The impact of central foveal thickness on the efficacy of subthreshold micropulse yellow laser photocoagulation in diabetic macular edema

To evaluate the efficacy of short-term subthreshold micropulse yellow laser photocoagulation (SMYLP) on eyes with diabetic macular edema (DME) with different central foveal thicknesses (CFT). Eighty eyes of 40 patients who had previously undergone ranibizumab treatment for DME and who subsequently had recurrent macular edema were included to the study. The study subjects were divided into four groups according to their initial CFT values (group 1, 250–300 μm; group 2, 301–400 μm; group 3, > 401 μm; group 4, 250–300 μm untreated control subjects). Patients were treated with SMYLP for one session and followed for 6 months. All patients underwent complete ophthalmologic evaluation. The alteration from baseline in CFT and the best corrected visual acuity (BCVA) were measured. Patients with a pretreatment CFT ≤ 300 μm experienced the statistically significant reduction in CFT and gain in BCVA at 2 months (p < 0.05), whereas patients with baseline CFT > 300 μm experienced no significant change (p > 0.05). Hyperautofluorescence lesions, that were not previously described, were detected in fundus autofluorescence imaging in the early period after SYMLP laser and these lesions were regressed with time. Our study indicates that the SYMLP provides a statistically significant improvement in BCVA and a reduction in CFT in the patients with a pretreatment CFT of 300 μm or less in DME and can be safe and effective in mild DME treatment.