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Keiichiro Minami, Yosai Mori, Yasushi Kataoka, Shinichiro Otani, Naoto Honbou, Kazunori Miyata; Ray Tracing Intraocular Lens Power Calculation With Measurement Of Anterior Segment Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2012;53(14):6712.
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© ARVO (1962-2015); The Authors (2016-present)
Anterior segment optical coherence tomography (AS-OCT) provides topographic measurements of anterior and posterior corneal curvatures and corneal thickness. Use of posterior corneal curvature and central corneal thickness (CCT) in ray tracing intraocular lens (IOL) power calculation could improve the accuracy. We evaluate the accuracy in ray tracing IOL power calculation using AS-OCT measurements for normal cataract eyes.
With preoperative measurement of Placido topography and AS-OCT, predicted postoperative refractions were calculated in 3 settings: ray tracing calculation with Placido topography, ray tracing calculation with AS-OCT measurement, and the SRK/T formula using auto-refraction. Axial length was measured with a partial coherence interferometry, IOL Master (Zeiss). For 102 eyes of 70 patients who had the NY-60 (Hoya) implanted and obtained best corrected visual acuity of 0.15 logMAR or better, refraction errors from manifest refraction spherical equivalent at 1 month postoperatively were compared among three settings. Effects of eccentricity on the anterior cornea and posterior corneal curvature were also examined.
Mean refraction errors were -0.051, 0.016, and -0.001 D, respectively, while there was no significant difference (P=0.50). Results in the SRK/T were effected by eccentricity (P=0.002), that was found in ray tracing calculations. Ray tracing calculation with Placido topography was varied with posterior corneal curvature (P=0.0002), but with AS-OCT was not influenced.
Ray tracing with AS-OCT measurement was an accurate IOL power calculation for normal cataract eyes. Use of anterior corneal measurement in ray tracing calculation minimized effect of corneal eccentricity. Involving real measurement of posterior corneal curvature and CCT could retain the accuracy in ray tracing calculation for abnormal cornea cases
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