, only the polyenes and azoles are commonly used topically in the management of fungal keratitis. Natamycin, a polyene, is the only antifungal eye drop that is commercially available; the remainder are prepared in-house and are used in an 'of
PMID 24933448

Clinico-demographical profile of keratomycosis in Delhi, North India.

Gupta A, Capoor MR1, Gupta S, Kochhar S, Tomer A, Gupta V.
Indian journal of medical microbiology.Indian J Med Microbiol.2014 Jul-Sep;32(3):310-4. doi: 10.4103/0255-0857.136582.
This study was undertaken to evaluate the clinico-demographical profile of keratomycosis. (January 2004 to January 2012). The corneal scrapings were processed by direct microscopic methods and standard culture techniques. Of 209 cases of keratitis studied, culture yielded growth in 80 cases (38.3%).
PMID 25008827

Evaluation of the conjunctival fungal flora and its susceptibility to antifungal agents in healthy horses in Switzerland.

Voelter-Ratson K1, Monod M, Unger L, Spiess BM, Pot SA.
Veterinary ophthalmology.Vet Ophthalmol.2014 Jul;17 Suppl 1:31-6. doi: 10.1111/vop.12088. Epub 2013 Aug 2.
OBJECTIVE: To characterize the conjunctival fungal flora and to determine the susceptibility of 2 isolated molds to antifungal drugs in samples of 64 healthy horses from The National Stud in Switzerland.PROCEDURE: Conjunctival cytobrush samples were collected from both eyes of 64 ophthalmologically
PMID 23910390