Foveal contour as a significant predictor of surgical outcome in idiopathic epiretinal membrane

Abstract

Objective To observe the foveal contour characteristic of idiopathic epiretinal membrane (iERM). Methods A total of 53 eyes in 52 patients with iERM who underwent pars plana vitrectomy with epiretinal membrane and inner limiting membrane peeling were enrolled in this retrospective study. All eyes received the examination of optical coherence tomography (OCT) and minimum resolution angle in logarithmic (logMAR) best corrected visual acuity (BCVA). Foveal contour grading was according to the ratio of central macular thickness (CMT) to the thickness of the retina 1 mm away on OCT line scan: Grade 0, depressed; Grade 1, flat; Grade 2, elevated. Baseline foveal contour grade was as follows: 28 eyes with Grade 1 (Group 1), and 25 eyes with Grade 2 (Group 2). The mean logMAR BCVA was 0.40±0.26 in Group 1, and 0.60±0.27 in Group 2 respectively. The mean CMT was (433.52±133.05) μm and (571.70±85.40) μm respectively. The logMAR BCVA and CMT both demonstrated significant difference between the two groups (t=-2.825, -4.512; P<0.05). OCT images and BCVA at 1, 3 months after surgery were collected and analyzed. The change in foveal contour, BCVA and CMT were evaluated. The relationship between surgical outcome and different preoperative grading was analyzed. Results Foveal contour grade at 3 months after surgery was as follows: 15 eyes with Grade 0, 21 eyes with Grade 1, and 17 eyes with Grade 2, demonstrating significant difference compared with baseline (Z=-3.588, P<0.05). In Group 1, there were 12 eyes with Grade 0, 10 eyes with Grade 1, and 6 eyes with Grade 2 postoperatively. In Group 2, there were 3 eyes with Grade 0, 11 eyes with Grade 1, and 11 eyes with Grade 2 postoperatively. The postoperative foveal contour grade was significantly different between the two groups (Z=-2.466, P<0.05). The logMAR BCVA at 1, 3 months after surgery both improved significantly compared with baseline (P<0.05) in Group 1 (t=-3.226, -5.439) and Group 2 (t=-4.137, -5.919). The logMAR BCVA at 1, 3 months after surgery demonstrated significant difference between the two groups (t=-2.231, -2.291; P<0.05). The CMT decreased significantly at 1, 3 months after surgery in Group 1 (t=-2.674, -4.090) and Group 2 (t=-9.663, -9.865) compared with baseline (P<0.05). The CMT at 1, 3 months after surgery demonstrated significant difference between the two groups (t=-2.825, -3.003; P<0.05). The improvement of logMAR BCVA 3 months after surgery was negatively correlated (P<0.05) with preoperative logMAR BCVA (r=-0.758) and preoperative CMT (r=-0.359). Conclusion In iERM eyes, flat foveal contour had better surgical prognosis than elevated ones. Key words: Macula lutea; Membranes; Vitreoretinal surgery; Tomography, optical coherence