Visual acuity and microperimetric mapping of lesion area in eyes with inflammatory cystoid macular oedema

Purpose: To evaluate the effect of fluid accumulation on local visual function in inflammatory cystoid-macular-edema (ICME). Methods: This cross-sectional study applied optical-coherence-tomography over a 12x12 fovea-centered field in 50 patients with ICME and mapped the extent of fluid-filled spaces in various retinal layers, of subretinal-fluid and of diffuse-edema. Regression analysis examined effect of planimetric fluid-distribution on best-corrected-visual-acuity (BCVA) and mean microperimetric-sensitivity. Results: BCVA decreased with increasing central-neuroretinal-thickness (r=0.52, p=0.001), total central-retinal-thickness, including subneuroretinal-fluid (r= 0.41, p=0.006), total cystoid-and-diffuse edema-area (r=0.35, p=0.036) and cystoid inner-nuclear-layer area (r=0.39, p=0.02). Mean retinal-sensitivity decreased with increasing diffuse edema-area (r=-0.86, p<0.0001), total cystoid-and-diffuse edema-area (r=-0.54, p=0.001), cystoid inner-nuclear-layer area (r=-0.46, p=0.008) and cystoid ganglion-cell-layer area (r=-0.6, p=0.049), central-neuroretinal-thickness (r=-0.42, p=0.028) and total central-retinal-thickness (r=-0.34, p=0.039). In multivariate-analyses BCVA was best described by central-neuroretinal-thickness, duration of edema, total cystoid-and-diffuse edema-area and cystoid inner-nuclear-layer area (R-2=0.5, p= 0.002). Mean retinal-sensitivity was best described by diffuse edema-area, total cystoid-and-diffuse edema-area and central-neuroretinal-thickness (R-2=0.75, p<0.0001). Subretinal-fluid area and cystoid outer-nuclear/Henle's layer area had no effect on either BCVA or microperimetry. Conclusions: Thickening of the neurosensory-fovea, not subfoveal-fluid, had major impact on both BCVA and retinal-sensitivity. The extent of edema in inner retinal layers also had major impact on both of these two functional parameters. Visual-impairment seems to differ depending on the layers involved, thus different types of fluid accumulation may potentially be given varying treatment priorities.