Intravitreal injection versus subtenon's infusion of triamcinolone acetonide for refractory diabetic macular edema during phacoemulsification

• Grant number: 05/04508-2
• Support Opportunities: Regular Research Grants
• Start date: October 01, 2006
• End date: November 30, 2007
• Field of knowledge: Health Sciences - Medicine
• Principal Investigator: Rodrigo Jorge
• Grantee: Rodrigo Jorge
• Host Institution: Faculdade de Medicina de Ribeirão Preto (FMRP). Universidade de São Paulo (USP). Ribeirão Preto , SP, Brazil

Abstract

Triamcinolone is considered to be an effective and safe agent when applied to the subtenonian space and to the intravitreous cavity for the treatment of pathologic conditions that require a prolonged period of steroid administration, such as uveitis, macular edema secondary to retinal vascular diseases, and intraocular proliferation such as proliferative vitreoretinopathy and choroidal neovascularization. In addition, it is a steroid with hydrophobic characteristics, a fact that confers a prolonged time of action on it compared to other corticosteroids. Macular edema is the main cause of reduced visual acuity in diabetic patients. Until recently, the only treatment of proven efficacy was photocoagulation with LASER applied focally or in a grid manner. However, 24% of the eyes treated suffer reincidence and/or persistence of retinal thickening a period of 36 months after the procedure. The diagnosis of clinically significant diabetic macular edema is made by biomicroscopy and a diagnosis of treatable macular edema is made according to the standards defined by the Early Treatment Diabetic Retinopathy Study. Although technological advances have caused fluorescein angiography to be a method potentially very useful for the detection of retinal edema and for its qualitative evaluation (degree of contrast extravasation), the method does not define the anatomical details of the neurosensory retina involved by edema, among them the thickness of the layers involved. Optic coherence tomography (OCT) is a noninvasive non-contact imaging method that can produce semi-histological images of the human retina by means of setional cuts with a resolution of 10-15 μm. Thus, the physiological aspect of the clinically significant macular edema is evaluated by fluorescein angiography, whereas the anatomical aspect of edema, including its extent, the presence of vitreous traction and the retinal layer involved can be measured reliably only by OCT. In view of the current availability of new therapeutic modalities such as subtenonian and intravitreous injection of corticosteroids and vitrectomy for the treatment of EMCS, the correlation between the anatomical and physiological condition of the retina has become important for the detection, indication of the best treatment mode and follow-up of diabetic macular edema4.Corticosteroids have been used for decades in ophthalmology to suppress intraocular inflammation and to reduce vascular estravasation. In an attempt to prevent the adverse systemic effects of steroids while at the same time providing high cortisone concentrations at the site of action, today corticosteroids are injected directly into the vitreous cavity or in direct contact with the posterior sclera (subtenonian) with promising results for the treatment of various diseases. In Brazil, treatment with triamcinolone by the subtenonian and intravitreous routes is becoming universally accepted through its use, as is also the case in the United States and in Europe. The diffuse use of this corticoid is based on various published reports that have demonstrated the safety and efficacy of these methods. To date, no comparative study has been published regarding the most effective route and dose of triamcinolone to be administered during phacoemulsification surgery for the treatment of CSME refractory to treatment with LASER in diabetics with cataracts. A recent study by our group demonstrated that intravitreous injection of triamcinolone is more effective than subtenonian infusion of 40 mg for the reduction of retinal thickness and for the improvement of visual acuity in phacic patients. As a continuation of this line of investigation, we intend to evaluate the efficacy and complications of subtenonian injection of triamcinolone compared to intravitreous injection immediately after the end of surgery for cataracts in patients with significant macular edema refractory to standard treatment with LASER. (AU)