Doctors say HIV infection when left undiagnosed and untreated for a long time, can trigger off a dormant virus called cytomegalovirus (CMV), which can lead to blindness.

Cytomegalovirus is the most common cause of blindness in people who have HIV.

Dr Linda Visser, the academic head of the Department of Ophthalmology at the University of KwaZulu-Natal, has been treating eye conditions in HIV-positive people since 1999.

She says Aids-related cytomegalovirus retinitis affects the retina, the neural tissue of the eye. If the tissue is damaged, it cannot be re-generated. However, if the part of the retina that is responsible for vision is not affected, the condition can be treated.

"They get necrosis of the retina, which is the white area. And the macular is the centre of the retina and once your macular has become necrotic, you cannot see. There's nothing one can do to bring it back. Luckily, not in all patients will the centre of the retina be involved. Sometimes it's on the periphery. Then, we can treat it," News24 quoted her as saying.

According to Dr Visser, about 75 percent of HIV-infected people will experience some form of eye problem, while about 10 percent will go totally blind in one or both eyes.

She said blindness in immune-compromised people, such as HIV-patients, is most commonly caused by a viral infection called cytomegalovirus, which normally thrives on a weakened immune system.

"It is actually only seen in patients who are in immune-compromised. We never see it in immune-competent patients. And because in our set-up, HIV is the most common cause for immune suppression, we see it probably 95 percent or even more in HIV-positive patients. But I have seen it in patients who have had transplants and I have seen it in patients with leukaemia and other cancers," she said.
She stated that in HIV-infected people, the infection manifests when they've left their condition for too long without having it treated and their CD 4 counts have fallen to dangerous levels.