Aetiology
Herpes simplex (disciform keratitis – relatively frequent complication of herpes simplex keratitis
Herpes zoster (less frequent)
Cytomegolovirus (Ophthalmology 2008;115:292-297) (rare – probably)
Idiopathic – cause unknown

Findings
Localised central or eccentric corneal oedema with keratic preciptitates
In CMV, there appear to be a line of keratic precipitates on the leading edge of the posterior surface of the oedematous cornea with coin-shapped lesions on the corneal endothelial surface within the main body of oedematous cornea.

Diagnosis
Clinical
Aqueous humour tested by PCR

Treatment
Most patients will respond to steroids +/-  systemic acyclovir if herpes simplex is suspected. Non-responsive patients might benefit from aqueous humour tap and PCR to determine whether systemic ganciclovir treatment is warranted. CMV endotheliitis has only recently been reported.