Demystifying viral anterior uveitis: A review

A viral aetiology should be suspected when anterior uveitis is accompanied by ocular hypertension, diffuse stellate keratic precipitates or the presence of iris atrophy. The most common viruses associated with anterior uveitis include herpes simplex virus, varicella-zoster virus, cytomegalovirus and rubella virus. They may present as the following: Firstly, granulomatous cluster of small and medium-sized keratic precipitates in Arlt's triangle, with or without corneal scars, suggestive of herpes simplex or varicella-zoster virus infection. Secondly, Posner-Schlossman syndrome with few medium-sized keratic precipitates, minimal anterior chamber cells and extremely high intraocular pressure; this is mainly associated with cytomegalovirus. Thirdly, Fuchs uveitis syndrome, with fine stellate keratic precipitates diffusely distributed over the corneal endothelium, with diffuse iris stromal atrophy but without posterior synechiae, is associated mainly with rubella or cytomegalovirus infection. In rubella, the onset is in the second to third decade. It presents with posterior subcapsular cataract, may have iris heterochromia and often develops vitritis without macular oedema. Cytomegalovirus affects predominantly Asian males in the fifth to seventh decade, the keratic precipitates may be pigmented or appear in coin-like pattern or develop nodular endothelial lesions, but rarely vitritis. Eyes with cytomegalovirus tend to have lower endothelial cell counts than the fellow eye. As their ocular manifestations are variable and may overlap considerably, viral AU can pose a diagnostic dilemma. Thus, quantitative polymerase chain reaction or Goldmann-Witmer coefficient assay from aqueous humour samples are preferred to confirm the aetiology and determine the disease severity as this impacts the treatment.