Which of the following is not true regarding fungal corneal ulcer: March 2009
Ans. B: Commonly perforates Causative fungi: Filamentry fungi - include- Aspergillus, fusarium, cephalosphorium, curvuluria, penicillium. Yeast - Candida, Cryptococcus Mode of infection: Injury by vegetative materials (Common sufferers are field workers specially in harvesting season) Injury by animal tail Secondary fungal ulcer - is commonly found in immunosuppresed hosts. Patients who are suffering from dry eye, herpetic Keratitis, bullous keratopathy and Post-operative case of keratoplasty Fungi do not infect the cornea easily - they require trauma, immunological compromised state & tissue devitalization. Fungal corneal infections tend to spread deep into the corneal stroma, where the organisms are inaccessible to the usual diagnosis and therapeutic measure. Fungi even may penetrate an intact Descement's membrane into the anterior chamber. Clinical features: Pain Watering - reflex hyperlacrimation Photophobia - Stimulation of nerve ending Redness - Congestion of circum-corneal vessels, Dry eye, grayish white with elevated rolled out margins Feathery figure like extension surround the stroma under intact epithelium, Yellow line demarcation (sterile immune ring) known as Wessley's ring due to deposition of immune complex and inflammatory cell around the ulcer. Multiple small satellite lesions may present around the ulcer Hypopion - Big, thick, immobile, not sterile may be present Perforation - rarely Corneal vascularisation are conspicuously absent. Diagnosis: - Wet KOH - Direct smear immediately fixed with methyl alcohol. - Giemsa stain - Show ghosting of fungal wall and yeast budding is may be noted. - Gomori methanamine Silver technique - Delineate the hyphae as sharp black structure against a pale green background. - Gram stain - fungus can be seen directly - Periodic acid schiff (PAS) - Calco fluor white
Convex hypopyon
Commonly perforates
Hyphate margins
Satellite lesions are seen