Lack of stereopsis does not reduce surgical performance but prolongs the learning curve of vitreoretinal surgery

Purpose: To investigate whether individuals with long-term reduced stereopsis were able to obtain the same level of surgical skills in simulated vitreoretinal surgery on the Eyesi Surgical Simulator as individuals with normal stereopsis. Methods: Twenty-four medical students were recruited and divided into two groups according to their degree of stereopsis: Group 1 (n = 12) included subjects with normal stereopsis (60 arcsec or lower) and Group 2 (n = 12) included subjects with reduced stereopsis (120 arcsec or higher). Stereopsis was tested using the TNO test (Lameris Ootech BV, Nieuwegein, the Netherlands). The participants were trained in virtual reality-simulated vitreoretinal surgery and continuously measured using a test with solid validity evidence and a pre-defined pass–fail score. All data were analysed using the Wilcoxon rank sum test. Results: We observed no differences in overall performance scores for any of the four modules. The participants with reduced stereopsis used 5.8 more attempts in bimanual training (p = 0.04), 8.8 more attempts in removal of posterior hyaloid (p = 0.04), 9.1 more attempts in navigation training (p = 0.20) and 0.3 fewer attempts in removal of internal limiting membrane (p = 0.69). Conclusion: The final performance scores on the Eyesi Surgical Simulator were independent of the degree of stereopsis. However, the number of attempts to achieve the pre-defined pass–fail score increased significantly with reduced stereopsis in two of four modules. These results indicate that a high degree of stereopsis is not necessary to become proficient in microsurgery but may prolong the learning curve.