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S. Kasthurirangan, L. Vargas, S. Evans, V. Portney; Validity of iTrace Refraction Measurements in Pseudophakic Eyes. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5602.
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© ARVO (1962-2015); The Authors (2016-present)
The advent of novel intraocular lenses (IOLs) such as multifocal, aspheric and accommodative IOLs has brought a need to reliably measure refraction and ocular aberrations in pseudophakic patients. Aberrometers are becoming increasingly popular to understand the overall optical characteristic of a pseudophakic eye. The optical design of an IOL including refractive index, surface curvatures and optic diameter together with small pupils (4mm or less) in elderly patients may influence the performance of aberrometers. This study was designed to evaluate the performance and expand the scope of a common aberrometer (iTrace, Tracey Technologies, Houston) in measuring refraction in pseudophakic eyes.
Monocular subjective and objective iTrace refraction were performed under cycloplegia in sixty two (62) pseudophakic eyes including 15 subjects with a standard monfocal IOL and 16 subjects with the Synchrony Dual Optic Accommodating IOL. iTrace sphero-cylindrical refraction was externally calculated by exporting Zernike coefficients to a custom software in Matlab. The externally calculated sphero-cylindrical refraction was compared to iTrace measured refraction and subjective refraction. All objective measurements were performed for a 3 mm pupil. Additionally, refraction with +1D and -1D trial lenses placed in front of the eye was measured as a calibration procedure to evaluate the linearity of iTrace measurements.
iTrace measured and externally calculated refraction correlated very well (slope = 1.0 and intercept = 0.0; r2 = 1.0). The wavefront and refraction maps generated by iTrace could be exactly replicated externally with the custom Matlab software. Objective iTrace and subjective spherical equivalent refractive error correlated very well in all pseudophakic eyes (slope = 0.99 and intercept = 0.12; r2 = 0.81). Trial lens calibration showed linear change in refraction (r2 > 0.98) in 61 out of 62 eyes.
iTrace is a reliable instrument for measuring refraction in pseudophakic eyes. Trial lens calibration showed that small variation in refraction can be reliably detected with iTrace. iTrace data can be exported to an external software to independently calculate refraction, refractive maps and visual performance metrics.
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