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10 - 14 Sept. 2016, Bella Center, Copenhagen, Denmark

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Comparison of calculated astigmatism and predicted outcomes of various toric intraocular lens calculators

Poster Details

First Author: S. Kochar INDIA

Co Author(s):    S. Das   M. Kurian   S. Madhu              

Abstract Details


To compare the cylindrical power of toric Intraocular lens obtained using the Tecnis toric calculator (Abbott Medical Optics), Barrett online calculator and Baylor’s nomogram and to evaluate the predicted residual cylinder using Tecnis toric calculator and Barrett online calculator.


Tertiary eye care centre, Bangalore, India


Seventy-three eyes of fifty-eight patients who underwent cataract surgery with toric intraocular lens(IOL) implantation were included. Thirty-four eyes had with-the-rule astigmatism(WTR) and thirty-nine eyes had against-the-rule astigmatism(ATR). Cylindrical power of the Intraocular lens was calculated using Tecnis calculator, Barrett calculator and Baylor’s nomogram for both ATR and WTR astigmatism groups. The achieved residual cylindrical power was measured at six weeks after surgery. Pearson’s co-relation co-efficient (R2) was used to compare predicted residual cylinder with achieved residual cylinder using both Tecnis and Barrett calculator. R2 value of 1 indicates 100% co-relation and a perfect outcome.


For WTR astigmatism both Barrett calculator and Baylor’s nomogram gave an under-correction compared to Tecnis calculator. Mean prediction error of residual cylinder was 0.89±0.68 and 0.94±0.93 using the Barrett’s and Tecnis formula respectively for WTR and 0.9±0.6 and 0.78±0.68 respectively for ATR astigmatism. When predicted residual cylinder and the achieved residual cylinder was plotted, the slope of the trend line shows R2 of 0.0025 and 0.075 for Tecnis and Barrett respectively in WTR and R2 of 0.0256 and 0.0753 in ATR astigmatism. The range of residual cylinder for Barrett was less compared to Tecnis calculator.


Both Barrett calculator and Baylor nomogram gave comparable IOL cylinder power and they both consider age related shift to ATR astigmatism. Barrett calculator is more user friendly. Barrett calculator is more accurate than Tecnis calculator in terms of residual cylinder prediction.

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