Subthreshold Laser Photocoagulation using a Conventional Pattern Scan Laser to Treat Macular Edema

Abstract

Purpose : We previously reported the efficacy of subthreshold laser photocoagulation (SLP) using a general pattern scan laser to treat macular edema (ME) caused by ischemic retinal diseases (11 eyes of 11 patients, European Society of Ophthalmology, 2017). The present study examined the treatment effects of SLP, and included more cases and a longer observation period.

Methods : We assessed the effects of SLP treatment in 24 eyes of 24 patients with ME. Seventeen patients had diabetic retinopathy, five had branch retinal vein occlusion, and two had central retinal vein occlusion. All patients underwent SLP treatment between December 2015 and May 2017. The average postoperative observation period was 5.5 ± 3.4 months. We evaluated the following parameters before the SLP procedure and at one, two, and three months postoperative: best-corrected visual acuity using logMAR scores, center macular thickness (CMT), and total macular volume (TMV) as determined by optical coherence tomography (OCT). We fixed the 577-nm laser beam of a scanning laser photocoagulator at an area 100 μm in diameter, 20ms, and selected a 2 × 2 grid scan pattern using an Area Centralis^® lens. The initial laser power of the SLP was 100 mW, and the laser was focused on a specific area of the ME identified by OCT. If spot lesions were visible on ophthalmoscopic examination, the laser power was decreased by 10 mW to avoid scarring.

Results : The laser power was 76.7 ± 18.1 (50-100) mW and the total laser shots were 374.4 ± 243.9. The preoperative logMAR scores and TMV were 0.26 ± 0.32 and 9.7 ± 1.6 mm³, respectively. They were 0.28 ± 0.29 and 9.6 ± 3.1 mm³, at one month postoperative, 0.25 ± 0.32 and 9.6 ± 2.6 mm³, at two months, and 0.25 ± 0.31 and 9.3 ± 1.7 mm³ at three months. A significant reduction in TMV was observed at three months postoperative (P < 0.01), and the CMT had decreased by ≥ 20% in 10 of 24 eyes (41.7%) three months after SLP treatment. The TMV remained significantly decreased in 7 eyes that were observed for nine months postoperatively.

Conclusions : These findings suggest that SLP using a general pattern scan laser for the treatment of ME is effective over a long period of time.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.