Diabetic macular oedema: pilot randomised trial of pars plana vitrectomy vs macular argon photocoagulation

Focal macular photocoagulation for clinically significant macular oedema (CSME) is the proven method for treatment of this condition, but with little chance of visual improvement. Pars plana vitrectomy (PPV) may produce resolution of macular oedema and improvement in visual acuity. However, there have been no randomised trials to ascertain role of vitrectomy in the management of persistent CSME.

Patients with persistent CSME despite previous macular photocoagulation and Snellen visual acuity 6/15 to 6/60 were recruited. Dilated fundoscopy, best-corrected visual acuity including Early Treatment Diabetic Retinopathy Study (ETDRS) vision, ocular coherence tomography and fundus fluorescein angiography (FFA) at baseline and up to 12 months post-treatment was performed. Exclusion criteria were signs of posterior vitreous detachment, macular traction or the taut posterior hyaloid face syndrome, or macular ischaemia on FFA. In all, 20 patients were randomised (10 in each arm) to either standard macular photocoagulation or PPV and removal of the posterior hyaloid face.

Of the 20 patients recruited, seven patients completed the protocol in the vitrectomy and eight in the laser arms, respectively. There was little evidence of any difference in the foveal thickness at 12 months between the two treatment arms despite a gradual improvement. Only one patient, from the vitrectomy arm, suffered moderate visual loss (defined as loss of 15 ETDRS letters) (our primary outcome).

In this pilot RCT, standard PPV provides little visual benefit compared to macular photocoagulation, but a larger definitive study is required to confirm this early appraisal.