Conjunctivitis and keratitis are common forms of ocular morbidity seen in general practice and eye units.1 2 The aetiology of these diseases includes viral, bacterial, or parasitic infection as well as allergy, trauma, and dietary deficiency. Among the common microbial causes3-7 (Table 1) are adenovirus, herpes simplex virus (HSV), and Chlamydia trachomatis. Ocular adenovirus infections occur throughout the world in both sporadic and epidemic forms, and large scale outbreaks of epidemic keratoconjunctivitis can occur in hospitals, schools, military establishments, or factories.8 HSV type 1 ocular infection occurs in all countries with an annual incidence of up to 20.7 per 100 000 population and is the most common infective cause of blindness in developed countries.4 9 Trachoma caused byC trachomatis serovars A–C is the leading infectious cause of blindness in the world and is a major public health problem in developing countries.10 Adult chlamydial conjunctivitis, caused by C trachomatisserovars D–K, is an oculogenital infection and up to 90% of patients have concurrent genital infection.11-13 Chlamydial neonatal conjunctivitis (ophthalmia neonatorum) develops in 18%–74% of babies born to mothers with genital chlamydial infection.7

This article reviews available diagnostic laboratory techniques for keratoconjunctivitis caused by adenovirus, HSV, andC trachomatis with special emphasis on modern molecular diagnostic techniques. For information on the clinical features, epidemiology, and treatment of these infections the reader is referred to a number of other reviews.8 9 14-17