Comparison of SRK/T and Haigis formulae in the prediction of refractive outcome after phacoemulsification

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Abstract

Purpose
To compare the accuracy of SRK/T and Haigis formulae used for intraocular lens (IOL) power calculation by a partial coherence interferometer in patients undergoing phacoemulsification surgery.
Patients and methods
A prospective interventional clinical study included 70 eyes of 60 patients, who underwent uncomplicated phacoemulsification with IOL implantation from October 2015 to December 2017. Preoperative axial length (AL), corneal curvature (keratometry), and preoperative anterior chamber depth (preoperative ACD) were measured using Nidek AL-scan optical biometer and the IOL power was determined using both SRK/T and Haigis formulae. The difference between the predicted value and the postoperative spherical equivalent was calculated for both the formulae by the end of the follow-up (3 months postoperatively).
Results
The mean errors of the two formulae were SRK/T: −0.225±0.61 D and Haigis: 0.171±0.68 D; the mean absolute errors of the two formulae were 0.534±0.36 and 0.533±0.44 D, respectively. There was no statistically significant difference between the mean error of the two formulas used in the overall performance, but was significant in eyes with an AL of more than 25 mm. The proportion of patients having a prediction error within ±0.50 D of SRK/T formula (54.29%) was comparable to those of Haigis (55.71%) and the prediction errors within ±1.0 D were 87.14 and 85.71%, respectively. There is a weak correlation between the mean AL, keratometry and the Haigis–SRK/T prediction differences (=0.273).
Conclusion
The calculation of IOL power using SRK/T and Haigis formulae resulted in an accurate postoperative refraction. In long AL subcategory, the mean absolute error of Haigis was less compared with the SRK/T formula.

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