Vitrectomy with removal of the internal limiting membrane in chronic diabetic macular oedema

Purpose: To assess the effect of pars-plana vitrectomy including peeling of the internal limiting membrane (ILM) on the resolution of chronic diabetic macular oedema. Methods: We performed a prospective evaluation of 60 eyes of 55 patients with chronic diabetic macular oedema who underwent pars-plana vitrectomy with ILM removal. All patients had a history of macular oedema of at least 6 months. In most of the eyes, grid laser photocoagulation had been performed previously. Eyes with further vitreoretinal pathologies such as vitreous haemorrhage, evident macular traction or significant loss of the foveal capillary net were excluded. Fluorescein angiography, funduscopic examination and the assessment of best-corrected visual acuity (BCVA) were performed pre- and postoperatively. The mean duration of follow-up was 3.0 months. Additionally BCVA was inquired of the referring ophthalmologists after a postoperative period of at least 9 months. Results: Fluorescein angiography and clinical examination revealed a decrease of leakage within the macula or a decrease of macular thickening in 55 (93%) eyes. Mean visual acuity (LogMAR) significantly improved from 1.05 preoperatively to 0.87 postoperatively (P=0.0000034). Twenty-six eyes (43%) gained 2 or more lines of vision; four eyes (7%) lost 2 lines. Data concerning BCVA after a follow-up of at least 9 months were available in 37 patients (41 eyes) and confirmed the results 3 months postoperatively. Conclusion: Pars-plana vitrectomy with ILM peeling reduced macular oedema in most cases. In contrast, visual acuity improved significantly in 43% of the treated eyes only. The discrepancy between anatomical and functional results of ILM removal in chronic diabetic macular oedema is likely to be caused by structural changes of the macula due to long-standing oedema.