A Call for a Comparative Trial Of Early Vitrectomy
MAURICE B. LANDERS, III, MD • VERONICA A. KON GRAVERSEN, MD • MICHAEL W. STEWART, MD
Diabetic macular edema has been treated with vitrectomy for two decades, although its use has been reserved primarily for eyes that have responded poorly to conventional therapy. Our review of data from 37 studies has shown that vitrectomy effectively decreases macular edema (by an average of -187 µm).
However, many of these studies, particularly in the recent DRCR.net study of vitrectomy in patients with DME, found no significant improvement in visual acuity was found, even after the resolution of macular edema. The vast majority of these patients underwent vitrectomy only after other treatments, such as focal and grid laser and intravitreal injections of steroids and/or anti-VEGF drugs, had been tried and had failed to resolve the DME.
Significantly, all of these studies, including the DRCR.net study, were done prior to the advent of SD-OCT and the potential for evaluation of the integrity of the outer retina that it provides.
Chhablani et al.1 showed that the preoperative integrity of the outer retina, as measured with SD-OCT, correlates well with the visual acuity obtained after vitrectomy in patients with DME. In a prospective pilot trial, Murata2 showed the value of ELM and IS/OS integrity in predicting the likelihood of postoperative visual improvement.
WHAT THIS MEANS
Our current approach to the management of diabetic macular edema needs improvement. Injecting anti-VEGF drugs into the vitreous of diabetic patients is prohibitively expensive, both due to the cost of the best drugs currently available, and the burden that frequently repeated visits to the eye clinic placed on patients and their families.
The sight-threatening aspects of multiple injections bear consideration. After 30 intravitreal injections, the summed risk of endophthalmitis approaches 1%, which is approximately the risk of sight-threatening outcomes following vitrectomy.
The beneficial effect of vitrectomy on DME appears to be long lasting. In 37 series in the English literature, including the DRCR.net studies, the reduction in macular edema following vitrectomy lasted, in the vast majority of patients, for the duration of the study, commonly one or two years and, in some studies, for five and even seven years.
Vitrectomy should be (re)evaluated as a primary treatment for diffuse DME, using all appropriate contemporary technology to predict the potential for a particular patient to obtain significantly improved vision. A well-done, controlled, randomized clinical trial should compare early vitrectomy to anti-VEGF drug injections and laser photocoagulation of the macula as a treatment for diffuse DME. RP
1. Chhablani JK, Kim JS, Cheng L, et al. External limiting membrane as a predictor of visual improvement in diabetic macular edema after pars plana vitrectomy. Graefes Arch Clin Exp Ophthalmol. 2012;250:1415-1420
2. Murata, T. Paper presented at the Vail Vitrectomy Symposium; Vail, CO; March 18, 2013.