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Viral disease of the year: Anterior uveitis

If readers will forgive the pun, the title of the paper to be discussed this time caught my eye. Anterior uveitis is a common condition where inflammation in the anterior chamber of the eye leads to raised intraocular pressure and affects vision if untreated. There may be haemorrhage into a segment of the iris which can progress to segmental atrophy. It is often unilateral initially, but can be bilateral, and becomes chronic in some individuals leading to the complications of glaucoma and cataracts. A viral aetiology may be suspected clinically at the outset in cases of herpes zoster ophthalmicus, likewise for HSV, because of a similar neurotropism and the recognised ability of this virus to involve the cornea causing dendritic ulcers. Sampling the aqueous humour via paracentesis of the anterior chamber of the eye was introduced into clinical practice to confirm the diagnosis through detection of VZV or HSV DNA by PCR even in cases lacking overt clinical signs. By employing multiplex PCR for diagnosis, laboratories unexpectedly detected CMV DNA in additional cases. One study used the WHO international standard to quantify viral loads in the small amount (0.1 mL) of aqueous humour available. The median CMV viral load was 4.1 log IU/mL which was about one log lower than found in vitreal fluid from cases of CMV retinitis. The detection of CMV was expected in cases of retinitis in the immunocompromised but was unexpected in immunocompetent individuals who had no clinical features to distinguish their anterior uveitis from cases labelled idiopathic. Patients reported so far are frequently of Asian origin, but it is not clear if this represents a genetic predisposition or more invasive diagnosis of anterior uveitis in some countries. It is assumed that CMV reaches the eye by way of viraemia, rather than through a neural pathway, but with no direct evidence to support this. It seems that the ability to provide an aetiology for many cases that were previously termed idiopathic led our colleagues in ophthalmology to designate anterior uveitis as their viral disease of the year. The possibility that herpesviruses might be found frequently in aqueous humour without inflammation was excluded in a natural history study of patients undergoing cataract surgery where multiplex PCR gave consistently negative results. Irrespective of which herpesvirus is present, the pathogenesis involves the triggering of inflammatory responses with the immune system causing much of the disease. Themainstay of treatment is therefore topical steroids augmented by antiviral drugs directed against the underlying virus. Treatments are also given to reduce intraocular pressure and to paralyse the ciliary muscle and dilate the pupil with cycloplegics. Oral dosing with acyclovir produces therapeutic intraocular and tear fluid levels sufficient to treat HSV or VZV but, in practice,