A 27-year-old man from the Caribbean, who is known to have sickle cell disease, presents with floaters and reduced vision. What is going on?

Sickle cell disease is a blood disorder in which the red blood cells are sickle-shaped (see image) and not a biconcave disc and they should be. Red blood cells carry oxygen around the body. Sickle-shaped blood cells (are destroyed by the body faster than normal blood cells, which can result in an inadequate oxygen supply to the body (anaemia). Most people with sickle cell disease have at least mild symptoms of chronic anaemia, including weakness and fatigue, pale appearance, yellowing of the skin and the whites of the eyes (jaundice) and shortness of breath. African-Caribbean people have a risk for sickle cell disease.

Sickle-shaped blood cells become stuck (because of their shape and rigidity) and block small blood vessels throughout the body. Reduced blood flow caused by blocked blood vessels can damage certain organs, muscles, and bones. This may cause repeated episodes of pain (called sickle cell crises) that may last from hours to days. The pain most often occurs in the bones of the spine, arms and legs, the chest, and the abdomen.

In the eye, small blood vessels can become blocked leading to haemorrhage. If a substantial amount of blood leaks, the vitreous can be partially or totally filled with blood resulting in a catastrophic loss of vision. An examination by an ophthalmologist is required.