Vision loss in HIV is commonly due to infection with: March 2005 March 2013 (h)
**Core Concept**
Toxoplasmosis is a protozoal infection caused by *Toxoplasma gondii* that can lead to vision loss in immunocompromised patients, particularly those with HIV/AIDS. This is due to the reactivation of latent infection in the central nervous system, including the retina.
**Why the Correct Answer is Right**
Toxoplasmosis infection in HIV/AIDS patients often results from the reactivation of latent *Toxoplasma gondii* cysts in the retina and brain. The parasite invades the retinal layers, leading to necrotizing retinitis, which can cause severe vision loss. The immune system's inability to control the infection in HIV/AIDS patients allows the parasite to proliferate and cause significant damage.
**Why Each Wrong Option is Incorrect**
* **Option A:** CMV retinitis is a common cause of vision loss in HIV/AIDS patients, but it is not the most common cause. CMV retinitis typically presents with a characteristic "pizza pie" pattern of retinal necrosis.
* **Option B:** Herpes simplex virus (HSV) can cause retinitis in immunocompromised patients, but it is less common than toxoplasmosis and CMV retinitis. HSV retinitis often presents with a more localized area of retinal necrosis.
* **Option D:** Tuberculosis (TB) can cause various ocular manifestations, including uveitis and retinitis, but it is not a common cause of vision loss in HIV/AIDS patients.
**Clinical Pearl / High-Yield Fact**
In HIV/AIDS patients, the combination of antiretroviral therapy and antiparasitic treatment can significantly reduce the risk of toxoplasmosis-related vision loss.
**Correct Answer: C. Toxoplasmosis**