The learning curve of murine subretinal injection among clinically trained ophthalmic surgeons

Abstract

ABSTRACTPurposeSubretinal injection (SRI) in mice is widely used in retinal research, yet the learning curve (LC) of this surgically challenging technique is unknown.MethodsTo evaluate the LC for SRI in a murine model, we analyzed training data from 3 clinically trained ophthalmic surgeons from 2018 to 2020. Successful SRI was defined as either the absence of retinal pigment epithelium (RPE) degeneration after phosphate buffer saline injection and the presence of RPE degeneration after Alu RNA injection. Multivariable survival-time regression models were used to evaluate the association between surgeon experience and success rate, with adjustment for injection agents, and to calculate an approximate case number to achieve a 95% success rate. A Cumulative Sum (CUSUM) analysis was performed and plotted individually to monitor each surgeon’s simultaneous performance.ResultsDespite prior microsurgery experience, the combined average success rate of the first 50 cases in mice was only 27%. The predicted SRI success rate did not reach a plateau above 95% until approximately 364 prior cases. Using the 364-training case as a “cutoff” point, the predicted probability of success before and after the 364th case was 65.38% and 99.32%, respectively (P < 0.0001). CUSUM analysis showed an initial upward slope and then remained within the decision intervals with an acceptable success rate set at 95% in the late stage.ConclusionsThis study demonstrates the complexity and substantial LC for successful SRI in mice with high confidence. A systematic training system could improve the reliability and reproducibility of SRI-related experiments and improve the interpretation of experimental results using this technique.Translational RelevanceOur prediction model and monitor system allow objective quantification of technical proficiency in the field of subretinal drug delivery and gene therapy for the first time.