Predictions of Residual Astigmatism from Surgical Planning for Topographic-Guided LASIK Based on Anterior Corneal Astigmatism (LYRA Protocol) vs the Phorcides Analytic Engine

PURPOSE: To identify the laser programming strategy that achieves the highest refractive astigmatism outcomes accuracy between LYRA surgical planning and Phorcides surgical planning. METHODS: One hundred one eyes successfully treated with Contoura with LYRA Protocol were retrospectively surgically planned with Phorcides to determine its accuracy. Eighteen eyes that had inaccurate 3 month outcomes with LYRA were also retrospectively planned with Phorcides. Two patients with one eye treated with LYRA and one with Phorcides surgical planning were analyzed for outcomes. RESULTS: Retrospective Phorcides surgical planning deviated from already successful treatments with LYRA Protocol 51% of the time, with an average astigmatic deviation of 0.69 diopters (D) and an average deviation of 7.1 degrees. The percentage of eyes of the 101 successfully treated with LYRA Protocol then planned with Phorcides differed by 0.5D in 19.8%, by 0.75D in 23.8%, and by 1D in 7.9%. A retrospective analysis with Phorcides of patients treated with LYRA Protocol with residual post-operative astigmatism demonstrated that Phorcides would have increased accuracy in only 33% of patients, and not helped or decreased accuracy in the rest. CONCLUSION: Phorcides was significantly less accurate in surgical planning than the LYRA Protocol overall and a 51% of primary patients could have a likelihood of significant residual astigmatism. Phorcides would also have provided a less accurate outcome in the majority of patients that needed secondary enhancement.