Temporal Changes of Tear Film Break-Up Observed by a Real Time Hartmann-Shack Wavefront Aberrometer

Abstract

Abstract: : Purpose: Wavefront aberrations were induced by tear film break-up(Koh S, et al, Am J Ophthalmol, 134, (2002) 115-7). To develop a novel method for measuring a onset time of the break-up and its rates, higher-order wavefront aberrations were measured continuously after blinking using a Hartmann-Shack wavefront aberrometer. Methods: Wavefront aberrations up to 6th order for 4 mm pupil were measured for four eyes of four normal subjects using a Hartmann-Shack wavefront aberrometer specially built for this purpose. The aberrometory was performed on each case once every second up to forty seconds under topical anesthesia. We plotted RMSs of higher-order wavefront aberration(HWA) versus temporal duration after blinking for each case. The sequence of the points in each plot were divided into a steady state, in which the slope of the regression of this group of points was relatively flat, and a break-up state, in which the slope was relatively steep. We set that the onset of the break-up was the border of the two states and the temporal rate was the slope of the break-up state. Results: Four sequences we measured were easily divided into two states respectively, including the sequence shown in Fig. 1. The onset times for four cases were 11.3, 15.8, 8.0 and 8.0 s. The rates of the break-up were 8.1, 3.7, 7.4 and 0.7 nm / s.  

Keywords: cornea: tears/tear film/dry eye • optical properties • cornea: clinical science