Pan-Retinal Photocoagulation Safety Profile Comparison Of Single-Session Patterned Scan Laser With Multiple-Session 532nm Nd:YAG Laser In Proliferative Diabetic Retinopathy

Rajvardhan Azad

Purpose: Single-session(SS) pan-retinal photocoagulation(PRP) for proliferative diabetic retinopathy(PDR) with current 532nm Nd:YAG laser settings has been discouraged in view of dreaded complications. Patterned SCAn Laser(PASCAL) offers decreased energy delivery to retinal tissue and thereby lesser complications. We sought to compare safety profile of SSPRP using PASCAL with multiple-session(MS) conventional laser.

Methods: We randomised consecutive 31 eyes of persons with PDR with high-risk characteristics (HRC) recommended PRP as per ETDRS criteria to SSPRP using PASCAL(n=15) and MSPRP using conventional laser(n=16). In this controlled clinical trial comprising follow up at 6, 12 and 24 weeks, retreatment with conventional laser would be provided in case of non-regression or aggravation of neovascularisation at 12 weeks. Main outcome measures comprised fluence, pain using visual analogue scale, session duration, best corrected visual acuity (logMAR), +90D slit lamp bio-microscopy, indirect ophthalmoscopy, fundus fluorescein angiography, optical coherence tomography, intra-ocular pressure, slit-lamp assisted gonioscopy, Humphrey visual field (HVF) SITA standard 30-2 analysis.

Results: Fluence, pain and session duration were found to be lower for PASCAL in both the groups (p=0.001). HVF was less affected in case of PASCAL at 12 and 24 weeks, rest parameters being equivalent. There was no evidence of narrowing of anterior chamber angle, intraocular pressure elevation or choroidal or retinal detachment in either of the groups.

Conclusion: PASCAL appears to be at an advantage with respect to fluence, pain, session duration and HVF analysis, besides allowing safe single sitting PRP. Both laser delivery systems are equally efficacious with relatively lower side-effects for PASCAL.