Macular grid laser photocoagulation for branch retinal vein occlusion.

BACKGROUND: Branch retinal vein occlusion (BRVO) is the second most common cause of retinal vascular abnormality after diabetic retinopathy. Persistent macular oedema develops in 60% of eyes with a BRVO. Untreated, only 14% of eyes with chronic macular oedema will have a visual acuity (VA) of 20/40 or better. Macular grid laser photocoagulation is used for chronic non-ischaemic macular oedema following BRVO and has been the mainstay of treatment for over 20 years. New treatments are available and a systematic review is necessary to ensure that the most up-to-date evidence is considered objectively.

OBJECTIVES: To examine the effects of macular grid laser photocoagulation in the treatment of macular oedema following BRVO.

SEARCH METHODS: We searched CENTRAL, Ovid MEDLINE, EMBASE, Web of Science Conference Proceedings Citation Index, the metaRegister of Controlled Trials (mRCT), ClinicalTrials.gov and the WHO International Clinical Trials Registry Platform. We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 21 August 2014.

SELECTION CRITERIA: We included randomised controlled trials (RCTs) comparing macular grid laser photocoagulation treatment to another treatment, sham treatment or no treatment.

DATA COLLECTION AND ANALYSIS: We used standard methodological procedures expected by Cochrane.

MAIN RESULTS: We included five studies conducted in Europe and North America. Four separate trials compared grid laser to no treatment, sham treatment, intravitreal bevacizumab and intravitreal triamcinolone. One further trial compared subthreshold to threshold laser. Two of these trials were judged to be at high risk of bias in one or more domains.In one trial of grid laser versus observation, people receiving grid laser were more likely to gain visual acuity (VA) (10 or more ETDRS letters) at 36 months (RR 1.75, 95% confidence interval (CI) 1.08 to 2.84, 78 participants, moderate-quality evidence). The effect of grid laser on loss of VA (10 or more letters) was uncertain as the results were imprecise (RR 0.68, 95% CI 0.23 to 2.04, 78 participants, moderate-quality evidence). On average, people receiving grid laser had better improvement in VA (mean difference (MD) 0.11 logMAR, 95% CI 0.05 to 0.17, high-quality evidence). In a trial of early and delayed grid laser treatment versus sham laser (n = 108, data available for 99 participants), no participant gained or lost VA (15 or more ETDRS letters). At 12 months, there was no evidence for a difference in change in VA (from baseline) between early grid laser and sham laser (MD -0.03 logMAR, 95% confidence interval (CI) -0.07 to 0.01, 68 participants, low-quality evidence) or between delayed grid laser and sham laser (MD 0.00, 95% CI -0.04 to 0.04, 66 participants, low-quality evidence).The relative effects of subthreshold and threshold laser were uncertain. In one trial, the RR for gain of VA (15 or more letters) at 12 months was 1.68 (95% CI 0.57 to 4.95, 36 participants, moderate-quality evidence); the RR for loss of VA (15 or more letters) was 0.56 (95% CI 0.06 to 5.63, moderate-quality evidence); and at 24 months the change in VA from baseline was MD 0.07 (95% CI -0.10 to 0.24, moderate-quality evidence).The relative effects of macular grid laser and intravitreal bevacizumab were uncertain. In one trial, the RR for gain of 15 or more letters at 12 months was 0.67 (95% CI 0.39 to 1.14, 30 participants, low-quality evidence). Loss of 15 or more letters was not reported. Change in VA at 12 months was MD 0.11 logMAR (95% CI -0.36 to 0.14, low-quality evidence).The relative effects of grid laser and 1mg triamcinolone were uncertain at 12 months. RR for gain of VA (15 or more letters) was 1.13 (95% CI 0.75 to 1.71, 1 RCT, 242 participants, moderate-quality evidence); RR for loss of VA (15 or more letters) was 1.20 (95% CI 0.63 to 2.27, moderate-quality evidence); MD for change in VA was -0.03 letters (95% CI -0.12 to 0.06, moderate-quality evidence). Similar results were seen for the comparison with 4mg triamcinolone. Beyond 12 months, the visual outcomes were in favour of grid laser at 24 months and 36 months with people in the macular grid group gaining more VA.Four studies reported on adverse effects. Laser photocoagulation appeared to be well tolerated in the studies. One participant (out of 71) suffered a perforation of Bruch's membrane, but this did not affect visual acuity.

AUTHORS' CONCLUSIONS: Moderate-quality evidence from one RCT supports the use of grid laser photocoagulation to treat macular oedema following BRVO. There was insufficient evidence to support the use of early grid laser or subthreshold laser. There was insufficient evidence to show a benefit of intravitreal triamcinolone or anti-vascular endothelial growth factor (VEGF) over macular grid laser photocoagulation in BRVO. With recent interest in the use of intravitreal anti-VEGF or steroid therapy, assessment of treatment efficacy (change in visual acuity and foveal or central macular thickness using optical coherence tomography (OCT)) and the number of treatments needed for maintenance and long-term safety will be important for future studies.