Biometry and Intraocular Lens Power Calculation by Combined Scheimpflug-Placido Disc versus Optical Interferometry Devices


Purpose: To compare the results of the current gold standard, laser interferometry, and keratometry by the IOL-Master, with a newly developed Galilei G6 using raytracing software Okulix for intraocular lens (IOL) power calculations.

Methods: For comparison of the IOL-power calculation of both devices, we analyzed the difference between the actual one-month postoperative subjective refraction and the theoretically calculated target refraction before cataract surgery. The IOL was selected according to the IOL Master recommendation aiming for emmetropia after surgery. We analyzed the differences of the measurements of the basic biometric data in 205 healthy eyes by each device.

Results: Our study included 205 healthy, unoperated eyes from 117 patients (61 women, 56 men) aged 20 to 75 years. Twenty-two eyes of cataract patients were also included in this retrospective study design. The mean difference between the prediction of the postoperative refraction and the refraction actually achieved was 0.03 D for the IOL Master and –0.23 D for the Galilei G6. The difference was not statistically significant (P = 0.059). The difference between the IOL power calculation of the IOL Master and the calculation of the G6 was not statistically significant (P = 0.064). The difference between the predicted refraction of the G6 and the refraction achieved after one month was also not statistically significant (P = 0.12) and neither was the difference between the predicted refraction of the IOL Master and the achieved refraction (P = 0.39). The mean axial length was calculated as 24.21 ± 0.80 mm using the IOL Master and 24.27 ± 0.82 mm using the Galilei G6 device. The mean value regarding anterior chamber depth (ACD) of the IOL master was 3.46 ± 0.23 mm and for the Galilei was G6 3.51 ± 0.25 mm. When comparing the white to white (WTW) values of the IOL master, it showed mean values of 12.32 ± 0.31 and Galilei showed mean values of G6 12.21 ± 0.28. All of these differences (between Galileo and IOL Master measurements) were statistically significant (P < 0.001).

Conclusion: Both the laser interferometry/keratometry performed by the IOL Master and the interferometry/raytracing biometry strategy performed by the Galilei G6 demonstrated equal results when executing the IOL power calculation before cataract surgery in eyes with no prior ocular surgery.


Cataract Surgery, IOL Calculation, Ray Tracing

1. Dalto RF, Ferreira MA, Queiroz W, Coelho RP, Paula JS, Messias A. Haigis and SRKT formulae accuracy for intentional myopic overcorrection. Int Ophthalmol 2018;38:1459–1463.

2. Ghoreyshi M, Khalilian A, Peyman M, Mohammadinia M, Peyman A. Comparison of OKULIX ray-tracing software with SRK-T and Hoffer-Q formula in intraocular lens power calculation. J Curr Ophthalmol 2018;30:63–67.

3. Jung S, Chin HS, Kim NR, Lee KW, Jung JW. Comparison of repeatability and agreement between swept-source optical biometry and dual-scheimpflug topography. J Ophthalmol 2017;2017:1516395.

4. Lee JW, Park SH, Seong MC, Cho HY, Kang MH. Comparison of ocular biometry and postoperative refraction in cataract patients between Galilei-G6® and IOL Master®. J Korean Ophthalmol Soc 2015;56:515.

5. Micieli JA, Arshinoff SA. Cataract surgery. CMAJ 2011;183:1621.

6. Ventura BV, Ventura MC, Wang L, Koch DD, Weikert MP. Comparison of biometry and intraocular lens power calculation performed by a new optical biometry device and a reference biometer. J Cataract Refract Surg 2017;43:74–79.

7. Shajari M, Cremonese C, Petermann K, Singh P, Müller M, Kohnen T. Comparison of axial length, corneal curvature, and anterior chamber depth measurements of 2 recently introduced devices to a known biometer. Am J Ophthalmol 2017;178:58–64.

8. Zhu XJ, He WW, Du Y, Qian DJ, Dai JH, Lu Y. [Intraocular lens power calculation for high myopic eyes with cataract: comparison of three formulas]. Zhonghua Yan Ke Za Zhi 2017;53:260–265.

9. Liu YC, Wilkins M, Kim T, Malyugin B, Mehta JS. Cataracts. Lancet 2017;390:600–612.