Disruption of the choroidoretinal interface by toxoplasma.

Toxoplasmosis is a common zoonotic infection of the retina caused by Toxoplasma gondii. The disease causes severe damage that affects the retina and subjacent choroid. Invasion of the retinal cells by the parasite leads to the major damage seen in the retina. Subsequent reactions to the invasion by toxoplasma leads to the influx of inflammatory cells. Although hypersensitivity reactions have been described to both toxoplasma and to retinal autoantigens, the major disruption of the choroidoretinal interface is probably secondary to the tissue invasion by the parasite. Patients with AIDS may show extensive necrosis of the retina in the absence of inflammatory cells. Healing of the active lesion leads to scar formation. Toxoplasma retinochoroiditis may be pigmented, nonpigmented or punched-out. Vascular anastomoses between the retina and choroid, retinal and subretinal neovascularization may occur in the aftermath of choroidoretinal interface disruption.