Contributor. Gordon K. Klintworth
Retinitis is accompanied by the usual manifestations of inflammation that occur in other tissues. These include vasodilatation, the margination of leukocytes within the microvasculature and the emigration of these cells into the tissue. Edema of the affected region [edema - retina] follows an accumulation of protein-rich extracellular fluid. The causes of retinitis include infectious agents that may reach the retina by the blood stream as part of a systemic infection, as in puerperal sepsis and meningococcemia. Other infectious causes of retinitis include fungi (Aspergillus [aspergillosis], Pseudallescheria [pseudoallescheriasis], Candida [candidiasis], Cryptococcus neoformans [cryptococcosis]), bacteria (Mycobacterium tuberculosis [tuberculosis], Mycobacterium leprae [leprosy], Borrelia burgdorferi [Lyme disease], Tropheryma whippelii [Whipple disease], Rochalimaea hensalae [cat scratch disease]), Rickettsia [Rickettsial infection], viruses (measles, rubella, herpesvirus type 1, cytomegalovirus [cytomegalovirus retinitis], varicella-zoster virus [Herpes zoster], Rift valley fever, and Coxsackie virus B4). Retinal infection by bacteria such as Hemophilus [Hemophilus infection], Streptococcus [streptococcal infection], Neisseria meningitidis [Neisserial infection] result in an acute septic retinitis that usually evolves rapidly into a endophthalmitis. Some viruses, such as herpesvirus type 1 and varicella-zoster virus can lead to acute retinal necrosis. Retinitis may remain localized to the retinal tissue or it may spread to involve the vitreous [vitritis], optic nerve [optic neuritis], and uvea [uveitis]. Particularly when due to an infection retinitis can evolve into endophthalmitis or panophthalmitis.