Comparison of the biometric measurements obtained using noncontact optical biometers LenStar LS 900 and IOL Master V.5

Introduction
Evaluation of the measurement accuracy using a new optical biometer LenStar LS 900 (Haag Strait) and comparison according to the IOL Master V.5 (Zeiss) device.

Material and methods
In a prospective clinical study biometric measurements along with artificial lens power calculation using the LenStar LS 900 device were performed. A total number of 106 patients qualified for a cataract extraction procedure were included in the study. Measurements along with lens power calculation were repeated using the IOL Master V.5. device. Results were elaborated using Pearson’s correlation and Bland-Altman plot.

Results
Measurements were performed in 204 eyes of 106 patients. Mean values and ranges of biometry results were as follows: 23.46 ± 2.81 mm [20.79-29.80] for IOL Master, and 23.47 ± 2.83 mm [20.79-29.86] for LenStar LS 900. In keratometry for flat meridian (K1) the following data was obtained: mean 43.24 ± 3.22 D [range 38.27-47.94] for IOL Master and 42.44 ± 3.15 D [38.27-47.94] for LenStar LS 900. For steep meridian (K2) the data obtained were 44.14 ± 3.40 D; [39.29-49.13] and 43.27 ± 3.34 D [38.61-48.4] respectively. The obtained calculation results for each eye were as follows: mean 21.23 ± 8.07, [range 3.25-28.99] for Hagis formula, 21.14 ± 6.90; [4.83-27.6] for SRK II, 21.04 ± 7.78; [3.05-28.05] for SRK/T, 21.09 ± 8.13; [2.43-28.61] for Holladay using IOL Master and 21.41 ± 8.23; [2.99-29.15] for Haigis; 21.24 ± 7.00; [4.6--27.71] for SRK II, 21.13 ± 7.90; [2.76-28.18] for SRK/T; 21.09 ± 8.13; [2.16-28.76] for Holladay using LenStar LS 900.

Conclusions
The LenStar LS 900 device enables to perform accurate and repetitive biometric measurements and implant power calculations. Implant calculation results obtained using the LenStar LS 900 device are comparable to those achieved using the IOL Master V.5 device, which has been commonly accepted as standard for over a decade. The use of both devices is limited by significant lens opacification and posterior capsule calcification. In such cases, additional ultrasound biometry should be performed. Keratometry results obtained using both devices should not be used alternatively because of the different measurement methods and different refraction indexes. The LenStar LS 900 device comparing to the IOL Master additionally enables pachymetry, macular retinal thickness, lens thickens and pupil diameter measurement. Accuracy of those measurements should be studied in the future.