Calibration of axial length measurements with the Zeiss IOLMaster
- 1 July 2005
- journal article
- Published by Ovid Technologies (Wolters Kluwer Health) in Journal of Cataract & Refractive Surgery
- Vol. 31 (7), 1345-1350
- https://doi.org/10.1016/j.jcrs.2004.12.066
Abstract
Purpose: To study the conditions for consistent axial length measurements with partial coherence interferometry (PCI) performed with the Zeiss IOLMaster. Setting: University Eye Clinic, Aarhus, Denmark. Methods: A consecutive, unselected series of 1289 cataractous eyes were measured with the optical technique of PCI according to the IOLMaster as well as with conventional (contact) A-scan ultrasound (US) for the measurement of axial length. For each PCI reading, the signal-to-noise ratio (SNR) was recorded and used for comparison with the US measurement. All patients had routine phacoemulsification with implantation of an intraocular lens (IOL). In 284 cases, the patients were reexamined 2 to 3 months after surgery and the axial length was again measured using PCI. The readings of the IOLMaster, which had been calibrated against immersion US from the manufacturer, were recalculated to represent the true optical length and used in the analysis of the consistency of the measurements. Results: Not all readings obtainable with the IOLMaster were of good quality, and large differences with conventional US were found. The error between US and PCI decreased significantly with increasing SNR, showing a minimum error at an SNR value above 2.1. The SNR correlated significantly with the visual acuity with considerable scatter, however. Excluding readings with a poor quality (SNR r = 0.99), showing a mean difference of 0.08 mm ± 0.12 (SD). The difference was highly significantly different than zero (P<.001) and may be explained by a higher refractive index of the biological lens than assumed in the original calibration of the IOLMaster. Conclusions: The quality of the axial length readings of the IOLMaster was influenced by the SNR value. However, with proper SNR evaluation and recalibration of the PCI measurements, it is possible to achieve consistent PCI readings with little variation between preoperative and postoperative measurements. These results are promising for a higher accuracy of the IOL power calculation.Keywords
This publication has 11 references indexed in Scilit:
- Influence of operator experience on the performance of ultrasound biometry compared to optical biometry before cataract surgeryJournal of Cataract & Refractive Surgery, 2003
- IOLMaster biometry: refractive results of 100 consecutive casesBritish Journal of Ophthalmology, 2003
- Accuracy and reproducibility of biometry using partial coherence interferometryJournal of Cataract & Refractive Surgery, 2002
- Immersion A-scan compared with partial coherence interferometryJournal of Cataract & Refractive Surgery, 2002
- Refractive outcome of cataract surgery using partial coherence interferometry and ultrasound biometryJournal of Cataract & Refractive Surgery, 2002
- Reproducibility of optical biometry using partial coherence interferometry: intraobserver and interobserver reliabilityJournal of Cataract & Refractive Surgery, 2001
- The repeatability and accuracy of axial length and anterior chamber depth measurements from the IOLMaster™*Ophthalmic and Physiological Optics, 2001
- Pseudophakic correction factors for optical biometry.Albrecht von Graefes Archiv für Ophthalmologie, 2001
- Comparison of immersion ultrasound biometry and partial coherence interferometry for intraocular lens calculation according to HaigisAlbrecht von Graefes Archiv für Ophthalmologie, 2000
- Partial coherence interferometry: a novel approach to biometry in cataract surgeryAmerican Journal of Ophthalmology, 1998