This is a benign tumour consisting of abnormal blood vessels.
Fluid leaking from the tumour collects beneath the retina, causing distorted vision and blurred vision. If the amount of fluid beneath the retina is excessive and if the retina becomes totally detached, then abnormal blood vessels can develop on the iris (i.e., 'rubeosis' or 'iris neovascularisation'). These can block the outflow of fluid from the eye to cause an increase in pressure (i.e., 'neovascular glaucoma'), which can be painful.
The circumscribed variety usually becomes noticeable in middle age. A diffuse variety occurs in younger patients as part of the Sturge Weber Syndrome, which is characterized by a red birthmark on the skin of the face.
The photograph, taken with a standard fundus camera, shows a circumscribed choroidal haemangioma in the right eye. The tumour is just reaching the fovea, which is the diffuse, darker area at the centre of the photograph.
Circumscribed choroidal haemangioma of the left eye photographed with a Panoret Camera
Until recently, patients with choroidal haemangioma required radiotherapy but now we are able to achieve equally good results with photodynamic therapy, which is much more convenient and equally effective, with less risk of side-effects.