Contributor: Gordon K. Klintworth
Several different virus families are known to infect the eye and its adnexa. Pathogenic DNA viruses include members of the Poxvirus [poxvirus infection] [variola, vaccinia, molluscum contagiosum], Herpesviruses [herpes virus infection] [Herpes simplex virus type 1 [Herpes simplex], Herpes simplex virus type 2, cytomegalovirus [cytomegalovirus infection], varicella-zoster virus [varicella-zoster virus infection], Epstein-Barr virus [Epstein-Barr virus infection] and simian Herpes B), Adenovirus (types 1-11, 14-17, 19, 20, 22, 26, 27,37) [adenovirus infection] and the Papovavirus [Papovavirus infection] families. Herpes simplex virus type 1 is the commonest viral cause of clinically significant corneal disease. Rarely Herpes simplex virus type 2 and Herpes virus simiae cause ocular infection. Cytomegalovirus commonly involves the retina, particularly in immunosuppressed individuals such as renal graft recipients [renal disease] and persons with AIDS.
RNA viruses affecting the ocular tissues include members of the Myxovirus [myxovirus infection][influenza], Paramyxovirus [paramyxovirus infection],[rubeola, mumps, Newcastle disease], togavirus [togavirus infection] [rubella, yellow fever, sandfly fever], picornavirus [picornavirus infection] (bovine foot and mouth, coxsackievirus [coxsackievirus infection]) and rhabdovirus [rhabdovirus infection] (Marburg virus)).
and the HIV-1 and HIV-2 (AIDS). Also rabies can be transmitted by a corneal graft. Mumps can cause conjunctivitis, episcleritis, iritis and keratitis.
Papillomavirus probably causes warts and papillomas of the eyelids and conjunctiva as well as squamous dysplasias and carcinomas of the conjunctiva and eyelid. Papillomavirus common antigen has been identified by immunohistochemical methods in conjunctival papillomas and in situ hybridization. Human papillomavirus type 16 (HPV 16) has been demonstrated in a recurrent squamous cell carcinoma of the lower eyelid using the polymerase chain reaction.
A strong causal relationship exists with the Epstein Barr virus and Burkitt lymphoma, which often involves the orbit, and is the most common cause of proptosis among children in parts of Africa.
Rubella virus infection during the first trimester of pregnancy can cause cataracts, deafness and mental retardation. Later in pregnancy, the effects are less frequent and less severe.
Cytomegalovirus is the most common opportunistic infection of the retina and systemic immune suppression predisposes to it. One percent of infants are infected in utero; a further 8-60% become infected during the first six months of life mostly from breast milk.
Recurrent bouts of Herpes simplex keratitis are thought to be triggered by environmental factors that include sunlight and physical trauma.
The retroviruses are a large group of enveloped RNA viruses. They contain the enzyme reverse transcriptase, which synthesizes DNA copies of the viral RNA in the host and this DNA becomes incorporated into the DNA of the host. New viral DNA is transcribed from the integrated viral DNA.The retroviruses were first described by Rous and his colleagues as the cause of a sarcoma in chickens. At least four classes of human retroviruses are recognized: the oncoviruses (which include human T lymphotropic virus (HLTV-1), the lentiviruses (which include the human immune deficiency viruses (HIV-I) and HIV-II that cause AIDS) and the leukoviruses. The human T lymphotropic virus (HLTV-1) has an affinity for T-cells.