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Response to Vitrectomy in diabetic macular edema

      Dear Editor:
      We thank Dr. Tripathy for his interest in our manuscript and we welcome this opportunity to address his questions.
      Diabetic macular edema (DME) develops in approximately 30% of patients who have had diabetes for more than 20 years and constitutes a major cause of visual impairment worldwide.
      • Klein R.
      • Klein B.E.
      • Moss S.E.
      • Davis M.D.
      • DeMets D.L.
      The Wisconsin epidemiologic study of diabetic retinopathy. IV. Diabetic macular edema.
      Identifying treatments that can effectively treat DME is critical to managing the increasing number of affected patients.
      The main difference between ours and previously published vitrectomy studies is that we included only treatment-naïve eyes. Patients enrolled in our study were neither randomized to treatment nor were they consecutively seen in our clinic. Treating surgeons tended to treat patients with better prognoses (better baseline visual acuity and less ischemia) with anti-vascular endothelial growth factor (VEGF) injections, whereas patients with worse prognoses were offered vitrectomy. This helps explain why our patients’ initial visual acuities were worse than those usually seen in clinical trials. However, we believe that the impressive average visual acuity improvements among our patients suggest a role for vitrectomy in the initial treatment of DME in eyes with poor initial vision. In our study, vitrectomy for DME was both safe and durable with more than 80% of patients experiencing improvement in visual acuity.
      • Michalewska Z.
      • Stewart M.W.
      • Landers 3rd, M.B.
      • Bednarski M.
      • Adelman R.A.
      • Nawrocki J.
      Vitrectomy in the management of diabetic macular edema in treatment-naïve patients.
      Since ours was a retrospective study, follow-up visits after six months were not scheduled consistently and longer term follow-ups were not always available. For this reason, we chose six months as the primary temporal endpoint. This strategy allows our data to be directly compared to the anti-VEGF trials, in which the six-month visual acuity results are universally available and do not differ significantly from those at 12 months. A recent study presented the long-term (mean follow-up of 37 months) results of vitrectomy for center-involving DME in previously treated and treatment-naïve eyes. The mean visual acuity improved from 20/100 to 20/63 at month twelve (N=53)
      • Browning D.J.
      • Lee C.
      • Stewart M.W.
      • Landers 3rd, M.B.
      Vitrectomy for center-involved diabetic macular edema.
      .
      The visual acuity numbers in Table 1 are correct but unfortunately the wrong number was included in the discussion. In Europe, visual acuities are usually measured on the decimal scale and an error may have occurred when these were converted to Snellen fractions.
      We agree that optic nerve function and diagnostic tests for glaucoma may be of interest in diabetic patients but we did not include optical coherence tomography measurements of the nerve fiber layer in the study protocol. Seki and coworkers found that patients with proliferative diabetic retinopathy and coexisting renal dysfunction are at high risk of developing optic atrophy after vitrectomy
      • Seki M.
      • Togashi H.
      • Ando N.
      Optic nerve atrophy after vitrectomy for diabetic retinopathy: its systemic and local risk factors.
      and vitrectomy for macular holes or epiretinal membranes may be associated with a decrease in retinal nerve fiber layer thickness.
      • Lalezary M.
      • Shah R.J.
      • Reddy R.K.
      • Kammer J.A.
      • Kuchtey R.W.
      • Joos K.M.
      • Cherney E.F.
      • Recchia F.M.
      • Kim S.J.
      Prospective Retinal and Optic Nerve Vitrectomy Evaluation (PROVE) study: twelve-month findings.
      We agree that nerve fiber layer damage may occur during surgery and encourage future researchers to investigate this.
      Based on the data from ours and many other studies, we believe that a multicenter, randomized, clinical trial comparing the efficacy, safety, and cost of vitrectomy versus intravitreal anti-VEGF therapy is warranted.

      References

        • Klein R.
        • Klein B.E.
        • Moss S.E.
        • Davis M.D.
        • DeMets D.L.
        The Wisconsin epidemiologic study of diabetic retinopathy. IV. Diabetic macular edema.
        Ophthalmology. 1984; 91: 1464-1474
        • Michalewska Z.
        • Stewart M.W.
        • Landers 3rd, M.B.
        • Bednarski M.
        • Adelman R.A.
        • Nawrocki J.
        Vitrectomy in the management of diabetic macular edema in treatment-naïve patients.
        Can J Ophthalmol. 2018. Aug; 53: 402-407
        • Browning D.J.
        • Lee C.
        • Stewart M.W.
        • Landers 3rd, M.B.
        Vitrectomy for center-involved diabetic macular edema.
        Clin Ophthalmol. 2016; 26: 735-742
        • Seki M.
        • Togashi H.
        • Ando N.
        Optic nerve atrophy after vitrectomy for diabetic retinopathy: its systemic and local risk factors.
        Nippon Ganka Gakkai Zasshi. 2006; 110: 462-467
        • Lalezary M.
        • Shah R.J.
        • Reddy R.K.
        • Kammer J.A.
        • Kuchtey R.W.
        • Joos K.M.
        • Cherney E.F.
        • Recchia F.M.
        • Kim S.J.
        Prospective Retinal and Optic Nerve Vitrectomy Evaluation (PROVE) study: twelve-month findings.
        Ophthalmology. 2014; 121: 1983-1989