Laser Treatment of Diabetic Macular Edema: Comparison of ETDRS-Level Treatment with Threshold-Level Treatment by Using High-Contrast Discriminant Central Visual Field Testing

Abstract

Grid laser is recognized as an extremely effective treatment of diabetic macular edema, although it causes significant chorioretinal damage when applied and scars that expand with time. The purpose of this study is to compare the effects of two methods of grid laser photocoagulation for diabetic macular edema on high-contrast target discrimination in the central visual field. Grid laser photocoagulation with the Early Treatment Diabetic Retinopathy Study intensity burns has previously been shown to cause full retinal thickness burns. In this study, it produced severe destruction of paraxial vision, most marked at 2 degrees to 10 degrees from fixation. Grid laser using threshold-level burns, in contrast, appeared to produce some improvement in thresholded high-contrast vision at eccentricities from 2 degrees to 3 degrees outward, but failed to normalize visual parameters at these intercepts or at intercepts closer to fixation. Therefore, the recommendations are made (1) to use screening modalities other than biomicroscopic perception of retinal swelling to define earlier opportunities for intervention in the diabetic maculopathic process and (2) to use threshold or sub-threshold methods of laser grid photocoagulation for treating leakage and/or edema.

Restoration of Retinal Structure and Function after Selective Photocoagulation

“…Focal and grid laser photocoagulation is an effective treatment of macular edema, but also causes scotomata and scarring (Morgan and Schatz, 1989;Schatz et al, 1991;Early Treatment Diabetic Retinopathy Study Research Group, 1995). Laser burns can enlarge postoperatively and cause choroidal neovascularization (Lewen, 1988;Lewis et al, 1990), subretinal fibrosis (Guyer et al, 1992;Rutledge et al, 1993;Lövestam-Adrian and Agardh, 2000), and additional visual field loss (Striph et al, 1988;Hudson et al, 1998;Ishiko et al, 1998;Mainster, 1999;Sinclair et al, 1999). Over time, loss of one class of retinal cells may, by trans-synaptic degeneration and associated inflammation, result in the loss of other retinal neurons (Stone, 1950;Birnbach et al, 1994) and RPE remodeling (Framme et al, 2009) or retinal remodeling (Marc et al, 2007).…”

Intravitreal triamcinolone acetonide combined with subthreshold grid laser treatment for macular oedema in branch retinal vein occlusion: a pilot study

“…The Branch Vein Occlusion Study Group demonstrated that grid laser photocoagulation is effective in reducing the visual acuity loss due to MO secondary to BRVO 2. Unfortunately, conventional grid laser treatment leads to a very limited improvement of visual acuity,2 and may be associated with the occurrence of several complications, including enlargement of laser scar,3 – 5 choroidal neovascularisation,6 7 subretinal fibrosis,8 – 11 and visual-field sensitivity deterioration 12 – 17…”

Relationships between clinical measures of visual function and anatomic changes associated with bevacizumab treatment for choroidal neovascularization in age-related macular degeneration

“…13 The device was developed to improve the measurement of visual performance in eyes with macular disease under luminance, hue, and contrast conditions that simulate conditions encountered in normal tasks of daily living.…”