Infectious uveitis: Epidemiology, etiology, diagnostic test performance and treatment

Infectious uveitis is an inflammation of the uveal tract, corresponding to the eye's middle layer, triggered by a response against an infectious agent. This condition is classified into anterior, intermediate, posterior and panuveitis. The most frequent infectious agents in anterior uveitis are viruses, mainly herpes simplex virus. However, it can also be caused by other pathogens such as Bartonella spp., Mycobacterium tuberculosis and Fusarium spp. In intermediate uveitis, syphilis plays a predominant role, while in posterior uveitis various microorganisms are involved, among them Toxoplasma gondii, Cytomegalovirus, Plasmodium spp. and Candida spp. In some instances, as in ocular toxoplasmosis, severe inflammation may involve the entire uvea, resulting in panuveitis. Clinical manifestations of uveitis include ocular pain, redness, myodesopsias, blurred vision, and even vision loss. Direct identification of the causative agent is complex, and the diagnostic performance of available tests varies significantly. For example, polymerase chain reaction (PCR) on ocular specimens for Herpes simplex virus has a sensitivity of 91.3% and specificity of 98.8%, while for toxoplasmosis the sensitivity is 43.1% and specificity 98.5%. Another challenge in infectious uveitis is treatment, as systemic antimicrobials generally have a low penetration into ocular tissue, mostly less than 5%, mainly due to the blood-retinal and blood-aqueous barriers. The efficacy of the molecules in ocular tissue is favored by low protein binding and high liposolubility. This review addresses the most frequent clinical manifestations of bacterial, viral, parasitic and fungal etiologies of infectious uveitis, as well as the diagnostic performance of available tests. In addition, emphasis is placed on the different therapeutic approaches depending on etiology.