The single most common diagnosis assigned to patients with uveitis is “idiopathic,” and in a recent large epidemiological study 48% of new cases of uveitis were assigned this diagnosis.¹ However, with the development of new diagnostic technologies, the discovery of novel ocular pathogens, and the recognition that established ocular pathogens can present in previously unrecognised ways, fewer patients are now being diagnosed with “idiopathic” uveitis. Examples of novel ocular pathogens include Bartonella henselae,²Borrelia burgdorfi,³ West Nile virus,⁴Tropheryma whippelii,⁵ microsporidia,⁶Baylisascaris procyonis,⁷ and the leptospires.⁸ Examples of established ocular pathogens that can present in previously unrecognised ways include atypical presentations of toxoplasmosis,^9,10 herpesviruses as the cause of the acute retinal necrosis syndrome^11,12 and some cases of Posner-Schlossman syndrome,¹³ and varicella zoster virus as the cause of progressive outer retinal necrosis.¹⁴ In addition, two independent groups recently reported evidence linking rubella virus with Fuchs’ heterochromic iridocyclitis.^15,16 In the current issue of the BJO (p 852), de Shryver et al present evidence in support of cytomegalovirus (CMV) as a cause of hypertensive iritis in immune competent individuals.¹⁷

CMV is an extremely common human pathogen, infecting …