Comparison of Biometric Measurements Between IOL Master 700 and MS-39 in Post-LASIK Myopic Eyes: Implications for IOL...

BACKGROUND: Accurate ocular biometry is essential for achieving optimal refractive outcomes in cataract surgery. In patients with prior myopic LASIK, however, biometric calculations remain particularly challenging due to altered corneal anatomy.

PURPOSE: This study aims to compare preoperative biometric measurements obtained from the Zeiss IOL Master 700 and the CSO Ray-Tracing MS-39 in patients with a history of myopic LASIK. The goal is to assess the consistency and clinical relevance of these measurements to support intraocular lens (IOL) power selection in this complex patient group.

SETTING: Longitudinal, monocentric, retrospective study, conducted at the Ophthalmology Department of the University Hospital of Modena.

METHODS: Patients over 18 years of age scheduled for cataract surgery with a history of myopic LASIK and available preoperative biometry from both the IOL Master 700 and MS-39 were included. Exclusion criteria were incomplete clinical records, prior intraocular surgery, or significant ocular pathologies affecting measurement accuracy. The primary outcomes were differences in calculated emmetropic IOL power and predicted postoperative refraction. Secondary outcomes included comparisons of anterior chamber depth (ACD), central corneal thickness (CCT), average keratometry (K-avg), total corneal power (total keratometry [TK] from IOL Master 700 vs. mean pupil power [MMP] from MS-39), and predicted post-operative spherical equivalent (SE) by using the same IOL power, calculated from the IOL Master 700.

RESULTS: Seventy-six eyes from 41 patients (mean age 46.54 ± 12.70 years; 60.98% female) were analysed. The average axial length was 25.93 ± 1.55 mm. An IOL constant of 119.0 was used uniformly across both devices. Statistically significant differences were found in all biometric parameters: ACD (p = 0.00 001), CCT (p = 0.0189), K-avg (p = 0.00 009), and total keratometry (p = 0.00 001). However, no significant differences were observed in the selected IOL power for emmetropia (p = 0.72 527), the predicted postoperative SE of the IOL Master 700 vs. the MS-39 (p = 0.81 642), or the predicted postoperative SE by using the same IOL power, calculated from the IOL Master 700, (p = 0.38 938).

CONCLUSIONS: Despite statistically significant differences in individual biometric parameters between the IOL Master 700 and MS-39, these did not impact final IOL power selection or predicted refraction in post-myopic LASIK patients. Utilizing multiple biometry devices may still enhance confidence and accuracy in surgical planning for this complex group of patients.