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MJ Rondeau, G Barcsay, R Krishnamurthy, T Du, RH Silverman, DZ Reinstein, D Coleman; VHF Wide-Angle Ultrasound Biometry of the Anterior Segment for Toric Lens Placement . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4358.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: The successful use of both aphakic and phakic toric intraocular lens for correction of astigmatism is dependent on precise lens alignment with the astigmatic axis. This study models anterior segment ultrasound biometry and examines it's relationship to the axis of astigmatism. Methods:Twenty eight eyes of 14 healthy human volunteers were scanned using a custom wide angle VHF scanner. A series of 6 radial scans provided hemispheric coverage at 30 degree increments. Anamorphically corrected biometric angle to angle and sulcus to sulcus measurements were modeled using a direct least-squared method that constrains to an ellipse. Circular and directed statistical techniques were used to evaluate the data. Results:The semi-major axis as determined from the ultrasound data is not strongly correlated with the refractive or the keratometrically determined axis of astigmatism. Simulation studies show the ultrasound measurement and analysis technique to be a robust estimator. Conclusion:Measurements of elliptical conformation of the angle and sulcus suggest that assumptions concerning corneal curvature and the greatest diameter internal axis are incorrect. This finding has implications for future IOL haptic design and demonstrates the possible need for individual measurements to ensure proper lens placement.
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