The MS-39 device achieved high precision in both anterior and total corneal measurements the precision of posterior corneal higher-order RMS, astigmatism II, coma, and trefoil was lower. The mean difference in all aberrations was ≤ 0.05 μm. ICCs ranged from 0.846 to 0.989, from 0.432 to 0.972, and from 0.798 to 0.985 for the anterior, total, and posterior corneal aberrations parameters, respectively. Regarding interobserver reproducibility, all S w values were ≤ 0.04 and TRT ≤ 0.11. For the posterior corneal parameters, ICCs varied from 0.088 to 0.966. High repeatability was observed for anterior and total corneal parameters, with S w value 0.893, but not trefoil. Bland–Altman plots and 95% limits of agreement (95% LoA) were used to evaluate the agreement. The differences were evaluated by paired t-test. Within-subject standard deviation ( S w), test–retest repeatability (TRT), and intraclass correlation coefficient (ICC) were used to assess the intraobserver repeatability and interobserver reproducibility. Corneal aberrations were analyzed for the anterior, posterior, and total cornea surfaces. MethodsĪ total of 56 eyes (56 patients) were included in this prospective study. The completed devices are shipped world wide as the Tracey Technologies iTrace Combination Ray Tracing Aberrometer/Topographers.The aim of this study was to evaluate the measurements of corneal higher-order aberrations (HOAs) obtained by a new anterior segment optical coherence tomography (OCT) technique combined with a Placido topographer (the MS-39 device) in eyes with prior small-incision lenticule extraction (SMILE) and compare them to the measurements obtained by a Scheimpflug camera combined with a Placido topographer (the Sirius device). We currently manufacture the electronics under an OEM agreement with Tracey Technologies. Indus Instruments developed the electronics and the low level software for three generations of these ray tracing devices over a 10 year period. About a hundred such measurements are made across the eye in a fraction of a second and the data is used to compute the refractive index map of the eye.Ī novel feature of this instrument is the acousto-optic deflector that moves the laser beam across the eye without the use any moving parts. To accomplish this a low power infrared laser beam is sent into the eye and the deviation of position of the reflection from the retinal surface from the ideal position is measured to an accuracy within 2 microns (10^-6 meters). One of our customers, Tracey Technologies, Houston, TX, came up with the idea for a single beam refractometer based on retina ray tracing for measuring eye refraction distribution. These laser-based vision correction methods require accurate local parameter information across the eye to enable correction that achieves higher visual acuity. Modern laser technologies enable a more finely controlled cornea reshaping with an array of points of varying corrections across the eye. Conventional means of sight correction, like glasses or contact lenses, deal with global parameters of eye refraction.
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