In non-ischaemic central retinal vein occlusion (niCRVO), the two principal determinants of final visual acuity are visual acuity and the presence of macular oedema at initial presentation.^1,2 Data from the Central Vein Occlusion Study Group² suggested that of patients with CRVO with an initial acuity better than 6/15, 65% maintain this, whereas patients with presenting acuities between 6/15 and 6/60, 81% remain the same or get worse (19% improve to 6/12 or better, 44% remain between 6/15, and 6/60 and 37% are worse than 6/60). Up to 34% of niCRVO may progress to the ischaemic variant with its attendant complications within 3 years.² However, in some studies 83% of indeterminate cases progress to ischaemic CRVO.¹ The creation of a chorioretinal venous anastomosis (CRVA) improved visual acuity in some patients, decreased macular oedema, and reduced the incidence of progression to ischaemic CRVO.^3–5 These important observations provide the basis for the study we carried out.

During the study period 11 patients (table 1) were enrolled according to the trial protocol (see appendix). All anastomoses were patent (on fluorescein angiography and if not repeated, see appendix). Mean patient age and mean pretreatment (T0) visual acuities, retinal thickness (by optical coherence tomography, …