Optical Coherence Tomography Angiography Changes After Subthreshold Micropulse Yellow Laser in Diabetic Macular Edema

Abstract

Purpose: To assess changes on optical coherence tomography (OCT) angiography in diabetic macular edema (DME) treated with subthreshold micropulse yellow laser (SMPL) over a period of 6 months. Methods: Thirty-five eyes (35 consecutive patients) with treatment-naive DME prospectively underwent (at baseline, 3 and 6 months) best-corrected visual acuity, swept-source OCT angiography/OCT, and fundus autofluorescence. Following parameters were evaluated on OCT angiography in the superficial capillary plexus (SCP) and deep capillary plexus (DCP): the area of foveal avascular zone, number of microaneurysms (MA), area of cysts, and presence of capillary network alterations. Microaneurysm change was also evaluated in 15 fellow eyes, not needing treatment over 6 months. Vessel and perfusion densities were evaluated in the SCP, DCP, and choriocapillaris, with image J. Retina thickness, number of hyperreflective retinal spots, and external limiting membrane integrity were evaluated on OCT. All measurements were performed by two masked graders, independently. Results: All patients had diabetes mellitus Type 2 (mean age, 69.4 ± 10.9 years; duration of diabetes mellitus, 15.7 ± 8.7 years; and HbA1c 7.7 ± 1.2%). Mean best-corrected visual acuity at baseline was 69.7 ± 12.0 letters ETDRS, 72.7 ± 10.7 at 3 months (gain 3.1 ± 4.3, P = 0.0049) and 74.3 ± 9.5 at 6 months (gain 4.6 ± 7.2, P < 0.0001). Foveal avascular zone area decreased in the DCP at 6 months (P = 0.01). Area of cysts decreased in the SCP at 3 months and 6 months (P = 0.038; P = 0.049), and in the DCP at 6 months (P = 0.0071). Number of MA decreased at 6 months in the SCP (P = 0.0007) and at 3 months and 6 months in the DCP (P = 0.048; P < 0.0001) in treated eyes. No significant change in number of MA was found in nontreated eyes. There was no statistically significant change in any other OCT angiography/OCT parameter. Conclusion: Subthreshold micropulse yellow laser induces more pronounced changes in the DCP than in the SCP in DME. These changes occurred as early as 3 months after treatment. The evaluation of specific parameters in the DCP may help in determining treatment response.

Subthreshold Micropulse Laser in Diabetic Macular Edema: 1-Year Improvement in OCT/OCT-Angiography Biomarkers

“…19,20 However, the RPE has been considered the main target of SMPL with consequent modifications of retinal cells' metabolic activity and changes of gene expression and protein secretion. 1,2,17,18 As the present study was not designed to evaluate the anatomic target of SMPL, we could only speculate on a possible effect on GLC through reduction of HRS and MA in the DCP. 18 Further studies are needed to confirm this hypothesis and determine whether this action is direct on GLC or indirect through the stimulation of RPE.…”

“…To the best of our knowledge, only one previous study (from our group), using a different cohort of patients with DME and with shorter follow-up, evaluated the use of OCTA to investigate the clinical effects of SMPL, documenting earlier and more pronounced changes in some macular parameters (FAZ area, number of MAs, and area of the cysts) in the DCP than in the SCP up to 6 months after treatment. 18 DR is a complex multifactorial disease, in which inflammation plays an important role. 26,27 Several noninvasive imaging biomarkers of inflammation in the retina have been studied in patients with DR and DME.…”

“…The characteristics of this device have been previously described in detail. 18 The following scans were acquired: single 6-mm high-definition B-scan at 0 degrees and 90 degrees, 6mm radial OCT scan (consisting of 12 scans 15 degrees apart) centered on the fovea, and 3-dimensional 3 × 3 mm OCTA map of the macula.…”

“…All OCTA images were carefully reviewed to check automatic segmentation of different slabs, with particular attention to DCP and CC segmentation, as previously reported. 18 MAs were manually counted on OCTA slabs using the reverse mode (black vessels on white background) allowing a better visualization. 11 The area of the cysts was measured after manually delimiting the contours of single retinal cysts in the SCP and DCP using the caliper tool implemented in the machine software IMAGENET 6 (version 1.17.9720).…”

“…16,17 This stress-induced response results in the immunomodulation of retinal cells metabolism and function, activation of repair processes, and decrease in the production of inflammatory cytokines, vascular endothelium growth factor (VEGF), and matrix metalloproteinases. 1,2,17,18 Recently, it has been reported that SMPL reduces the aqueous humour (AH) concentration of inflammatory cytokines secreted by retinal glial cells (GLCs), both Müller cells (MCs) and microglial cells (MGCs) in eyes with DME. 19,20 A decrease in the inner nuclear layer thickness (INL), where the bodies of MCs are located, was reported after SMPL.…”