Effect of Intraoperative Dexamethasone Implant in Taut Posterior Hyaloid Removal in Diabetic Macular Edema

• change in central macular thickness [ Time Frame: Baseline to 3 months ] [ Designated as safety issue: No ]
  The primary outcome measure is the change in the central macular thickness, either an increase or decrease, as measured by optical coherence tomography as compared to the preoperative thickness
  
  

• change in visual acuity [ Time Frame: Baseline to 3 months ] [ Designated as safety issue: No ]
  Change in the visual acuity as measured by the logMAR visual acuity chart
  
  

This study is undertaken to determine effect of sustained release dexamethasone implant,Ozurdex in improving outcome of taut posterior hyaloid removal in patients with diabetic macular edema

Diabetic macular edema constitute important cause of visual impairment in patients with diabetes.Focal/ grid laser photocoagulation is the standard of care in the management .Several adjuncts including intravitreal corticosteroids, Pegaptanib Sodium , Ranibizumab , Bevacizumab are also been tried.In some patients inspite of multiple lasers or injections macular edema persists as a consequence overlying taut posterior hyaloid membrane which needs to be removed by vitrectomy. The exact role of vitreous in the pathogenesis of diabetic maculopathy remains unclear although it has been implicated as a cause of macular edema via several mechanical and physiologic mechanisms, which include the following (1) destabilization of the vitreous by abnormal glycation and crosslinking of vitreal collagen, leading to traction on the macula, (2) accumulation and concentration of factors causing vasopermeability in the premacular vitreous gel and (3) accumulation of chemoattractant factors in the vitreous, leading to cellular migration to the posterior hyaloid, contraction and macular traction. The observation that release of mechanical traction on the macula with subsequent reduction in DME, either by spontaneous posterior vitreous detachment or with vitrectomy, lends support to this line of reasoning. Furthermore, the evidence that vitrectomy produces improved retinal oxygenation taken together with the evidence that increased oxygenation can reduce DME, suggests an additional physiologic advantage but determination of which eyes might benefit from vitrectomy is the most challenging aspect in the treatment of this condition. Fluorescein angiography, B-scan ultrasonography, and optical coherence tomography may be helpful in this regard. Most often, vitreous surgery is performed when diabetic macular edema persists despite multiple laser treatments. All reports published to date regarding vitrectomy for diabetic macular edema are uncontrolled and nonrandomized patient series. Visual improvement after vitrectomy is related to the duration of edema, as well as the extent of intraretinal lipid and vascular nonperfusion.Even after surgery some patients might need repeat intravitreal bevacizumab or triamcinolone injections to take care of residual macular edema.Intravitreal Triamcinolone Acetonide (TA), a water insoluble steroid, has been shown to reduce the retinal thickness and improve the visual acuity. However, recurrence of macular edema in patients who receive intravitreal TA is a major concern because of its short half life . In search for the ideal corticosteroid preparation, a Dexamethasone Posterior Segment Drug Delivery System (Dexamethasone DDS - Ozurdex®, Allergan Inc, Irvine, California) was recently developed which has generated new interest in this molecule. It is a sustained release intravitreal implant containing 700µg dexamethasone has been approved by the US-FDA (Food and Drug Administration) for treatment of macular edema in retinal vein occlusions. The present study introduces a novel concept of using intraoperative Ozurdex ® implant during taut posterior hyaloid removal and its effect in improving the surgical outcome