Structural and functional implications of severe foveal dystopia in epiretinal membranes.

Purpose: The purpose of this study was to examine the functional and structural correlates of severe foveal dystopia in patients with epiretinal membranes.
Methods: For this retrospective study of 29 eyes with epiretinal membrane, we identified 7 eyes that had severe foveal dystopia (defined as fovea located >200 μm from its expected location) and followed the direction and rate of foveal movement pre- and postoperatively.
Results: Epiretinal membrane traction caused the fovea to move preoperatively at a rate of 275 μm/month from its anatomical location in 2 patients. The final preoperative foveal location was, on average, 1,217 ± 683 μm away from its expected location. Postoperatively, foveal movement toward its expected location was largest during the first month after surgery (mean = 547 ± 340 μm) and slowed down until the final follow-up position was achieved (mean = 301 ± 131 μm). Overall, the fovea moved a total of 848 ± 445 μm, allowing the fovea to correct only 32.8 ± 22.1% of the total displacement from its expected location. A univariate regression model confirmed a linear relationship between preoperative visual acuity and preoperative foveal distance from its expected anatomical location with an R of 0.759 (P = 0.0107).
Conclusion: The extent of tractional foveal dystopia correlates with decreased visual acuity. Although all patients experienced functional and anatomical improvements with surgery, long-standing or severe foveal dystopia may be associated with permanent structural changes that limit functional outcome. Cases with extreme degrees of foveal dystopia may benefit from early intervention to prevent irreversible structural and functional changes.