Dr Linda Visser, the academic head of the Department of Ophthalmology at the University of KwaZulu-Natal in South Africa, has been treating eye conditions in Human immunodeficiency virus-positive people since 1999.
She said 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, South African website 'Health24' reported.
"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," Visser said.
"Luckily, not in all patients will the centre of the retina be involved. Sometimes it's on the periphery. Then, we can treat it," she added.
Visser explained that about 75 per cent of HIV-infected people will experience some form of eye problem, while about 10 per cent will go totally blind in one or both eyes.
She said blindness in immune-compromised people 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 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 per cent or even more in HIV-positive patients," Visser was quoted as saying by the website.
"But I have seen it in patients who have had transplants and I have seen it in patients with leukaemia and other cancers," she added.
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, she said.
Almost 100 per cent of the population in Africa is born with cytomegalovirus, the viral infection that causes cytomegalovirus retinitis, the report said.
One can live with the viral infection for all his life, but it won't manifest unless the person acquires a condition that severely compromises his immune system.
"It is in the same family as herpes virus. It tends to go into cells and then it sort of becomes dormant there," Visser said.
In Africa, in particular, most people if you draw blood from them and test them for CMV, they will have antibodies to CMV, which means they have had CMV infection sometime in their past, she said.