Comparative efficacy of pure yellow (577-nm) and 810-nm subthreshold micropulse laser photocoagulation combined with yellow (561-577-nm) direct photocoagulation for diabetic macular edema

Abstract

Purpose: To compare the efficacy of 577- and 810-nm subthreshold micropulse laser photocoagulation (SMLP) combined with direct photocoagulation to microaneurysms in diabetic macular edema (DME).

Methods: A prospective nonrandomized interventional case series. Forty-nine consecutive patients (53 eyes) with DME were recruited. In 20/24 (83.3%) eyes, 810-nm SMLP (810-nm MP) to achieve a confluent grid pattern was followed by direct photocoagulation to microaneurysms via a continuous 561-nm wavelength laser. In 21/29 (72.5%) eyes, 577-nm SMLP (577-nm MP) was combined with direct photocoagulation to microaneurysms via the same instrument. Best-corrected visual acuity (BCVA) and central macular thickness (CMT) were examined 1, 2, 3, 6 and 12 months after treatment.

Results: The mean power required for SMLP was lower in the 577-nm than in the 810-nm MP group (204.1 vs. 954.1 mW) (p < 0.0001). Significant reductions in CMT persisted from 3 to 12 months after treatment in all patients (p < 0.01). There were no significant intergroup differences in CMT until 12 months. In both groups, mean BCVA remained stable until 12 months after treatment. Additional treatment for persistent macular edema was performed within 12 months in 4/24 eyes (16.7%) in the 810-nm MP group and 1/29 eyes (3.4%) in the 577-nm MP group.

Conclusion: Either 577-nm MP or 810-nm MP combined with direct photocoagulation for microaneurysm closure reduced DME, maintained visual acuity and reduced the additional treatment rate within 12 months. The 577-nm MP apparatus required less energy for SMLP than the 810-nm MP instrument and was suitable for direct photocoagulation of microaneurysms.