Concentric Contraction of Retinal Grid Laser Lesions Following a Pattern Scan Laser Treatment Using the Pascal© Laser System

Abstract

Purpose: : To examine intra-retinal morphologic in vivo changes secondary to a focal or grid macular Pascal© laser treatment in the human retina.

Methods: : Fifteen patients with untreated diabetic macular edema (DME) received a focal (group 1) or grid pattern (group 2) photocoagulation treatment using a semi-automated patterned scanning laser system (PASCAL©, Optimedica). All patients were examined at baseline, day 1, week 1 and monthly until month 3 using spectral domain optical coherence tomography (SD OCT; Spectralis OCT©, Heidelberg Engineering) and infrared (IR) and color photo (CF) fundus imaging.

Results: : At day 1, in both groups there were distinct intra-retinal laser lesions only in the outer layers, i.e. the photo receptor layer (PRL), the outer nuclear layer (ONL) and the outer plexiform layer (OPL). Single focal lesions (group 1) were detectable as delineated alterations of theses layers showing a rather perpendicular intra-retinal course with distinct borders surrounded by edematous tissue. Laser lesions of a grid pattern photocoagulation (group 2) showed alterations of the same layers. However, the outer retinal layers, i.e. the retinal pigment epithelium, the PRL and ONL, seemed to be dislocated into the direction of the center of the grid pattern. This resulted in lesions showing a rather diagonal intra-retinal course. Furthermore, in all patients of group 2, there was a clear decrease in central retinal thickness already at day 1, further proceeding until month 3. Apart from that, the closure of intra-retinal microaneurysms and a continuing scarring reaction of the laser lesions at the level of the PRL could be demonstrated until month 3.

Clinical Trial: : www.clinicaltrials.gov NCT00682240

Keywords: diabetic retinopathy • laser • imaging/image analysis: clinical