Factors affecting the response to subthreshold micropulse laser therapy used in center-involved diabetic macular edema.

The purpose of this study was to investigate the effect of the status of retinal pigment epithelium (RPE) and HbA1c levels on the efficacy of the subthreshold micropulse laser (SMPL) in the treatment of center-involving diabetic macular edema (DME). A total of 20 eyes of 20 patients (mean age 57.9 ± 9.7 years) who were diagnosed with center-involving DME and treated with SMPL for refusing intravitreal injection and 20 eyes of 20 age- and sex-matched healthy participants were enrolled. All patients were followed up in the 1st and 3rd months after SMPL. For measurement of RPE area central 1000 microns, macular EDI-OCT scans were binarized by using the public domain software ImageJ, with a semi-automated technique. There was a significant increase in BCVA values and a significant decrease in CMT values during follow-up. The area of RPE before SMPL was significantly thinner in the patient group (p: 0.004). When the areas of RPE before and 3 months after SMPL were compared, no significant change was observed (p: 0.437). When the relationship between pre-treatment area of RPE and HbA1c was examined, an inverse correlation was observed (p: 0.018). The patients were evaluated by dividing them into 2 groups as 2nd session SMPL required and not required, and the area of RPE was smaller in the group requiring 2nd session SMPL (p: 0.030). The status of central RPE may be a determining factor on the response to treatment. Additionally, HbA1c levels may have an impact on treatment efficacy.