The Incidence of Posterior Ocular Astigmatism in a Refractive Surgery Population as Determined by the Direct Reduction of Topography Measured Astigmatism.

Purpose: A retrospective study to determine the incidence of posterior ocular astigmatism (POA) after removal of topography guided excimer laser ablation utilizing topography measured astigmatism and axis to remove anterior corneal astigmatism and measure residual astigmatism in 1500 eyes. Methods: WaveLight Contoura was performed with topography measured astigmatism and axis, and all inaccurate outcomes were analyzed for the presence of low topographic astigmatism and significant residual manifest astigmatism. A secondary enhancement procedure was then performed, and measurements taken to measure the presence of topography measured astigmatism and the lack of manifest astigmatism to confirm that POA had been present. Results: Out of the 1500 eyes, 44 were confirmed to have POA, resulting in an incidence of 2.93%. The average amount of manifest astigmatism in these eyes post-primary procedure was 1.13D, and the average topography measured astigmatism was 0.39D. After secondary enhancement with wavefront optimized ablation, the average amount of post-operative astigmatism was 0.01D, and the average amount of topography measured astigmatism was 1.11D. Post-secondary enhancement procedure, average higher-order aberration was reduced 9%. Conclusion: The incidence of 2.93% is lower than prior estimated amounts of posterior ocular astigmatism.