Fungal Keratitis is one of the most difficult forms of
microbial keratitis to diagnose & to treat successfully.
Fungus are eukaryotic heterotrophic organisms &
typically forms reproductive spores.
Fugus may be a part of normal external ocular flora. (
3-28% of normal eyes)
Most commonly seen are:
Overall incidence is low- 6-20%
Aspergillus most common organism
Incidence varies geographically:
Northern US: Candida, Aspergillus
Southern US: Fusarium
In India: Aspergillus (27-64%)
Fungi gain entry into stroma through a defect
in epithelial barrier.
In stroma, cause tissue necrosis & host
Fungus can penetrate deep into stroma &
through intact descemet’s membrane.
Blood borne growth inhibiting factors may not
reach avascular structures of eye like cornea
so fungi continues to grow & persists i.e. why
conjunctival flap help in control of fungal
Foreign body Sensation
Slow onset increasing Pain
Clinical signs are more severe than symptoms.
Nonspecific: Conjunctival injection
Anterior chamber reaction
Gray/Brown Pigmentation( s/o Dematiceous
Fungi like Curvularia)
Hypopyon ( Non Sterile, thick & immobile)
Yellow line of demarcation
Immune Ring (Wesseley)
Grocott’s Methamine Silver
Smear: Potassium Hydroxide Wet Mount
Should include same media for general infectious
keratitis work up.
Sheep Blood Agar
Sabouraud’s dextrose Agar
Brain Heart Infusion Broth / Solid Media
Positive culture expected in 90% cases,
within 72 hrs in 83% cases
within 1 week in 97% cases
Increasing Humidity of medium by placing inoculated
agar plates in Plastic bags enhance fungal growth.
Polymerase Chain Reaction
Provide initial debridement of organisms
Improve penetration of drugs
Diamond tipped motorized burr
Diagnostic Superficial Keratectomy/Corneal
Done in Minor OT with Topical Anaesthesia
2-3 mm dermatologic trephine on anterior
corneal stroma incorporating both clinically
infected & adjacent clear cornea.(Avoiding
27 guage hypodermic needle
6-0 silk suture
Anterior Chamber Tap:
Hypopyon or Endothelial Plaque
Amphotericin B, Natamycin
Binds to ergosterol in fungal cell membrane &
cause the membrane to become leaky.
Inhibits CYP P450 14 a-demethylase enzyme
involved in conversion of lanosterol to
Topical Natamycin 5% is Initial drug of choice.
Topical Amphotericin B 0.15% added in c/o
worsening, candida & aspergillus.
Oral or Topical Azole added in c/o Fusarium.
Indication for Systemic antifungals:
( voriconazole 1st choice)
Severe deep keratitis
Prophylactic t/t after Penetrating Keratoplasty
for Fungal Keratitis
Length of treatment is based on clinical
response of individual.
If toxicity is suspected and if adequate t/t has
been given for 4-6 weeks treatment should be
discontinued & patient is observed for
reccurence in follow up.
Intrastromal injections: given if infiltrate is
recalcitrant to topical t/t & depth of lesion in
Subconjunctival injections: reserved in cases
of scleritis, severe keratitis, endophthalmitis.
Miconazole (preferred) as is least toxic
Done every 24-48 hrs under topical anaesthesia
Debulks necrotic material & organisms
Enhances penetration of topical drugs
Infectious process progress to limbus or sclera
Failure of medical t/t
Recurrence of infection
To delay or prevent the need for corneal transplant with
severe thinning or perforation is managed with
TISSUE ADHESIVE(N-BUTYL CYANOACRYLATE)
BANDAGE CONTACT LENS
Technique for Penetrating Keratoplasty:
Size of trephination should leave 1-1.5 mm
clear zone of clinically uninvolved cornea to
reduce residual fungus.
Interrupted sutures with slight longer bites
Should be used to avoid cheese wiring
Irrigation of Anterior chamber with
Affected intraocular structures like iris, lens,&
vitreous should be excised
Surgical instruments should be changed to
sterile ones once infected tissue removed to
If endophthalmitis is suspected:
Intraocular Antifungal injected at the time of
keratoplasty. ( Preferably Amphotericin B)
Topical antifungals continued to prevent recurrence.
If pathology reports are negative for organism at
edge of corneal specimen STOP antifungals after 2
weeks and follow up patient for recurrence.
If Pathology reports are positive t/t continued for 6-8
CICLOSPORIN A: Antifungal that also prevent
immune response so can be used in place of steroids
Factors associated with Treatment Failure:
Large ulcer size (greater than 14mm square)
Presence of Hypopyon
Aspergillus as causative organism