Subthreshold 577 nm laser photocoagulation vesus conventional 532 nm laser photocoagulation for diabetic macular oedema

Abstract

Purpose: To evaluate the visual and anatomic outcomes of the subthreshold micropulse 577 nm yellow diode laser (MYL) and to compare its efficacy with the conventional green 532 nm diode laser (CGL) in Asian eyes with diabetic macular oedema (DME).
Study design: Prospective randomized controlled clinical trial
Methods: Sixty-seven eyes of 43 patients with clinically significant macular oedema (CSME) were randomized to receive either MYL (n = 37) or CGL (n = 30) at baseline and were followed up for 12 months. Titration in the MYL group was performed with 15% duty cycle, 300 ms duration, and double the threshold power, while the modified Early Treatment of Diabetic Retinopathy Study (mETDRS) protocol was used for the CGL arm with the power titrated to a barely visible burn. Parameters noted included best-corrected visual acuity (BCVA) (logMAR), central subfoveal thickness (CST), macular volume (MV), and average macular thickness (AMT) using optical coherence tomography, and presence of visible laser scars on colour fundus photographs and fundus autofluorescence, at baseline and at 12 months.
Results: At 12 months follow-up, BCVA improved by 4.7 and 8.8 letters, respectively, for the MYL and CGL treatment arms (p < 0.05). There was a significant reduction in all retinal thickness parameters (CST, MV, and AMT) when compared to baseline in both laser treatment arms at 12 months. There was no significant difference in either BCVA or retinal thickness parameters between the two treatment arms at 1, 3, 6, 9, or 12-month follow-up. Laser scars were observed in 26.7% of patients in the MYL group compared to 75% of patients in the CGL group (p = 0.029).
Conclusions: MYL is an effective, safe, and patient-friendly treatment option for clinically significant macular oedema, with improvement in BCVA, reduction in macular thickness, and less scarring after treatment at 12 months.