Diabetes Mellitus and Fungal Keratitis: Comparative Aetiological and Diagnostic Profile in a Tertiary Care Ophthalmic Hospital

Background: Fungal keratitis is a major cause of infectious keratitis and corneal blindness in tropical regions, with fungi responsible for 30-40% of cases. Diabetes mellitus increases susceptibility due to impaired epithelial healing, neurotrophic keratopathy, and immune dysfunction. Comparative data on etiological profiles, diagnostic yields, and fungal isolate distribution between diabetic and non-diabetic patients with fungal keratitis remain limited. This study aimed to compare the etiological and diagnostic profiles of fungal keratitis in patients with and without diabetes mellitus at a tertiary care ophthalmic hospital in Hyderabad, India.

Materials &Methods: This prospective observational study enrolled 100 consecutive patients with clinical features suggestive of infectious keratitis: 50 with diabetes mellitus (past 5 years) and 50 non-diabetic controls. Exclusion criteria included bacterial, viral, or parasitic keratitis and prior antifungal therapy. Corneal scrapings were collected from the ulcer base and advancing edge under topical anesthesia. Samples underwent direct microscopy (10% KOH mount), Gram staining, and culture on blood agar, chocolate agar, and Sabouraud dextrose agar (SDA) (25°C, up to 4 weeks). Fungal isolates were identified by colony morphology and lactophenol cotton blue (LPCB) mounts. Data were analyzed using descriptive statistics and chi-square test (p < 0.05 significant). Ethical clearance and informed consent were obtained.

Results: Diabetic patients were significantly older (74% >50 years; p = 0.000005) than non-diabetics (majority 30–49 years), with male predominance in both groups (64% vs. 70%). Trauma was the leading risk factor overall (32-40%), alongside foreign body exposure. Agricultural workers predominated (44% diabetics, 38% non-diabetics). Fungal culture positivity was 54% in diabetics and 50% in non-diabetics (overall 52%). KOH mount positivity was higher in diabetics (50%) than non-diabetics (34%). Fusarium spp. was the most common isolate in both groups (28% diabetics, 24% non-diabetics), followed by Aspergillus flavus (8% in both), Aspergillus niger (4–8%), Curvularia spp. (4-6%), Aspergillus fumigatus (2%), and unidentified isolates (2–8%). In diabetics, KOH-positive cases showed 23/25 culture-positive results; in non-diabetics, all 17 KOH-positive cases were culture-positive.

Conclusions: Fungal keratitis in diabetic patients showed higher KOH positivity and occurred in older individuals compared to non-diabetics, with Fusarium spp. predominant in both groups, consistent with tropical epidemiology. Diabetes influences diagnostic yield and demographic presentation but not markedly the fungal spectrum. Regional surveillance and prompt microscopy remain essential for diagnosis, while localized data guide empirical therapy amid rising diabetes prevalence. Further molecular studies are recommended for precise species identification and targeted management.