Abstract
Purpose :
Diabetes causes release of various inflammatory and angiogenic cytokines, glycosylation causes cell damage and structural changes in blood vessels resulting in microaneurysms and abnormal leaky blood vessels that give rise to CSME. According to ETDRS the risk of development of vision impairment is decreased to 50 % after laser photocoagulation. Laser reduces central subfield thickness (CST) and cause some improvement in visual acuity (VA). However, the disadvantage of threshold Laser photocoagulation is scarring/chorioretinal atrophy, scotoma, and visual field defects. With Topcon Pattern Scanning Laser (PASCAL) system streamline yellow it is possible to calculate and apply the sub threshold energy required to stimulate retinal cells without causing damage to photoreceptors and retinal pigment epithelium (RPE). It applies low power density over large spot size and longer pulse to achieve non damaging end point.
Stimulation of retinal pigment epithelial cells causes formation of heat shock proteins that act as chaperones causing refolding of misfolded proteins, prevent apoptosis and down regulate inflammation, improve RPE function, thereby facilitating absorption of macular edema. The absence of retinal scarring and damage can be evidenced on FAF images.
Methods :
We included the 21 eyes of pts. having clinically significant diabetic macular edema (CSME) without ischemia in our study.
Baseline VA measurement, OCT, FAF and fluorescein angiography were done in all patients.
The PASCAL streamline yellow laser was used to apply barely visible burn in mid periphery of retina, then the energy was titrated to 30 percent and subthreshold treatment applied over the CSME in a doughnut shape pattern, with spot size 200 µ, max power 200 mW, duration 15 ms. Pt were followed up after 1, 4 and 12 weeks. VA, FAF and OCT acquisition were done on each visit.
Results :
Improvement in CST was seen in 71.4% eyes, 14.2% eyes developed recurrent macular edema after initial improvement and needed retreatment and 14.2% eyes showed no improvement, VA improved in 66.6%, stable in 23.8% and worsened in 9.5% .
Conclusions :
EPM with subthreshold laser is a safe and effective way of improvement of CST and VA in CSME. It may reduce the treatment sessions with faster resolution of macular edema if used as an adjunct to intravitreal injections or as a rescue treatment.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.