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Neal Kansara, Zachary Landis, Catherine Seeger, Andrew Luo, Jack Quillen, Tara O'Rourke, Brett Ernst, Ingrid U Scott, Seth Pantanelli; Nittany Nomogram: A Method to Predict Refractive Astigmatism after Cataract Surgery Based on Pre-operative Biometry. Invest. Ophthalmol. Vis. Sci. 2020;61(7):1678.
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© ARVO (1962-2015); The Authors (2016-present)
To develop a method of predicting refractive astigmatism (RA) after cataract surgery using pre-operative biometry data.
A training database was assembled between November 2014 and June 2018, which included consecutively operated eyes that underwent pre-operative optical biometry (IOLMaster), cataract surgery with placement of a monofocal intraocular lens by, or supervised by, a single surgeon, and post-operative manifest refraction greater than 1 month after surgery. Eyes with clinically significant corneal disease, prior refractive surgery, or a post-operative best-corrected visual acuity worse than 20/40 were excluded. A nomogram was developed that predicted RA from pre-operatively obtained biometry. A separate, similar testing database was assembled from a second surgeon and used to assess the performance of the new nomogram and compare it to that of the Barrett Toric Calculator’s net astigmatism prediction. Outcome measures included the difference vector (DV) magnitude (defined as the vector added difference between actual and predicted RA), proportion of eyes with a DV magnitude < 0.5 diopter (D), and proportion of eyes in which the astigmatism class (e.g. against-the-rule [ATR], with-the-rule [WTR], or oblique) was predicted correctly.
The training and testing databases consisted of 230 and 687 eyes, respectively. The mean DVs for all eyes (0.17 D and 0.21 D), ATR anterior corneal astigmatism (ACA) (0.26 and 0.41 D), WTR ACA (0.09 and 0.21 D), and oblique ACA (0.16 and 0.02 D) were similar for the Nittany Nomogram (v2.06) and Barrett Toric Calculator. The proportion of eyes that had a DV magnitude < 0.5 D were 51.7 and 51.3% for the Nittany Nomogram and Barrett Toric Calculator, respectively. The proportion of eyes for which the two nomograms predicted the astigmatism class correctly was 62.5% and 65.7%, respectively.
The newly developed Nittany Nomogram performs similarly to the Barrett Toric Calculator with respect to predicting net astigmatism based on pre-operative biometry values. Further validation is needed, especially on eyes with oblique and higher magnitudes of corneal astigmatism.
This is a 2020 ARVO Annual Meeting abstract.
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