Journal of Ophthalmology & Clinical Research Category: Clinical Type: Research Article
Fungal Keratitis - A Brief Overview
- Shalini Malhotra1*, Shweta Sharma1, Nirmaljit Kaur1, Charoo Hans1
- 1 Dr Ram Manohar Lohia Hospital, PGIMER, New Delhi, India
*Corresponding Author:Shalini Malhotra
Dr Ram Manohar Lohia Hospital, PGIMER, New Delhi, India
Received Date: Sep 17, 2015 Accepted Date: Dec 15, 2015 Published Date: Dec 29, 2015
EPIDEMIOLOGY OF FUNGAL KERATITIS
It is seen that there is preponderance of filamentous fungi in tropical areas while temperate climates show higher percentages of yeast infections [12,13].
- Trauma to the eye with vegetative matter is the most common predisposing factor. Trauma could predispose to ulcerative keratitis in 23-55% of cases as per the incidence predicted in various studies . A typical history of young adult engaged in agricultural or outdoor work gets trauma with vegetative matter and develops an ulcerative lesion in 10-15 days is seen in cases of fungal keratitis. The peak months of disease correspond to harvesting season, when chances of injury with infected vegetative matter are very high.
- Environmental factors like humidity, rainfall and wind greatly influence the occurrence of filamentous fungal keratitis .
- Contact lens overuse especially with hydrogel contact lenses .
- Corneal surgery such as penetrating keratoplasty, clear cornea (sutureless) cataract surgery, photorefractive keratectomy, or Laser In Situ Keratomileusis (LASIK) .
- Chronic Keratitis due to herpes simplex, herpes zoster, or vernal keratoconjunctivitis .
- Long term topical medications like corticosteroids and antibiotics [13,16].
- Allergic conjunctivitis due to airborne or bacterial toxins in tears or chemical agents causing injury to eye .
- Long term illnesses like diabetes, atopic diseases, cancer, long term systemic steroids or cytotoxic drugs .
- Pre-existing ocular conditions namely insufficient tear secretion, defective eyelid closure etc., [16,17].
|Hyaline hyphomycetes||Aspergillus||A. fumigatus, A. flavus|
|Fusarium||F. solani, F. oxysporum|
|Acremonium||A. potronii, A. kiliense|
|Penicillium||P. spinulosum, P. citrinum|
|Paecilomyces||P. lilacinus, P. variotii|
|Zygomycetes (rarely)||Absidia, Rhizopus|
|Phaeoid hyphomycetes||Curvularia||C. lunata, C. geniculata, C. senegalensis|
|Bipolaris||B. spicifera, B. hawaiiensis|
|Exserohilum||E. rostratum, E. longirostrata|
|Yeast like fungi||Candida||C. albicans, C. tropicalis, C. krusei|
|Trichosporon, Rhodotorula, Saccharomyces||Rarely seen|
|Dimorphic fungi||Histoplasma, Blastomyces, Cryptococcus||Very rare|
Pathogenesis of fungal keratitis [8-10]
DIAGNOSIS OF FUNGAL KERATITIS
Processing of samples
Other laboratory tests
Molecular methods like Polymerase Chain Reaction (PCR) assay, RT-PCR (Real Time PCR), PCRSSCP (Single Stranded Conformational Polymorphism) and PCR-RFLP (Restriction Fragment Length Polymorphism) techniques have also been standardized for fungal identification . Of these, PCR is most commonly used for diagnosing fungal keratitis because it offers increased sensitivity and significant reduction in the time required to establish a diagnosis. Its sensitivity ranges between 89 to 94%, whereas, specificity ranged between 50% to 88% [35,36]. It can detect fungal DNA for the majority of fungal corneal ulcers with negative culture, and by using the DNA sequencing or specific primers, novel organisms can be detected in culture-negative cases . Real time PCR can also quantify the load of the organism and can be used in the treatment follow up. However, there are certain limitations with molecular methods such as differentiating between active and latent infections, viable and nonviable organisms especially after treatment, cost and false positive results may also occur during the DNA sequencing due to contamination .
TREATMENT OF FUNGAL KERATITIS
If corneal infection progresses inspite of vigorous antifungal therapy or in patients with impending perforation with presence of a descemetocele, surgical debridement like penetrating keratoplasty (full thickness corneal grafting) is done . In this procedure, at least 0.5 mm of clear corneal tissue is excised all around the infected area in order to decrease the chances of recurrence. In some cases where infection does not extend through the entire thickness of the cornea, lamellar keratoplasty can be considered . Hypopyon, corneal perforation, corneal infection extending to limbus, or lens infection are major risk factors for recurrence of infection . Table 2, is highlighting the management protocol of fungal keratitis.
|Superficial keratitis||1stchoice||Natamycin 5% ointment|
|2ndchoice||Amphotericin B 0.15% drops|
|Deep keratitis||Oral itraconazole or fluconazole along with topical therapy|
|Yeast like fungi|
|Superficial keratitis||1stchoice||Amphotericin B 0.15% drops|
|2ndchoice||fluconazole 2%/itraconazole 1%/voriconazole 1% drops|
|Deep keratitis||Oral itraconazole or fluconazole along with topical therapy|
|Non-responders or presence of descemetocele||Penetrating keratoplasty along with topical and systemic antifungals|
Newer modality of treatment
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Citation:Malhotra S, Sharma S, Kaur N, Hans C (2015) Fungal Keratitis- A Brief Overview. J Ophthalmic Clin Res 2: 018.
Copyright: © 2015 Shalini Malhotra, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.