Background: To determine the correlation between the area of morphological changes on the macular surface, the depth of intraretinal changes and the best-corrected visual acuity (BCVA) in patients with idiopathic epiretinal membrane.
Methods: In this prospective cross-sectional study, 38 patients underwent BCVA testing with a Snellen eye chart. The depth of traction, photoreceptor outer segment layer (PROS) thickness, central macular thickness (CMT) and presence of intraretinal cysts were measured using the Avanti RTVue XR and 3D Widefield Enface OCT instruments. Enface sections were performed at the inner limiting membrane (ILM) line level (ILM offset). Patients were categorized into two groups: in group 1 (n = 21), the depth of traction was within 90 μm from the ILM, and in group 2 (n = 17) it was beyond 90 μm from the ILM. The main outcome measure was the correlation between area of epiretinal traction and BCVA according to the depth of traction.
Results: In group 1, the depth of traction was 55.15 ± 14.28 μm, the area of traction was 38.95 ± 13.63 mm2, PROS thickness was 51.20 ± 7.23 μm, and CMT was 362.65 ± 41.08 μm. In group 2, the depth of traction was 112.24 ± 10.89 μm, the area of traction was 25.18 ± 4.07 mm2, PROS thickness was 50.24 ± 9.01 μm, and mean CMT was 534.29 ± 126.81 μm. Statistically significant differences in depth of traction, area of traction and CMT were found between the two groups (P < 0.001). The relationship between structure and function between the area of traction and BCVA was better explained in group 2 (r = 0.814, P < 0.001).
Conclusions: We found that intraretinal changes were induced by the ERM, and varied according to the depth of traction measured with en face analysis. In the case of traction deeper than 90 μm, we found a significant correlation between the inner area of the epiretinal traction and BCVA. We believe that retinal stress induced by epiretinal traction is better characterized by combining information provided by sagittal and transverse OCT scans, thus defining its prognostic significance in ERM.
Keywords: En face OCT; Epiretinal membrane; Intraretinal cysts; Tangential traction.