RESUMEN
Neovascularization in branch retinal vein occlusion usually develops 6-12 months after the onset of the disease, although some cases have been reported in which neovascularization and subsequent vitreous haemorrhage developed 2-3 years later. This is a report of nine cases of late appearance of vitreous haemorrhage due to branch retinal vein occlusion, which occurred 3-6 years after the initial onset of the disease. In two of these nine cases the vitreous haemorrhage was very profound and had to be managed by vitrectomy. We have studied the remaining seven cases, which had retinal ischaemia and optic disc or retinal neovascularization documented by fluorescein angiographic examination. Laser coagulation was applied in these seven cases, which resulted in considerable regression of the neovascularization and absorption of the vitreous haemorrhage. In one out of the seven cases recurrent vitreous haemorrhages appeared and it was finally treated by vitrectomy. Visual acuity improved in six of the seven cases. The follow-up period ranged from 12 to 48 months. The late appearance of the ischaemic type of branch retinal vein occlusion with neovascularization can be attributed to the change in character of the initially mild oedematous form of the disease. Partial posterior vitreous detachment and traction exerted at some later stage upon the neovascularization could be additional factors of the late appearance of vitreous haemorrhage. Patients with branch retinal vein occlusion should be followed up regularly over a long period of time in order to avoid late complications of the disease, such as vitreous haemorrhage following optic disc or retinal neovascularization.