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Jayoung Nam, Nikole L. Himebaugh, Arthur Bradley, Haixia Liu, Carolyn G. Begley, Larry N. Thibos; The Scale and Spatial Distribution of Optical Aberrations That Accompany Tear Break-up. Invest. Ophthalmol. Vis. Sci. 2012;53(14):163.
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Tear film break-up (TBU) causes local, and often highly irregular changes in tear film thickness. We examined the spatial correlation between TBU and the associated optical anomalies on three different spatial scales.
Ten subjects refrained from blinking while the time course and patterns of TBU were sequentially observed using sodium fluorescein (FL), retroillumination (RI), and Shack-Hartmann (SH) aberrometry. Wavefront error (WFE) maps were developed using Zernike polynomials, as well as a local zonal analysis of the SH data. The difference between these approaches reveals the very high order aberrations beyond those captured by standard modal fitting methods. Also, SH spot blur was quantified as a means for estimating fine scale optical perturbations in the tear film (microaberrations). Spatial correlation between TBU and optical aberrations was determined by computing the percent overlap of dark regions of the FL images and the anomalous regions of either the RI or SH images.
Increased aberrations over all three spatial scales were present in the regions of TBU. TBU induces an irregular pattern of phase advances across the pupil, with accompanying increases in lower order aberrations, higher order aberrations, very high order aberrations and micro-aberrations. Larger increases occur at the finer spatial scales.
The optical aberrations following cessation of blinking correspond temporally and spatially with TBU and reveal tear thinning and exposure of a rough optical surface. In addition to optical aberrations, scatter develops in the areas of TBU, all of which will contribute to image degradation and visual disturbances following TBU.
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