Restricted accessResearch articleFirst published online 2011-11
Subthreshold Micropulse Diode Laser and Double Frequency Neodymium: YAG Laser in Treatment of Diabetic Macular Edema: A Prospective,Randomized Study Using Multifocal Electroretinography
Objective: The purpose of this study was to compare the efficacy of subthreshold micropulse diode (SDM) laser with double-frequency neodymium YAG (Nd:YAG) laser in treatment of clinically significant diabetic macular edema. Methods: Forty-six eyes of 33 patients with clinically significant macular edema (CSME) caused by diabetic retinopathy were randomized to either SDM (810 nm) laser or the conventional double-frequency Nd:YAG (532 nm) laser. Primary outcome measures were: change in the central macular thickness as measured by optical coherence tomography (OCT) and change in macular retinal sensitivity measured using multifocal electroretinography (MfERG). Secondary outcomes were: change in best corrected visual acuity (BCVA) and contrast sensitivity. Results: The group was divided in half, with 23 eyes assigned to SDM laser and 23 eyes assigned to double-frequency Nd:YAG laser. Mean follow-up period was 6 months. No statistically significant difference was noted in either the primary or the secondary outcome measures between the two groups. Macular thickness decreased from the baseline measures of 298.5±49.3 and 312.9±45.8 μm to 274.9±62.9 and 286.7±32.8 μm in the SDM laser and Nd:YAG laser groups, respectively. On MfERG, P1 implicit wave time delay at baseline changed from 46.27±4.9 to 45.27±3.4 ms in the SDM group and from 46.55±4.9 to 45.27±4.1 ms in the Nd:YAG group. MfERG recordings of 18 of the 23 eyes treated with double-frequency Nd:YAG laser showed areas of signal void as compared to 4 eyes treated with the SDM laser. Conclusions: SDM laser photocoagulation showed an equally good effect on visual acuity, contrast sensitivity, and reduction of diabetic macular edema (DME) as compared to conventional Nd:YAG laser photocoagulation. MfERG recordings, however, suggest that SDM laser results in better preservation of electrophysiological indices.
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