Abstract
PurposeTo evaluate the influence of low signal-to-noise ratio (SNR) of axial length measurement, achieved using IOLMaster, on prediction of target refraction.MethodsA total of 131 eyes of 131 patients who underwent phacoemulsification with posterior chamber lens implantation were enrolled. Preoperative axial length measurements were performed with the IOLMaster 500 (Carl Zeiss Meditec, Germany); preoperative SNR values were used to divide the eyes into three groups (Group 1; SNR <10, Group 2; 10 ≤ SNR <50, Group 3; 50 ≤ SNR <100). One month and 6 months after cataract surgery, the manifest refraction spherical equivalents (MRSE) were measured. The mean numeric errors (MNE), the mean of the difference between postoperative MRSE, and preoperative target refraction, using the various intraocular lens (IOL) formulas, were calculated and compared among the three groups.ResultsOne month after cataract surgery, postoperative MRSE was more hyperopic than preoperative target refraction, calculated by the Haigis formula in group 1, and by the SRK/T formula in group 2. After 6 months, for all formulas in group 1, there were significantly hyperopic results (approximately 0.35 diopter). Upon comparison of MNE among the three groups, group 1 was statistically significantly different from the other groups by Haigis formula.ConclusionsWhen the SNR values in biometry, using IOLMaster, are <10, careful attention should be given to determining IOL power, as postoperative spherical equivalents are more hyperopic than preoperative target refraction by IOL formula.
Highlights
The precise measurement of the axial length (AL) and corneal power is important in the calculation of intraocular lens (IOL) power.[1, 2] As commonly known, an inaccurate AL measurement results in crucial errors in postoperative refraction; more accurate measurement of AL has been required to respond the increasing demand for cataract surgery as a refractive correction.[3]
One month after cataract surgery, postoperative manifest refraction spherical equivalents (MRSE) was more hyperopic than preoperative target refraction, calculated by the Haigis formula in group 1, and by the SRK/T formula in group 2
When the Signal-to-noise ratio (SNR) values in biometry, using IOLMaster, are
Summary
The precise measurement of the axial length (AL) and corneal power is important in the calculation of intraocular lens (IOL) power.[1, 2] As commonly known, an inaccurate AL measurement results in crucial errors in postoperative refraction; more accurate measurement of AL has been required to respond the increasing demand for cataract surgery as a refractive correction.[3]. Signal-to-noise ratio (SNR) is an indicator of the accuracy of AL measurement by the IOLMaster. A high SNR value reflects higher accuracy and could help inexperienced operators choose IOL power .[16] In the early usage of IOLMaster, the averaging of consecutive scans was used to increase SNR, but had a limitation in that actual signals were low in amplitude. After development of version 5, the composite method (achieved by digital processing of signals of multiple measurements) had improved SNR.[17,18,19]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
