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Eugene Alan Lowry, Sundeep Kasi, Ayman Naseri, Seth Blumberg, Priya Morjaria, Steven C Schallhorn; The Effect of Corneal Astigmatism Orientation on Toric Intraocular Lens Outcome. Invest. Ophthalmol. Vis. Sci. 2016;57(12):1318.
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© 2017 Association for Research in Vision and Ophthalmology.
Pre-operative corneal topography measures the anterior corneal surface, though most patients have some posterior corneal astigmatism that may differentially affect outcomes in with versus against the rule astigmatism. We investigate differences in astigmatic correction in cases of with the rule (WTR), against the rule (ATR) and oblique astigmatism.
Retrospective analysis on all patients undergoing cataract surgery with implantation of an M Plus Toric Lens with a single corporation in the United Kingdom. Automated keratometry, uncorrected and best-corrected visual acuity, and manifest refraction was obtained pre-operatively as well as at months 1 and 3 post-operatively. Data were stratified by type of pre-operative corneal astigmatism (WTR, ATR, oblique). Analysis was performed in accordance with American National Standards Institute (ANSI) guidelines on astigmatic corrections and included a non-vector safety and stability analysis as well as vector analyses. Continuous variables were compared with Kruskal-Wallis testing and dichotomous with Fisher exact testing.
1076 eyes of 714 patients undergoing cataract surgery with a toric lens were included. There was no evidence of baseline difference in magnitude of cylindrical error between groups (p = 0.50). Fewer patients with oblique astigmatism obtained uncorrected visual acuity of at least 20/40 compared against WTR and ATR astigmatism (84%, 94% and 96%, respectively, p = 0.01). Patients who had WTR astigmatism compared with oblique and ATR, respectively, had higher vector magnitudes of surgically induced refractive correction (3.07D, 2.59D, 2.57D; p< 0.001) and larger correction ratios, defined as the ratio of magnitudes of surgically induced correction divided by intended correction vectors (1.17, 1.03, 0.96; p <0.001).
Cataract surgery using toric intraocular lenses tends to overcorrect patients having with the rule astigmatism and slightly under correct against the rule astigmatism, consistent with the fact that posterior corneal astigmatism is generally steeper in the vertical meridian.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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