Abstract
Purpose: :
To correlate the ratios of inner and outer retinal layer thickening (measured by spectral-domain optical coherence tomography) with visual acuity (VA) in idiopathic epiretinal membrane (ERM) patients.
Methods: :
We examined 30 eyes of 25 patients reffered to Kyoto University Hospital from May to November, 2007 using RTVue-100 (Optovue). Further, 25 eyes of 25 healthy volunteers were examined as normal controls. The inner, outer, and full retinal thickness at the fovea (within a circle of diameter of 1mm), parafovea (within a ring of diameters 1 and 3mm) and perifovea (within a ring of diameters 3 and 5mm) were measured using a scan protocol of MM5. The inner retinal thickness was defined as the distance between the vitreoretinal interface and the outer border of the inner plexiform layer. Correlation between the % thickening ratio (thickness in each eye with ERM - mean normal thickness/mean normal thickness) and logarithm of the minimal angle of resolution (LogMAR) visual acuity was analyzed using Pearson correlation.
Results: :
The mean ages in ERM and control groups were 69.6 ± 6.8 (58-81 years) and 67.4 ± 6.4 (53-77 years), respectively; mean LogMAR VA was 0.12 ± 0.21 (-0.079 to 0.824) and -0.11 ± 0.07 (-0.176 to 0), respectively. The full retina showed 71% thickening in the fovea, 26% in the parafovea, and 14% in the perifovea. The inner retina showed 101% thickening in the fovea, 22% in the parafovea, and 13% in the perifovea. The outer retina showed 59% thickening in the fovea, 29% in the parafovea, and 15% in the perifovea. The full retinal thickness in the fovea (r = 0.561, P = 0.001) and parafovea (r = 0.469, P = 0.009) were significantly correlated with the LogMAR VA, but that in the perifovea (r = 0.264, P = 0.159) was not. The thickness of outer retinal layer in the fovea (r = 0.644, P < 0.001), parafovea (r = 0.616, P < 0.001) and perifovea (r = 0.410, P = 0.025) were significantly correlated with the LogMAR VA, whereas inner retinal thickness was not (fovea, r = 0.279, P = 0.135; parafovea, r = -0.048, P = 0.802; perifovea, r = -0.024, P = 0.899).
Conclusions: :
The ratio of the outer retinal thickening in the fovea and parafovea correlated well with the VA. In contrast, the ratio of the inner retinal thickening was not correlated to VA, although this ratio was much more than that of the outer retina in the fovea. This suggests that ERM-induced retinal damages attributing to decrease of VA are located within the outer retina exterior to the inner plexiform layer.
Keywords: imaging/image analysis: clinical • macula/fovea • visual acuity