If the body is immunocompromised for some reason, such as anti-rejection drugs for transplant recipients or HIV/AIDS, then the body and the eye are susceptible to a whole host of infectious microorganisms that would otherwise be less harmful. These include cytomegalovirus (CMV), herpes zoster virus (chicken pox/shingles virus), herpes simplex virus (cold sore virus), mycobacterium (including tuberculosis), toxoplasmosis, pneumocystis, syphilis, cryptococcus, histoplasmosis, and other fungal infections. Lymphoma is also more common in these patients.

Rapid diagnosis and treatment with the correct antimicrobials are essential to minimize damage done to the eye from these infections. These antimicrobials can be systemic (oral or intravenous) or intraocular injections/implants in the vitreous cavity. Many cases are without symptoms at first, thus requiring regular dilated examination while the patient remains immunocompromised. Even with prompt and correct treatment, the damage these infections can cause include vitreous hemorrhage, retinal detachment, retinal scar tissue formation, cataract, among others. These complications may require vitrectomy and/or scleral buckle surgery to repair.