Central retinal artery occlusion (CRAO) is an ophthalmic emergency, associated with catastrophic visual loss. Since von Graefe described it in 1859,1 many treatments have been proposed to improve visual outcome, including ocular massage, reduction in intraocular pressure, antiplatelet therapy, heparin therapy, vasodilators, isovolumic haemodilution, hyperbaric oxygen, and embolectomy. None, however, has stood the test of time. Intra-arterial thrombolysis is currently the most widely advocated therapy,2^–12 and success has been enthusiastically claimed for it. The role of intra-arterial thrombolysis in CRAO has recently been discussed in reviews,13 14 one of which is published in this issue of this Journal (see page 588).15

The objective of the present discussion is to consider the question of intra-arterial thrombolysis in CRAO in the light of available scientific facts. A brief discussion is first required of those various basic crucial issues, which determine the effectiveness or ineffectiveness of any therapy. These include the following:

1. Scientific basis: The first essential, does a therapy have a scientific rationale? Without it, any treatment must eventually prove useless or even harmful. One classic recent example of this was optic nerve sheath decompression for non-arteritic anterior ischaemic optic neuropathy.16 That study was first published on an expedited basis and became popular worldwide but was proved by a multicentre randomised clinical trial17 to be harmful: 24% of those with decompression suffered further visual loss, compared with only 12% who were left alone, because the whole procedure had no scientific rationale.18

2. Natural history of disease: The gold standard is to compare the outcome of a treatment with the natural history of the disease. It is not unusual to find natural history being attributed as the beneficial effect of a treatment. For example, Richard et al4 claimed visual acuity improvement in …