Tangential Retinal Displacement Increases After Macular Pucker Surgery: An Apparent Nonsense

Purpose: To measure the tangential retinal displacement and vision before and after macular pucker surgery and study if Pars Plana Vitrectomy (PPV) with EpiRetinal Membrane (ERM) peeling allows the reconstitution of previous anatomy or else it results in a different configuration. Methods: Retrospective series of patients undergoing PPV for ERM, with greater than 6-month follow-up before and after surgery, complete with best-corrected visual acuity (BCVA), Optical Coherence Tomography (OCT), M-charts, and InfraRed (IR) retinography. Tangential retinal displacement between Earliest visit (TE), time of surgery (T0) and latest available visit (TL) of the examined retina, concentric circles at 0.5, 1.5 and 4.5mm radii and the central horizontal and vertical meridian were measured. Tangential displacement was calculated as the optical flow of consecutive IR photos. Results: The study comprised 32 patients: 15 males and 17 females. Average pre- and post-operative follow-up were 23.4±27.9 months and 19.2±11.8 months. BCVA reduced before surgery (0.69 ± 0.16 Snellen to 0.46 ± 0.17; p<0.001) and increased after (0.866 ± 0.16 Snellen; p<0.001). Horizontal and vertical metamorphopsia increased between before surgery but only horizontal metamorphopsia significantly reduced after. Average tangential displacement before surgery was 35.6±29.9 µm versus 56.6±41.3 µm after (p=0.023). Pre- and post-operative displacement within the fovea was less than over the entire area (p<0.001). Conclusion: Retinal tangential displacement between diagnosis and surgery (TE-T0) is less than the displacement occurring after surgery (T0-TL). Post-operative displacement does not represent the restoration of the anatomy existing before the disease ensued, but rather the resulting equilibrium of newly deployed forces.