Publication
Title
Refractive indices used by the Haag-Streit Lenstar to calculate axial biometric dimensions
Author
Abstract
PurposeTo estimate refractive indices used by the Lenstar biometer to translate measured optical path lengths into geometrical path lengths within the eye. MethodsAxial lengths of model eyes were determined using the IOLMaster and Lenstar biometers; comparing those lengths gave an overall eye refractive index estimate for the Lenstar. Using the Lenstar Graphical User Interface, we noticed that boundaries between media could be manipulated and opposite changes in optical path lengths on either side of the boundary could be introduced. Those ratios were combined with the overall eye refractive index to estimate separate refractive indices. Furthermore, Haag-Streit provided us with a template to obtain air thicknesses' to compare with geometrical distances. ResultsThe axial length estimates obtained using the IOLMaster and the Lenstar agreed to within 0.01mm. Estimates of group refractive indices used in the Lenstar were 1.340, 1.341, 1.415, and 1.354 for cornea, aqueous, lens, and overall eye, respectively. Those refractive indices did not match those of schematic eyes, but were close in the cases of aqueous and lens. Linear equations relating air thicknesses to geometrical thicknesses were consistent with our findings. ConclusionThe Lenstar uses different refractive indices for different ocular media. Some of the refractive indices, such as that for the cornea, are not physiological; therefore, it is likely that the calibrations in the instrument correspond to instrument-specific corrections and are not the real optical path lengths.
Language
English
Source (journal)
Ophthalmic and physiological optics. - Guildford
Publication
Guildford : 2015
ISSN
0275-5408
Volume/pages
35:1(2015), p. 90-96
ISI
000346769700012
Full text (Publisher's DOI)
Full text (publisher's version - intranet only)
UAntwerpen
Faculty/Department
Research group
Publication type
Subject
Affiliation
Publications with a UAntwerp address
External links
Web of Science
Record
Identification
Creation 06.02.2015
Last edited 18.07.2017
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