Clinical and autopsy studies show that up to 75% of patients with AIDSwill have ocular findings. All part of visual system can be affected byAIDS. Ocular involvement can also be the presenting sign of AIDS. Becauseof the high frequency of ocular involvement, it is appropriate to ophthalmologiststo be knowledgeable concerning this condition.
The most common ocular manifestation of AIDS is a form of retinopathyconsisting of cotton-wool spots, hemorrhages, and capillary abnormalities.This retinopathy is seen in up to 71% of patients with AIDS and is usuallyasymptomatic. The etiology of the cotton-wool spots is the subject of controversy,it was initially thought that these microvascular changes were the resultof hematological abnormalities. An alternative theory proposed that cotton-woolspots were an early manifestations of cytomegalovirus (CMV) retinitis.Culture and histopathological studies of this lesions, however, has beennegative for opportunistic pathogens, such as CMV, although the lesionsare frequently associated with systemic CMV infection. It has been suggestedthat AIDS retinopathy is the result of endothelial damage by circulatingimmune complex.
The exact role of HIV in AIDS retinopathy has also been investigated. Testing for HIV using in situ hybridization techniques has failed toidentify HIV genomes in the retina . HIV has been recovered from the retinaby culture from patients with AIDS, and, in one case, HIV was localizedwithin the retinal vascular endothelium by immunofluorescent techniques.Therefore,it is possible that the microvascular changes of AIDS retinopathy are thedirect result of HIV infection.
CMV retinitis is the most common ocular opportunistic infection in patientswith AIDS. It presents as a necrotizing retinitis with associated retinalhemorrhages and vasculitis. A typical lesion is a zone of white retinalinfiltration with translucent, slightly irregular margins. Multicentricorigin and bilateral disease are frequently seen. As the lesions mature,they become more granular and ultimately become transparent. Faint pigmentstippling is seen at the level of the retinal pigment epithelium. Focaldeposits of lipid , calcium, and glial tissue may be seen within inactivelesions. The retinal vessels become markedly attenuated, and secondaryoptic atrophy develops. A zone of active necrotizing retinitis remainsat the margin of the inactive lesion.
The reason for the high incidence of CMV retinitis in the AIDS populationis unclear. Clinical and autopsy series indicate a prevalence of 17% to34%. Other immunocompromised patients, such as the organ transplant population,have much lower prevalence of CMV retinitis, although the rate of CMV viremiais quite high.
One possible explanation of the high prevalence of CMV retinitis inthe AIDS population is interaction with other viruses, particularly HIV.In the retina, HIV appears to infect the retinal vascular endothelium andis likely the cause of AIDS retinopathy. CMV is a neutropic virus and isless likely to infect retinal vascular endothelium. In the presence ofboth viruses, HIV may cause endothelium damage, allowing CMV access toretinal tissue.
There are several mechanisms for visual loss in CMV retinitis. Absolutescotomata correspond to zones of inactive retinitis. ischemia and edemaadjacent to active zones may lead to visual loss, particularly in the macula.CMV may affect the optic nerve, causing a loss of vision either by directinfection or by secondary ischemic damage. CMV retinitis may result inretinal detachment in up to 29% of cases. Retinal holes typically occurnear the posterior border of inactive zones of necrotizing retinitis. Asignificant number of patients develop proliferative vitreoretinopathy.Repair of these detachments frequently requires vitrectomy techniques,and the results of surgery are poor.
Without treatment, CMV retinitis is relentlessly progressive, leadingto loss of vision from involvement of the optic nerve and macula or fromretinal detachment. It typically progresses over a period of months, withexpansion of old lesions and development of new ones.
Before 1983, treatment of CMV retinitis was usually ineffective. In1984, ganciclocir, a derivative of acyclovir, become available. There isoverwhelming clinical evidence that ganciclovir is effective in the managementof CMV retinitis and other systemic CMV infections. Unfortunately, thedrug is virostatic and must be taken indefinitely, unlike acyclovir. Furthermore,ganciclovir has significant systemic toxicity. Maintenance treatment withganciclovir is complicated by significant myelosuppression requiring discontinuationof the drug in 30% to 50% of patients. Intravitreal treatment with ganciclovirhas been reported and appears to be an effective alternative in those patientswho cannot be treated systemically.
Foscarnet is another antiviral agent that is effective against CMV,with a slightly different spectrum of toxicity. Nephrotoxicity is the mostsignificant adverse effect of foscarnet. Because of the different toxiceffects to the two drugs, they may be used sequentially to control CMVretinitis.
Opportunistic infections other than CMV are much less common. Otherviruses of the herpes group, including both herpes simplex and herpes zoster,may cause necrotizing retinitis. Protozoan infections with either Pneumocystiscarinii or Toxoplama gondii are also seen in the AIDS population.Toxoplasmosismay present with a particularly fulminant retinochoroiditis resemblingendophtalmitis. Pneumocystis has been associated with cotton-wool spots,but until recently, it was uncertain whether Pneumocystis was a cause ofretinal infection. It is known that disseminated Pneumocystis may causea multifocal choroiditis that may remain asymptomatic for long periodsof time. The characteristic changes in fundus are large, yellow, placoidlesions located in the choroid, without overlying retinal or vitreous involvement.The choroiditis will respond to specific systemic treatment. Mycobacterialinfection as a complication of systemic M. avium intracellulare has alsobeen reported. Fungal infections with Candida, Histoplasma, and Cryptococcushas also been reported. Cryptococcus is a common opportunistic pathogenin the central nervous system. Ocular involvement usually occurs secondaryto meningeal infection extending along the optic nerve sheath. Syphilisis usually a rare cause of ocular disease, but, in the AIDS population,syphilis is not infrequently seen, and retinochoroiditis has been reported.
Kaposi’s sarcoma is the most common neoplastic disease in patients withAIDS. Kaposi;s sarcoma classically involves the lower extremities and visceralorgans, but, in patients with AIDS, the disease is much more aggressive,causing lesions on the face and ocular surface, lid dysfunction, and orbitalpain. The lesions usually require no treatment, but they can be locallyexcised or treated with radiation or chemotherapy. Non-Hodgkin’s lyphomais the second most common neoplasm.
In Africa, Burkitt’s lyphoma is frequently associated with AIDS andmay involve the orbit in up to 50% of cases. The association of Burkitt;slyphoma with the Epstein-Barr virus (EBV) raises the possibility of viralinteraction of EBV and HIV, which may explain the disseminated nature ofthe disease in the AIDS population.
Probably the most common neurological manifestation of AIDS is dementia,but the visual system is also affected as a result of CNS involvement.Eye movement disorders, disconnection syndromes, visual field defects,and pupillary abnormalities have also been reported. Neuro-ophthalmologicsigns and symptoms are also associated with various opportunistic infectionsof the central nervous system.
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