¡¡¡¡DISCUSSION

¡¡¡¡Fungal keratitis becomes a diagnostic and therapeutic challenge to ophthalmologist. The problems are related to obtaining a clinical diagnosis, isolating the etiology fungal organism by laboratory investigation and treating the keratitis effectively with available current topical antifungal. The contributing factors for development of fungal infection are ocular trauma, contamination of corneal lesion by soil and plant material, and the frequent use of topical costicoª²steroid [1ª²3]. Fungal keratitis is surprisingly rarely reported among the contact lens users (Table 1). Most of the studies done on fungal keratitis showed trauma is the commonest risk factor (Table 1).

¡¡¡¡Most of contact lens related keratitis is caused by pseudomonas aeruginosa followed by gram positive bacteria, other gram negative bacteria, acanthamoeba sp and less likely by fungi (Table 1). Among fungal keratitis, the filamentous type is the commonest cause of mycotic keratitis in many countries in tropical latitudes[9]. However, in more temperate climates, fungal ulcers are uncommon and candida species are more frequently isolated compared to filamentous fungi [8]. Lane 1:100bp plus marke
Lane 2&8:Fungus, Positive control neat DNA
Lane 3&9:Fungus, Positive control 1/10 DNA
Lane 4&10:Patient neat DNA sample (1st sample)
Lane 5&11:Patient neat DNA sample (2nd sample)
Lane 6&12:Negative control
Lane 7&13:100bp plus marker

¡¡¡¡Corneal epithelial defect usually results from trauma, contact lens wear, and foreign body[2]. Fungi can penetrate into corneal surface, multiply and cause tissue necrosis[2]. Fusarium sp is able to penetrate Descemet¬ðs membrane and gain access to the anterior chamber or the posterior segment of eye[2]. Fusarium sp has ability to secrete proteolytic enzyme that augments the tissue damage. Other factors that may influence soft lens infiltration by fungi are lens material properties, which provide a matrix and nutrient source for fungal growth. Clinically fungal keratitis is suspected when the ulcer is raised, dry, necrotic slough present and satellite lesion seen[10].  An immune ring is also believed to be a frequent occurrence in filamentous fungal keratitis[10]. Regarding the diagnosis, although a detailed clinical examination may help to reach a rapid presumptive diagnosis but fungal keratitis continues to be confused with other causes of inflammatory keratitis[10]. Even though certain clinical characteristics of corneal ulcer may suggest a specific pathogen but a reliable diagnosis cannot be made by clinical appearance alone.As a result, microbiological investigation should be performed.However,the traditional diagnostic laboratory methods including microscopy and culture may be negative despite a clear clinical presentation of suppurative keratitis[9]. It was found that multiplex polymerase chain reaction is of great value for rapid and definite diagnosis of fungal keratitis[11].

¡¡¡¡Refractory fungal keratitis possesses a therapeutic challenge as it may progress to corneal perforation and fungal endophthalª²mitis[12].To arrest infection progression, avoid disastrous complication and preserve the globe integrity, therapeutic penetrating keratoplasty has been advocated for severe fungal keratitis [1,12]. Many studies found that fungal keratitis was the leading indication for therapeutic penetrating keratoplasty for microbial keratitis [1]. Many studies advocate performing surgery early without delaying until after antifungal therapy failed [1,12].

¡¡¡¡In our patient, we were having dilemma in managing her contact lens related corneal ulcer with a negative corneal scrapping culture. She was treated initially as presumed fungal keratitis based on the clinical judgment and was treated with broad spectrum antibiotic and topical as well as systemic antifungal. Unfortunately, her ulcer did not show a good clinical response and even deteriorated with medical treatment, so finally therapeutic penetrating keratoplasty was performed. Corneal button was sent to isolate the organism. Only histopathological examination and polymerase chain reaction (PCR) from corneal button revealed fusarium sp but culture result was still negative.

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  ¡¡1 Xie L, Dong X, Shi W. Treatment of fungal keratitis by penetrating keratoplasty. Br J Ophthalmol 2001;85(9):1070ª²1074

¡¡¡¡2 Alexandrakis G. Fungal keratitis. eMedicine2005; http://www.emedicine.com/oph/topic99.htm

¡¡¡¡3 Yang HY, Suo JJ, Chen SP, Xing YB, Jia N, Song PR. Pathogenic analysis of 13 cases of ocular fungal infection. Int J Ophthalmol(Guoji
Yanke Zazhi) 2003;3(4):125ª²126

¡¡¡¡4 Sharma S,Gopalakrishnan S,Aasuri MK,Garg P,Rao GN.Trend in contact lensª²associated microbial keratitis in southern India. Ophthalmology 2003;110(1):138ª²143

¡¡¡¡5 Alfonso E, Mandelbaum S, Fox MJ, Forster RK. Ulcerative keratitis associated with contact lens wear. Am J Ophthalmol 1986;101(4):429ª²433

¡¡¡¡6 Rosa RH Jr, Miller D, Alfonso EC. The changing spectrum of fungal keratitis in south Florida. Ophthalmology 1994;101(6):1005ª²1013

¡¡¡¡7 Tanure MA, Cohen EJ, Sudesh S, Rapuano CJ, Laibson PR. Spectrum of fungal keratitis at Wills Eye Hospital, Philadelphia, Pennsylvania. Cornea 2000;19(3):307ª²312

¡¡¡¡8 Barr JT. Contact Lens Spectrum¬ðs annual report of major corporate and product developments and events in the contact lens industry in 2004, as well as predictions for 2005. Contact Lens Spectrum 2005; http://www.clspectrum.com/article.aspx?article=12733

¡¡¡¡9 Leck AK,Thomas PA,Hagan M,Kaliamurthy J,Ackuaku E,John M,Newman MJ,Codjoe FS,Opintan JA,Kalavathy CM,Essuman V,Jesudasan CA,Johnson GJ.Aetiology of suppurative corneal ulcers in Ghana and south India, and epidemiology of fungal keratitis. Br J Ophthalmol 2002;86(11):1211ª²1215

¡¡¡¡10 Thomas PA, Leck AK, Myatt M. Characteristic clinical features as an aid to the diagnosis of suppurative keratitis caused by filamentous fungi. Br J Ophthalmol 2005;89(12):1554ª²1558

¡¡¡¡11 Lu H,Guan HJ.Rapid diagnosis of HSK and fungal keratitis using multiplex polymerase chain reaction. Int J Ophthalmol(Guoji Yanke Zazhi) 2004;4(4):657ª²660

¡¡¡¡12 Yao YF, Zhang YM, Zhou P, Zhang B, Qiu WY, Tseng SC. Therapeutic penetrating keratoplasty in severe fungal keratitis using cryopreserved donor corneas. Br J Ophthalmol 2003;87(5);543ª²547

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