研究目的
To develop an analysis strategy to match the LenStar optical biometer measurements to A-scan ultrasonography for accurate axial dimension measurements in small animal eyes, specifically tree shrews, due to species-dependent differences in refractive indices.
研究成果
The proposed analysis strategy successfully matches LenStar measurements to ultrasonography in tree shrew eyes by using species-specific refractive indices, reducing errors significantly. This approach can be adapted to other small animal species with similar paired data, providing accurate axial dimension measurements for research applications.
研究不足
The LenStar was designed for human eyes, leading to inaccuracies in small animal eyes without correction. Freezing eyes for physical measurements may alter dimensions due to crystal formation. The method requires paired datasets from both techniques, which may not be feasible for all species or conditions. Refractive indices are wavelength-dependent and species-specific, necessitating recalibration for different instruments or species.
1:Experimental Design and Method Selection:
The study involved comparing LenStar biometer measurements with A-scan ultrasonography in tree shrew eyes. The strategy included manual delineation of intraocular interfaces using LenStar's EyeSuite software, exporting optical path lengths (OPLs), determining species-specific refractive indices through curve fitting, and converting OPLs to geometrical lengths (GLs) that match ultrasound values.
2:Sample Selection and Data Sources:
A total of 184 paired measurements from 66 northern tree shrews (Tupaia belangeri) were used, including normal and lens-treated eyes to vary axial dimensions. Data were split into 75% for fitting refractive indices and 25% for validation.
3:List of Experimental Equipment and Materials:
LenStar LS900 biometer (Haag-Streit AG), A-scan ultrasonography system with 15 MHz transducer, MATLAB software for data analysis, liquid nitrogen for freezing eyes, micrometer for physical measurements, Spectralis OCT (Heidelberg Engineering) for additional imaging.
4:Experimental Procedures and Operational Workflow:
Animals were anesthetized for ultrasound measures; LenStar measures were taken in awake, restrained animals. OPLs were exported from LenStar, refractive indices were estimated using MATLAB to minimize sum of squared residuals between LenStar OPLs and ultrasound GLs, and GLs were calculated. Validation involved comparing methods using relative errors.
5:Data Analysis Methods:
Linear regression and curve fitting in MATLAB were used to estimate refractive indices. Relative errors were calculated to compare LenStar internal analysis, a modified analysis, and the proposed strategy against ultrasound measurements.
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