Classification of Corneal Ulcers On The Basis Of Aetiology

Microbial ulcers
These are caused by Staph or Strep species, present with pain, redness, lid
oedema and discharge that varies according to the duration and severity of the
ulcer. The ulcer is well circumscribed and may be central or at mid-periphery of
the cornea. The borders of the ulcer are usually round or oval. Stromal infiltration
may be present under the base of the ulcer with a yellowish white appearance.
In severe ulcers, there may be folds in the deep stroma radiating from the ulcer
bed; additionally a levelled hypopyon, 3 to 4 + cells and flare may be seen.
Rarely posterior corneal abscess may be present with intact epithelium.
Pneumococcal ulcer:
May be associated with chronic dacryocystitis in 55% of cases.
Haemorrhagic hypopyon may be associated with pneumococcal ulcer.
Frequently seen in corneas having degeneration, epithelial problem and
scars.
The creeping edges and dense infiltrate at the leading edge of the ulcer
are characteristic clinical features of pneumococcal ulcer.
Gram positive bacterial ulcers
The uninvolved portion of cornea will appear clear without oedema or infiltration.
Gram negative bacterial ulcer
Pseudomonas ulcer will have a short history.
Signs and symptoms will be severe
Diffuse ulceration with stromal infiltrate or oedema involving adjacent or
whole cornea resulting in ground glass appearance is a distinguishing
clinical feature from other ulcers. Mucopurulent discharge is seen
frequently and it appears bluish green in untreated severe pseudomonas
ulcers.
Marked lid oedema and chemosis than seen in Gram positive bacterial
ulcers.
The ulcer perforates within few days if not managed properly.
Pseudomonas ulcer may develop as ring abscess without epithelial defect.
Ulcer caused by gram negative cocci
Marked lid oedema and copious purulent discharge;
Pus will spurt out when the lids are separated.
Ulcer is usually bilateral and perforates within short duration.
Lid abnormalities like ectropion, entropion, trichiasis, improper closure of lids
as in leprosy, neurotrophic lesions due to herpes simplex, zoster or corneal
degenerations, bullous keratopathy, and dry eyes predispose to bacterial ulcer
in the SEA Region.
Satellite lesions, immune ring, endothelial plaques are present in both
bacterial and fungal keratitis and do not help to differentiate between
bacterial and fungal keratitis.
Fungal Keratitis
The ulcer usually involves the central or exposed part of cornea.
The edges are feathery with finger like projections, mimicking a herpetic
dendritic ulcer in early stages.
The fungal ulcer has raised creamy surface with greyish white infiltrate;
The base of the ulcer is dry leathery (not in early fungal ulcer of about
one week duration).
The hypopyon is unlevelled and solid.
There may be posterior corneal abscess with intact corneal epithelium.
The remaining cornea appears clear.
Pigmented fungal ulcer
The surface will show brown or dark pigmentation which is tough and
leathery;
Very difficult to scrape for diagnostic or therapeutic purposes.
Untreated or improperly treated ulcer may progress to involve sclera also.
Fungal ulcer caused by Candida
Usually involves an immunocompromised host and cornea;
The ulcer appears as collar button and mimics staphylococcal ulcer.