J Korean Ophthalmol Soc.  2020 Nov;61(11):1265-1272. 10.3341/jkos.2020.61.11.1265.

Accuracy of Intraocular Lens Power Calculations Based on Total and Standard Keratometry

Affiliations
  • 1Saevit Eye Hospital, Goyang, Korea

Abstract

Purpose
To compare the accuracy of standard and total keratometry data obtained using the Barrett Universal II and Barrett Toric Calculator.
Methods
In total, 111 eyes of 111 patients who visited our hospital for cataract surgery from February 2019 to September 2019 were included in this study. Total keratometry and standard keratometry data were obtained using the Barrett Universal II and the Barrett Toric Calculator; mean absolute errors were derived by using preoperative IOL Master 700® (Carl Zeiss Meditech AG, Jena, Germany) data and 2-month postoperative manifest refraction data. The mean absolute errors of the two methods were compared in terms of a posterior corneal astigmatism greater than 0.3 diopter (D) in patients fitted with Toric intraocular lenses.
Results
Using the Barrett Universal II formula, the mean absolute error spherical equivalent difference between total keratometry and standard keratometry was 0.021 ± 0.102 D (p = 0.65) when the Barrett Toric Calculator was used. The mean absolute error differences between the two methods were 0.015 ± 0.121 D for the spherical equivalent (p = 0.80) and 0.005 ± 0.870 D for the cylinder measurement (p = 0.94). In terms of a posterior corneal astigmatism greater than 0.3 D, the mean absolute error spherical equivalent and cylinder measurement differences were -0.020 ± 0.107 D (p = 0.70) and -0.023 ± 0.055 D (p = 0.50) in patients fitted with Toric intraocular lenses.
Conclusions
The total keratometry method, which directly measures posterior corneal curvature, yields data comparable to those of the standard keratometry method. When the posterior corneal astigmatism was greater than 0.3 D, we found no significant difference between the total keratometry and standard keratometry data of patients fitted with Toric intraocular lenses.

Keyword

Barrett toric calculator; Barrett Universal II; IOL Master 700®; Posterior corneal astigmatism; Total keratometry
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