Retina anti-inflammatory response after subthreshold micropulse laser in diabetic macular edema:OCT and OCT-angiography study

Abstract

Purpose : To evaluate one-year changes in inflammatory and microvascular macular parameters after subthreshold micropulse laser(SMPL) in diabetic macular edema(DME) by means of optical coherence tomography(OCT) and OCT-angiography(OCT-A).

Methods : Thirty-seven eyes/patients with previously treatment-naïve DME and treated with SMPL were retrospectively evaluated at 3, 6 and 12 months. Fifteen fellow eyes with microaneurysms(MA) not requiring any treatment were the control group. Main inclusion criteria were:previously treatment-naïve DME with central macular thickness(CMT)≤400 μm and good image quality. SMPL was performed with a subthreshold(577-nm) yellow micropulse laser using standard setting. OCT parameters included: CMT; number of hyper-reflective retinal spots(HRS, sign of activated microglia). On 3x3 mm OCT-A images: number of MA, cysts area and perfusion density(using Matlab for artifacts removal) at the superficial and deep capillary plexuses(SCP/DCP). Changes over time of quantitative variables were evaluated by means of analysis of variance for repeated measures(ANOVA). Differences in treated patients at different follow-ups were assessed with two-tails t-test for dependent variable.

Results : Mean BCVA in the treated group improved from 69.5±12.0 ETDRS letters at baseline to 76±9.1 at 12 months(p=0.004). Mean CMT decreased without reaching statistical significance. A decrease in number of HRS(p<0.01) and MA in DCP(p=0.015) was detected at 3, 6 and 12 months after SMPL. MA in SCP(p<0.01) and cysts area in SCP and DCP(p<0.01) decreased at 6 and 12 months after SMPL. In the control group HRS and MA remained stable over time and different (p<0.001) vs treated eyes. No significant changes were found in macular perfusion parameters. Mean number of SMPL treatments was 2.2±0.74 in 12 months.

Conclusions : SMPL proved to be effective in determining a decrease in HRS, MA and cysts area over a period of 12 months, starting as early as 3 months for HRS and MA in DCP. The exact mechanism of action of SMPL is still under investigation. The results of this study may suggest an early anti-inflammatory effect of SMPL proven by a measurable improvement in HRS number and DCP morphology. Further studies are needed to confirm these data and evaluate the main site of action of SMPL.

This is a 2020 ARVO Annual Meeting abstract.