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Neal Kansara, Tara O'Rourke, Erik Lehman, Ingrid U Scott, Seth Pantanelli; Astigmatism Correction Accuracy with the Barrett and Nittany Toric Calculators. Invest. Ophthalmol. Vis. Sci. 2021;62(8):2896.
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© ARVO (1962-2015); The Authors (2016-present)
To compare the accuracy of residual refractive astigmatism (RA) predictions from the novel Nittany Toric Calculator v0.212 (NTC) to those of the Barrett Toric Calculator (BTC) in eyes implanted with a toric intraocular lens (IOL).
A nomogram was developed that used pre-operative biometry to predict post-operative RA in eyes implanted with a monofocal IOL. This nomogram was combined with the known effective toricities for Alcon Acrysof toric IOLs to create the NTC, which has as inputs pre-operative biometry and outputs residual RA for a given toric IOL implanted at a suggested axis. A separate testing database was assembled, which consisted of consecutive eyes that had toric IOLs implanted between 02/2016 and 02/2019, as recommended by the BTC. The residual RA predictions from the BTC were compared to those from the NTC for the implanted lens. A “remove and replace” method was used to account for differences between the recommended implantation axes of the toric IOL for the BTC and NTC. Outcome measures included the difference vector (DV) magnitude (defined as the vector difference between actual and predicted RA) and proportion of eyes with a DV magnitude <0.5 or <1.0 diopter (D).
The testing database included 82 eyes. The centroid of the DV for all eyes was 0.06 ± 0.50 D x 177 for the BTC and 0.12 ± 0.65 D x 016 for the NTC (p = 0.49). Sub-group analysis revealed centroids of 0.02 ± 0.55 D x 008 and 0.23 ± 0.70 D x 011 in eyes with against-the-rule astigmatism (p = 0.04), 0.15 ± 0.42 D x 177 and 0.06 ± 0.55 D x 066 in eyes with with-the-rule astigmatism (p = 0.06), and 0.07 ± 0.43 D x 104 and 0.04 ± 0.64 D x 062 in eyes with oblique astigmatism (p = 0.95) for the BTC and NTC calculators, respectively. The proportion of eyes that had a DV magnitude <0.5D were 73.2% and 69.5% (p = 0.513), while 93.9% and 92.7% had a DV magnitude <1.0 D, respectively (p = 1.000).
The current iteration of the NTC performs similar to BTC with respect to most outcome measures. Further refinements of the NTC to incorporate the impact of effective lens position may lead to improvements in prediction accuracy.
This is a 2021 ARVO Annual Meeting abstract.
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