When the retina becomes infected, it is called "retinitis". A variety of organisms (viruses, bacteria, fungi, and parasites) may cause retinitis, but the most common is a virus called cytomegalovirus or CMV. CMV retinitis is most commonly seen in patients with AIDS or other causes of immunosuppression. In most cases, CMV retinitis can be treated with intravenous medications (such as Gancyclovir or Fascarnet).

In some cases, the retinitis causes the retina to become very sick, weak, and thin. Retinal holes may develop in the thinned parts of the retina. A retinal detachment can occur and when it does, vitrectomy surgery combined with laser treatment and the placement of silicone oil in the eye, can reattach the retina and prevent further loss of vision. In almost all cases, the silicone oil stays in the eye permanently.