macular edema secondary to CRVO caused a significant decrease in macular edema but the VA did not improve in a randomized clinical trial. In that study, eyes with macular edema due to CRVO were randomized to macular grid photocoagulation (77 eyes) or no treatment (78 eyes) and followed every 4 months for 3 years or until the end of the study. This treatment clearly showed reduced macular edema on fundus fluorescein angiography at 1 year (69% of treated versus 0% of untreated eyes). However, there was no difference in VA between the treated (from 20/160 to 20/200) and untreated (from 20/125 to 20/160) eyes.42

Chorioretinal venous anastomosis

Chorioretinal venous anastomosis is used to bypass the occluded central retinal vein by creating a chorioretinal anastomosis between a nasal branch retinal vein and the choroidal circulation. Commonly, energy delivered via argon laser is directed at a branch retinal vein to rupture the posterior vein wall and Bruch’s membrane. Aretrospective consecutive series of 91 patients with nonischemic CRVO was conducted to evaluate the efficacy of and complications associated with laser-induced chorioretinal venous anastomosis and to identify the associated risks. When chorioretinal venous anastomoses were created in 49 eyes, 41 eyes had a 4.3 ± 3.8 line improvement in VA, 8 eyes had no improvement or reduced vision, and 18 eyes had neovascular complications.43

In another report of a consecutive series of 8 cases with nonischemic CRVO, successful chorioretinal venous anastomoses were created in 2 eyes, 2 patients had improved VA without a successful treatment, and 6 patients had unchanged or worsened VA. The complications included retinal neovascularization in 3 patients, vitreous hemorrhage in 3 patients, subsequent iris neovascularization in 3 patients, tractional retinal detachment in 2 patients, and neovascular glaucoma in 1 patient.44 The complications of this technique included immediate internal, subretinal, or vitreous hemorrhage; the long-term complications included vitreous hemorrhage, epiretinal avascular proliferation, fibrovascular proliferation, secondary neovascularization, and tractional retinal detachment. Because some studies reported an increased risk of fibrovascular complications in eyes with ischemic CRVO, laser chorioretinal anastomosis is not recommended for ischemic CRVO.43,44

SURGICAL TREATMENT OF CRVO

Radial optic neurotomy (ron)

Opremcak and colleagues hypothesized that CRVO is neurovascular compartment syndrome at the site of the lamina cribrosa. RON, a procedure developed by those investigators, decompresses the scleral outlet via an internal vitreoretinal approach using a radial incision nasal to the optic nerve head.45 In a report of 117 consecutive cases by Opremcak and colleagues, the Snellen VA improved an average of 2.5 lines in 71% of patients; clinical improvement on fundus examination, fundus photography, and fluorescein angiography was seen in 95%.46 Postoperatively, chorioretinal anastomosis at the incision site may facilitate more active drainage of retinal edema and hemorrhage compared to laser-induced chorioretinal anastomosis. However, a postoperative visual field defect has been reported, and the potential risk of subintraretinal or vitreous hemorrhage may be problematic.47

Branch retiNAL vein occlUSION

Corticosteroids

The effects of intravitreal injection of TA for macular edema secondary to BRVO have been reported (Figure 20.6). Numerous reports suggested that intravitreal injection had the potential to improve vision loss and retinal thickening in patients with macular edema associated BRVO, but suggested that some patients developed steroid-related complications such as elevated intraocular pressure (IOP) and cataract; injection-related complications such as retinal detachment and endo- phthalmitis.10,48–59 The Standard Care vs Corticosteroid for Retinal Vein Occlusion (SCORE) was multicenter, randomized, clinical trial of 411

participants to compare the efficiency and safety of 1-mg 4-mg doses of preservative-free intravitreal triamcinolone with grid photocoagulation for eyes with macular edema secondary to BRVO. The primary outcome in this study, the percentage of participants with a gain in visual acuity letters score of 15 or more from baseline to month 12, was 29%, 26%, and 27% for the observation, 1-mg, and 4 mg respectively. This trial concluded that there was no significant difference in terms of visual acuity outcomes among the groups treated with grid photocoagulation, 1-mg of intravitreal triamcinolone, or 4-mg of intravitreal triamcinolone for macular edema secondary to BRVO at 12 months and grid photocoagulation had a safety profile superior to intravitral triamcinolone with respect to the potential for added risks of procedurerelated complications.60

Bevacizumab

Intravitreal injection of bevacizumab was also used to treat macular edema due to BRVO (Figure 20.7). Twenty-seven consecutive patients withBRVOweretreatedwithintravitrealbevacizumab(1.25mg/0.05ml) for macular edema secondary to BRVO. The mean VA improved from 20/200– at baseline to 20/100+ at 3 months and, at the last follow-up visit, the mean central 1-mm macular thickness of 478 m at baseline decreased to 336 at 3 months and 332 m at the last follow-up visit.13 There were no significant differences in the number of injections or the anatomic and visual outcomes 6 months after injection of two different doses (1.25 and 2.5 mg) of intravitreal bevacizumab in 45 patients with macular edema secondary to BRVO.14

Ranimizumab

Intravitreal injection of ranibizumab was also used to treat macular edema secondary to BRVO.61 BRAVO is a multicenter, randomized, double-masked, sham injection-controlled Phase III study of 39 participants designed to assess the efficiency and safety profile of ranimizumab for macular edema associated to BRVO. The month 6 result showed that 55.2% (74/132) of patients received 0.3 mg of ranimizumab and 61.1% (80/131) received 0.5 mg of ranimizumab had their vision improved by 15 letters or more compared to 28.8% (38/130) of patients receiving sham injections and mean gain was observed beginning at day seven with an 7.6 and 7.4 letter gain in the 0.3 mg and 0.5 mg study arms of ranimizumab, respectively, compared with 1.9 letters in the sham injection arm.33

Laser treatment

The Branch Vein Occlusion Study, a multicenter, randomized, controlled trial supported by the National Eye Institute and the Branch Vein Occlusion Study Group, evaluated if grid macular laser photocoagulation improves VA in eyes with 20/40 or worse vision resulting from macular edema secondary to BRVO. A total of 139 eligible eyes were randomized to either the treated or the untreated control group. The mean VA for patients treated with grid laser was 20/40 to 20/50 compared with 20/70 for the control group (mean follow-up, 3.1 years). Treated patients gained an average of 1.33 lines of VA after 3 years from baseline compared with 0.23 line in the control group. The grid laser group had a significant improvement in VA and gained 2 lines or more of vision over consecutive visits (65% of treated eyes versus 36% of control eyes).62

SURGICAL TREATMENT OF BRVO

The obstruction site in BRVO is almost always at an arteriovenous crossing site with the common adventitial sheath of the overlying arteriole and the underlying venule. Removing the compressive factor by sheathotomy may be an effective treatment for BRVO.63 Osterloh and Charles reported a significant improvement in VA (from 20/200 to 20/25+) over 8 months in the first report of sheathotomy.64 Mason et al. reported a prospective comparison of 20 eyes treated with vitrectomy and sheathotomy with 20 control eyes (10 observed eyes and 10 lasertreated eyes). In that report, sheathotomy resulted in a significantly better visual outcome (20/250 mean VA at baseline to 20/63 after

Pharmacotherapy to Amenable Diseases Retinal • 3 section