Vector analysis of astigmatic changes after cataract surgery with toric intraocular lens implantation

PURPOSE: To analyze the astigmatic changes after cataract surgery with toric intraocular lens (IOL) implantation and determine the relationship between these changes and the final visual outcomes. SETTING: Vissum-Instituto de Oftalmologico de Alicante, Alicante, Spain. DESIGN: Prospective case series. METHODS: This study comprised eyes with visually significant cataract that had surgery with Acrysof toric IOL implantation. Refractive, corneal topography, internal astigmatism, and contrast sensitivity outcomes were evaluated over 6 months. The Alpins vectorial method was used to analyze the target (TIA) and surgically (SIA) induced astigmatism, difference vector, magnitude of error, flattening effect, and torque. RESULTS: The study enrolled 27 eyes (21 patients). Postoperatively, there was a significant reduction in refractive cylinder (P<.01) with an associated visual improvement (P<.01). The magnitude of the SIA vector was significantly lower than the TIA 1 month and 6 months after surgery (P<.01). The mean magnitude of the difference vector was 0.91 diopter (D) +/- 0.45 (SD) at 6 months, with no significant differences between postoperative visits (p>0.19). The mean magnitude of torque vector was 0.59 +/- 0.42 D at 6 months. There was a significant negative correlation between refractive cylinder and the magnitude of torque (r <= -0.54, P<.01) and the difference vector (r = -0.98, P<.01). CONCLUSION: The toric IOL restored distance visual function in eyes with cataract and significant corneal astigmatism, although there was a small trend toward undercorrection related to misalignment of treatment.