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

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 (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.

Inclusion criteria

The patients of Type 2 Diabetes Mellitus fulfilling the following inclusion criteria shall be enrolled in the study:

• Presence of visually significant cataract requiring surgery (any grade)
• Patients with Non-proliferative Diabetic Retinopathy (NPDR) with/without clinically significant macular edema (CSME)
• Patients with Proliferative Diabetic Retinopathy (PDR) with/without CSME where proliferative component has been adequately treated with laser photocoagulation.

All patients fulfilling criteria 1 with 2 or 3 shall be enrolled in the study. The patients of either sex up to the age of 60 years would be included for the study.

Exclusion criteria

The following would be the exclusion criteria:

• Presence of untreated proliferative diabetic retinopathy
• Patients with history of ocular hypertension or glaucoma
• Presence of associated conditions that may exacerbate macular edema, i.e. uveitis, retinal vein occlusions, neovascular glaucoma
• History of use of drugs such as prostaglandin analogues, adrenaline or nicotinic acid
• Patients with post-operative media haze or pupillary non-dilation that does not allow good fundus photography, Fundus Fluorescein Angiography (FFA) and Optical Coherence Tomography (OCT).
• Patients who develop any intraoperative complication including posterior capsular rent, vitreous loss, zonular dehiscence, etc shall be excluded from the study in both the groups