A randomized trial comparing the efficacy and safety of intravitreal triamcinolone with observation to treat vision loss associated with macular edema secondary to central retinal vein occlusion: the Standard Care vs Corticosteroid for Retinal Vein Occlusion (SCORE) study report 5

Retinal vein occlusion disease is estimated to be the second most common cause of retinal vascular disease in the United States.1 The prevalence of retinal vein occlusion in the Blue Mountains Eye Study was 1.6%, with 69.5%(41of59)oftheseocclusionsclassified as branch retinal vein occlusion (BRVO).2 Retinal vein occlusion was bilateral in 5.1% of cases.2 The 15-year cumulative incidence of BRVO was 1.8% in the Beaver Dam Eye Study.3 In the Beaver Damcohort,centraland branch retinal vein occlusion accounted for 12% of eyes that developed severe vision loss during a 15-year period.4 Macular edema is a frequent cause of visual acuity loss from BRVO.1,5,6 The natural history of macular edema secondary to BRVO was delineated in the Branch Vein Occlusion Study (BVOS).1 One arm of the BVOS demonstrated a benefit with grid photocoagulation.1 Of 43 treated eyes available for follow-up at the 3-year visit, 28 (65%) had gained 2 or more lines of visual acuity from baseline and maintained this gain for at least 8 months compared with the same gain in 13 of 35 untreated eyes (37%). The BVOS also identified a subset of patients who derived limited benefit from grid photocoagulation. In the BVOS, 40% of treated eyes (n=43) had worse than 20/40 visual acuity at 3 years, and 12% of treated eyes had 20/200 or worse visual acuity at 3 years.1 During the last decade, a number of additional treatments for macular edema secondary to BRVO have been investigated. Such treatments include laser chorioretinal anastomosis, vitrectomy, arteriovenous sheathotomy, and intravitreal injection of antibodies targeted at vascular endothelial growth factor (VEGF).7-12 Numerous reports have suggested that intravitreal injection(s) of triamcinolone acetonide (hereafter referred to as intravit-real triamcinolone) is a potentially efficacious therapy for retinal thickening and vision loss in patients with macular edema secondary to BRVO but that some patients may develop steroid-related complications, such as elevated intraocular pressure (IOP) and cataract.13-26 Most of the information concerning intravitreal triamcinolone for macular edema secondary to BRVO is derived from case series that lacked long-term follow-up and adequate numbers of study participants; a randomized and controlled study has not been performed.13-26 Despite the shortcomings of these case series, intravitreal triamcinolone is currently in use as a treatment for BRVO. The rationale for the use of corticosteroids to treat macular edema secondary to BRVO follows from the observation that the increase in retinal capillary permeability that results in macular edema may be caused by a breakdown of the blood-retina barrier mediated in part by VEGF, a 45-kDa glycoprotein.27-29 Therefore, attenuation of the effects of VEGF may reduce macular edema associated with BRVO.30,31 Corticosteroids have been demonstrated to inhibit the expression of VEGF and therefore may be an effective therapy for macular edema.32,33 Inflammation may also play a role in the pathology of BRVO, and the anti-inflammatory properties of corticosteroids may contribute to the attenuation of the disease process.34 Intravitreal triamcinolone is used by ophthalmologists in the clinical setting as a readily available pharmacologic agent (Kenalog 40; Bristol-Myers Squibb, Princeton, New Jersey, or Triesence; Alcon Inc, Fort Worth, Texas), though use for the treatment of macular edema is off label. Other formulations such as compounded preservative-free triamcinolone acetonide are also used in the clinical setting. The Standard Care vs Corticosteroid for Retinal Vein Occlusion (SCORE) Study, sponsored by the National Eye Institute, is a clinical trial designed to compare 1-mg and 4-mg doses of intravitreal triamcinolone with standard care for vision loss associated with macular edema secondary to per-fused central retinal vein occlusion (CRVO) and BRVO.35,36 This article describes findings from the SCORE-BRVO trial. A companion article that compares intravitreal triamcinolone with observation for vision loss associated with macular edema secondary to CRVO is published concurrently (the SCORE-CRVOtrial).37 The 2 primary study objectives of the SCORE-BRVO trial are (1) to determine whether intravit-real triamcinolone at 1-mg and 4-mg doses produces greater visual benefit, with an acceptable safety profile,than grid photocoagulation, when appropriate, for the treatment of vision loss associated with macular edema secondary to BRVO; and (2) to compare the efficacy and safety of the 1-mg and 4-mg triamcinolone doses.