Accuracy of the SRK/T Formula Using Partial Coherence Interferometer, Al-Scan after Phacoemulsification

Abstract

To evaluate the accuracy of SRK/T formula used for IOL power calculation by partial coherence interferometer in patients undergoing phacoemulsification surgery. Patients and methods: A prospective interventional clinical study included 40 eyes of 34 patients who underwent uncomplicated phacoemulsification with IOL implantation from March 2015 to March 2017. Biometries were measured using ultrasound or AL-scan and intraocular lens power was calculated using the SRK-T formula. Patients were divided into 2 groups based on device used for IOL power calculation: ALscan or ultrasound ; Axial length: >=25 mm or < 25mm; or lens opacity: Cataractous or clear lens. The mean error (ME) was calculated from the difference between the formula predicted refractive error and the actual post operative refractive error by the end of the followup (3 months postoperative). Results: Mean axial length measured preoperatively was 27.47 ± 316mm (21.55-34.05) mm. 60 percent of the patients were within 0.5 D of the predicted refractive error and 90 percent were within 1.0 D. There was no statistically significant difference in the overall performance of the SRK/T formula between the mean error when dividing the patients into 2 groups according to: device used for IOL power calculation (P= 0.274); Axial length (P= 0.46); or lens opacity (P= 0.18) in precision of predicting postoperative refraction. Conclusions : SRK/T formula helps in improvement of the accuracy of IOL power calculation and decreasing the postoperative refractive error. By using SRK/T formula, there was no statistically significant difference between the AL-scan or applanation ultrasound used in biometry.