Clinical Comparison of Laser Ray Tracing Aberrometer and Shack-Hartmann Aberrometer

ABSTRACT

PURPOSE: To compare ocular aberrations measured with a laser ray tracing aberrometer (iTrace(R), Tracey technology) or a Shack-Hartmann aberrometer (Zywave(TM), Bausch & Lomb). METHODS: A total of 68 eyes were included in this study. After manifest refraction (MR) and pupil dilation, aberrations and phoroptor predicted refraction (PPR) were measured with the Zywave(TM) and iTrace(R) devices. The study group was subdivided into a more myopic group (-4.33 D). The root mean square (RMS) errors of the total high order, spherical, coma and 3rd~5th order aberrations were compared. RESULTS: The mean and SE of MR was -4.33+/-2.03 diopter (D), and that of the PPR was -4.20+/-2.13 D in iTrace(R) and -4.42+/-2.23 D in Zywave(TM). A paired-t test of the PPR and MR indicated that they were not statistically different. Zernike coefficients were expressed in the opposite sign in the 2nd and 4th order. The coma and spherical aberrations were larger in Zywave(TM). In a scattergram of each Zernike coefficient, the coefficient of determination (R2) was very low with higher order aberrations, with an exception for coma and spherical aberrations. The correlation of RMS error was greater in the less myopic group. CONCLUSIONS: Taking PPR values as a good reference of MR was a reliable method. For the HOA, only coma and spherical aberrations showed good correlations between Zywave(TM) and iTrace(R), and the correlations for HOA were decreased for the high myopic eyes.