COMPARISON OF SUBTHRESHOLD MICROPULSE DIODE LASER PHOTOCOAGULATION WITH CONVENTIONAL LASER PHOTOCOAGULATION FOR CLINICALLY SIGNIFICANT MACULAR EDEMA IN DIABETIC PATIENTS.

Abstract

Abstract: : Purpose:To report updated results of a study that compares Subthreshold Micropulse Diode Laser Photocoagulation (SMDLP) to Conventional Argon Laser Photocoagulation (CLP) for the treatment of diabetic clinically significant macular edema (CSME) in 23 eyes presented last year (IOVS 44, 2003). Methods: An ongoing prospective pilot study involving diabetic patients with CSME randomized into two groups – SMDLP and CLP groups. Twenty–three eyes of 19 diabetic phakic patients have been included in the study. Mean follow up period – 11 months. CSME was defined as per ETDRS criteria. Best–corrected visual acuity (BCVA) was measured with ETDRS chart and converted to logMAR. Evaluation of CSME was based on clinical evaluation, fluorescein angiogram and optical coherence tomography. The laser settings in SMDLP group were: spot size 75µm, micropulse mode 5%–15% (burn duration 0.1–0.3 msec, interval duration 1.7–1.9 msec), envelope duration 150–400 msec, power 600 to 1500 mW and number of burns ranged from 14 to 410. The laser settings in CLP group were: spot size 50 – 100 µm, duration 50–75 msec, power 80 to 140 mW and number of burns ranged from 26 to 204. Results: Twelve eyes received SMDLP and 11 eyes received CLP. Mean follow up period was 12 months in SMDLP group and 10 months in CLP group. As a result of the treatment, CSME was resolved in 75% of eyes in SMDLP group (average number of treatments– 1.8) and in 72.7% of eyes in CLP group (average number of treatments – 1.85). At baseline, mean BCVA in SMDLP and CLP was 0.1 and 0.1 logMAR respectively. At the last follow up visit, mean BCVA in SMDLP and CLP was 0.17 and 0.18 logMAR respectively. Final BCVA in SMDLP group remained unchanged in 11 (92%) eyes and worsened by 3 or more lines on ETDRS chart in 1 (8%) eye. In CLP group, the final BCVA remained unchanged in 9 (82%) eyes and worsened in 2 (18%) eyes. Visual field testing revealed post treatment new scotomas in 2 out of 12 eyes (17%) treated with SMDLP and in 2 out of 11 eyes (18%) treated with CLP. Baseline average retinal thickness/volume (within 3.45 mm of the center of the fovea) in eyes with CSME were 305±82 mic/2.83±0.7 mm³ and 286±45 mic/2.8 ± 0.4 mm³ in SMDLP and CLP respectively. Among eyes with resolved CSME, retinal thickness/volume were 250±33 mic/2.38±0.34 mm³ in SMDLP group vs 219±18 mic/2.25±0.14 mm³ in CLP group. Conclusion: SMDLP is beneficial in the treatment of CSME in diabetic patients. Results of a larger series of patients are underway.

Keywords: clinical (human) or epidemiologic studies: systems/equipment/techniques • laser • diabetic retinopathy