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Y. Yang, J. Shao; Location Shift of the Thinnest Corneal Point After Myopic LASIK. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3362.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate the location of the thinnest point of the cornea and evaluate its change in location after myopic LASIK(laser in situ keratomileusis)utilizing the optical pachymetry.
The OrbscanIISystem was used to measure 410 eyes of 207 patients undergoing myopic LASIK to compare the pre-operative versus the post-operative location of the thinnest point of the cornea relative to three different reference points(the orbscan IIsystem default origin,the pupil center (line of sight),and the visual axis(fixation point).
Using the system default origin as the reference point, the location of the thinnest corneal point was located in the infero-temporal quadrant in approximately half of both the pre-operative(52.6%) and post-operative eye(49.5%). Using this same reference point, the thinnest corneal point moved nasally and superiorly from pre-op compared to post-op(mean distance:0.258±0.343mm). The results in terms of location and shift in thinnest corneal point after myopic LASIK utilizing the pupil center and visual axis as the reference ponits, respectively, were very similar to those seen utilizing the system default origin as the reference point. However, further analysis showed that the ratio of the post-operative distance of the thinnest point the the origin divided by pre-operative distance of the thinnest point to the origin was significantly higher using the system default and visual axis as the reference point(0.733 and 0.741,respectively) thanthe same ratio calculated utilizing te pupil center as the reference point(0.666).
After myopic LASIK, the thinnest corneal point tends to move superonasally from the inferotemporal quadrant as measured by the OrbscanIIoptical pachymetry system. Furthermore, the post-operative distance from the thinnest corneal point to each of 3 reference points (system default, pupil center and visual axis) is significantly smaller than the pre-operative distance of the thinnest point of the cornea to these same reference points. Because the pupil center is utilized as the reference point for most excimer laser tracker, including the laser in our study, the thinnest corneal point moves closer to the pupil center than the visual axis or system default origin after LASIK.
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