Phacoemulsification is one of the best surgical treatments for the cataract. According to the technical advances to estimate the Interaocular lens (IOL) power, the refractive errors, one of the most important surgical complications after surgery, are now reduced. Currently two methods of biometry to calculate the IOL power is used: ultrasound biometry and optical biometry. Both methods have their own advantage and it is controversial to use which of them before surgery. We aimed to determine the possible differences between these two biometry methods to reduce refractive errors after cataract surgery. Background: This cohort study was conducted on the patients who underwent Phacoemulsification due to cataract in two educational hospitals and one private clinic of ophthalmology. We compared eye refractions after cataract surgery in patients underwent ultrasound or optical biometry. Methods: Eye refraction of 132 patients was studied (n=76 in group one and n=56 in group two).The mean absolute refractive error (MARE) was determined for both groups. The MARE was 0.67±0.70 diopters for the first group and 0.79±0.76 diopters for the second one, without significant statistical difference. Findings: According to our findings and the non-significant difference in the refractive errors after Phacoemulsification in ultrasound and optical biometry methods, both biometry methods could be used for patients; however as optical biometry is more user- and patient-friendly, it may be used more frequently. More researches are warranted to determine the priorities of these methods. Conclusion: Cataract, ultrasonography, refractive error Key words