Intraoperative Dexamethasone Implant Improves Outcome of Cataract Surgery With Diabetic Macular Edema

• change in the central macular thickness [ Time Frame: Baseline and 6 MONTHS ] [ Designated as safety issue: No ]
  The primary outcome 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 the visual acuity [ Time Frame: Baseline and 6 MONTHS ] [ Designated as safety issue: No ]
  Change in the visual acuity as measured by the ETDRS visual acuity scale
  
  

Diabetic Macular Edema (DME) and cataract constitute important causes of visual impairment in patients with diabetes mellitus. Cataract surgery in patients with diabetic retinopathy is associated with progression of both retinopathy and maculopathy in nearly 23-57% of cases, thus affecting the final visual outcome. Post-cataract surgery, macular edema may be due to worsening/presence of pre-existing clinically significant macular edema (CSME) or due to development of Irvine Gass Syndrome where cystoid macular edema (CME) occurs in the post operative period and is believed to be inflammatory in origin. Focal/ grid laser photocoagulation is the standard of care in the management of CSME, which may be pre-existing at the time of cataract surgery or worsens following surgery. Several adjuncts including intravitreal corticosteroids, Pegaptanib Sodium (Macugen; Pfizer, New York), Ranibizumab (Lucentis; Genentech, South San Francisco, California), Bevacizumab (Avastin, Genentech) have been tried in an attempt to improve the visual results.

Several modalities such as non-steroidal anti-inflammatory agents, carbonic anhydrase inhibitors, corticosteroids, hyperbaric oxygen, laser photocoagulation and vitrectomy with internal limiting membrane peeling have been tried for managing inflammatory cystoid macular edema13. Intravitreal Triamcinolone Acetonide (TA), a water insoluble steroid, has been shown to reduce the retinal thickness and improve the visual acuity14-16. However, recurrence of macular edema in patients who receive intravitreal TA is a major concern as the patients need multiple repeat injections because of the short half life of the drug (18.6 days). A more potent steroid, dexamethasone has also been tried as an alternative to TA for macular edema; however, its short half life of only 3 hours prevents its clinical application.

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. Promising results have been shown in certain patients with persistent diabetic macular edema receiving this intravitreal drug delivery system with improvement in visual acuity.

The present study introduces a novel concept of using intraoperative Ozurdex ® implant in patients with diabetes mellitus while undergoing cataract surgery to minimize the worsening of diabetic maculopathy.