Comparison of selective retinal laser and grid laser photocoagulation treatment efficacy in diabetic macular edema

OBJECTIVE: To investigate the efficacy of selective retina laser (SRL) in the treatment of diabetic macular edema (DME); comparing the effects of SRL on visual acuity and resolution of DME with conventional grid laser photocoagulation. MATERIAL AND METHOD: Ninetynine eyes of 84 patients with diabetic macular edema were enrolled in the study. The patients were divided into two groups. The first group was treated with the SRL and the second group was treated with grid laser photocoagulation. The patients were observed for 6 months. Detailed ophtalmological examination was done before and after the treatment, in the 1st week, 6th week, 3rd month and 6th month. Patients were evaluated by ophthalmoscopy, fluorescein angiography (FFA), best corrected visual acuity (BCVA) was measured by ETDS chart, macular edema index was evaluated by Heidelberg Retina Tomography (HRTII) and, fixation stability and mean retinal sensitivity within central 8º and 16º were measured by microperimetry (MP-1) at pretreatment, week 6, month 3 and 6. RESULTS: The differences of mean duration of diabetes mellitus, age, and sex between the groups were not statistically significant (p=0.083, p=0.053, p=0.069, respectively). In the SRL group mean logMAR BCVA was 0.52±0.35, 0.49±0.34, 0.48±0.34, 0.41±0.35 and 0.39±0.34 at pretreatment, week 1, week 6, month 3 and month 6, respectively. In the grid laser group mean logMAR BCVA was 0.53±0.31, 0.53±0.35, 0.50±0.33, 0.47±0.33 and 0.44±0.34 at pretreatment, week 1, 6, month 3 and 6, respectively. In the SRL group increase in vision at 3rd and 6th month after the treatment were statistically significantly compared to baseline measurements (p=0.002, p=0.000 respectively). An increase or stabilization of vision was determined at month 6 in 84.9% of patients in the SRL group. In the grid laser photocoagulation group increase in vision at month 6 after treatment was statistically significant compared to baseline measurements (p=0.003). An increase or stabilization of vision was determined at month 6 in 89.9% of patients in the grid laser photocoagulation group. Edema index was was 1.96±0.52, 1.53±0.46, 1.47±0.50 and 1.24±0.58 after SRL and of 2.08±0.4, 1.85±0.34, 1.66±0.31 and 1.41±0.39 after grid laser at pretreatment, week 6, month 3 and 6 respectively. In the SRL and grid laser photocoagulation group decrease in edema index at 6th month after the treatment was significantly different from baseline measurements (p=0.000, p=0.000 respectively). Mean retinal sensitivity at central 8 degree were 9.11±4.1, 9.02±4.2, 8.57±4.3 and 8.67±4.1 in the SRL group and 9.79±4.2, 8.43±4.6, 8.06±3.6 and 7.78±3.5 in the grid laser group at pretreatment, week 6, month 3rd and 6th respectively. No significant retinal sensitivity changed at month 3, month 6 after SRL treatment was seen (p=0.29, p=0.23 respectively) whereas statistically significant decrease was detected at month 3, month 6 after grid laser treatment (p=0.00 at month 3 and 6). Mean retinal sensitivity at central 16 degree were 9.95±3.8, 9.98±2.9, 10.31±4.2 and 9.49±3.9 in the SRL group and 11.06±4.8, 12.45±3.2, 10.04±3.2 and 9.39±4.4 in the grid laser group at pretreatment, week 6, month 3 and month 6 respectively. No significant change in retinal sensitivity (p=0.48 and 0.24 at month 3 and 6) after SRL and grid laser treatment (p=0.51 and 0.28 at month 3 and 6) was detected by MP-1. At month 6, FFA showed complete resolution of edema in 24 (45%) eyes and partial resolution of edema in 19 (36%) eyes in SRL group whereas 25 (57%) eyes showed complete resolution and 11 (23%) eyes partial resolution in the grid laser group. No complication such as choroidal neovascularisation, vitreous haemorrhage, subfoveal fibrosis and retinal detachment ocurred in both groups whereas atrophic scar spots due to laser treatment developed in all patients in the grid laser group. CONCLUSION: Treatment of DME by SRL was found to be as effective as grid laser photocoagulation with visual acuity, HRT-2 edema index and FFA. In the SRL group, preservation of the central 8° macular sensitivity may indicate that RPE is stimulated or damaged selectively without injury to neurosensorial retina. The low incidence of side effects and possiblity of repeated applications seem to be advantageous of SRL. Further clinical studies are warrented for evaluation of SRL effects precisely.