Aim: The aim of the study is to demonstrate the accuracy of the application of the third generation formula SRK/T in achieving target refraction, i.e. emetropic postoperative refraction in 30 patients who have undergone ultrasound phacoemulsification cataract surgery. Study type: Prospective cohort study. Patients and Methods: The study included 30 successively enrolled patients who underwent ultrasound phacoemulsification cataract surgery, performed by the same surgeon at the Institute of Ophthalmology, University Hospital Centre Osijek, from March to May 2017. The exclusion criteria were irregular astigmatism, corneal transplantation, previous refractive surgery, corneal disease and keratoconus. All patients underwent preoperative keratometry, intraocular lens power calculation prior to surgery using SRK/T ultrasound biometry, visual acuity prior to surgery and one month after surgery, residual refraction after autorefractometer surgery and best corrected visual acuity assessment one month after surgery. Results: 19 out of 30 patients needed corrections a month after surgery (63%). 10 patients had spherical corrections (53%), and 9 had cylindrical (47%) corrections. 60% of patients with a spherical correction had a correction higher than - 0.50 dsph. 56% of patients with a cylindrical correction had a correction higher or equal to - 0.75 dcyl. 20% of the total patient sample receives spherical correction higher than -0.50, and 16.66% of the total patient sample receives cylindrical correction higher than -0.50 dsph. Conclusion: The SRK/T formula proved to be accurate in the IOL calculation that was embedded in the subjects after the cataract extraction by ultrasound phacoemulsification. The best corrected visual acuity of all patients improved after ultrasound phacoemulsification cataract surgery.