Fungal Corneal Ulcer

MYCOTIC CORNEAL ULCER
The incidence of suppurative corneal ulcers caused
by fungi has increased in the recent years due to
injudicious use of antibiotics and steroids.
Etiology
1. Causative fungi. The fungi which may cause
corneal infections are :
i. Filamentous fungi e.g., Aspergillus, Fusarium,
Alternaria, Cephalosporium, Curvularia and
Penicillium.
ii. Yeasts e.g., Candida and Cryptococcus.
(The fungi more commonly responsible for mycotic
corneal ulcers are Aspergillus (most common),
Candida and Fusarium).
2. Modes of infection
i. Injury by vegetative material such as crop
leaf, branch of a tree, straw, hay or decaying
vegetable matter. Common sufferers are field
workers especially during harvesting season.
ii. Injury by animal tail is another mode of
infection.
iii. Secondary fungal ulcers are common in
patients who are immunosuppressed
systemically or locally such as patients
suffering from dry eye, herpetic keratitis,
bullous keratopathy or postoperative cases of
keratoplasty.
3. Role of antibiotics and steroids. Antibiotics
disturb the symbiosis between bacteria and fungi;
and the steroids make the fungi facultative pathogens
which are otherwise symbiotic saprophytes.
Therefore, excessive use of these drugs predisposes
the patients to fungal infections.
Clinical features
Symptoms are similar to the central bacterial corneal
ulcer (see page 95), but in general they are less marked
than the equal-sized bacterial ulcer and the overall
course is slow and torpid.
Signs. A typical fungal corneal ulcer has following
salient features (Fig. 5.8):
Corneal ulcer is dry-looking, greyish white, with
elevated rolled out margins.
Delicate feathery finger-like extensions are present
into the surrounding stroma under the intact
epithelium.
A sterile immune ring (yellow line of demarcation)
may be present where fungal antigen and host
antibodies meet.
Multiple, small satellite lesions may be present
around the ulcer.

Usually a big hypopyon is present even if the
ulcer is very small. Unlike bacterial ulcer, the
hypopyon may not be sterile as the fungi can
penetrate into the anterior chamber without
perforation.
Perforation in mycotic ulcer is rare but can occur.
Corneal vascularization is conspicuously absent.
Diagnosis
1. Typical clinical manifestations associated with
history of injury by vegetative material are
diagnostic of a mycotic corneal ulcer.
2. Chronic ulcer worsening in spite of most efficient
treatment should arouse suspicion of mycotic
involvement.
3. Laboratory investigations required for
confirmation, include examination of wet KOH,
Calcofluor white, Gram's and Giemsa- stained films
for fungal hyphae and culture on Sabouraud's
agar medium.
Treatment
I. Specific treatment includes antifungal drugs:
1. Topical antifungal eye drops should be used
for a long period (6 to 8 weeks). These
include :
Natamycin (5%) eye drops
Fluconazol (0.2%) eye drops
Nystatin (3.5%) eye ointment.
For details see page 422.
2. Systemic antifungal drugs may be required for
severe cases of fungal keratitis. Tablet
fluconazole or ketoconazole may be given for
2-3 weeks.
II. Non specific treatment. Non-specific treatment
and general measures are similar to that of bacterial
corneal ulcer (see page 98).
III. Therapeutic penetrating keratoplasty may be
required for unresponsive cases.