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Daniel R Neal, Jason Hoy, kavita P Dhamdhere, Sanjeev Kasthurirangan, Wei Xiong, Thomas Daniel Raymond; Simultaneous wavefront and corneal topography measurement for tear film diagnostics. Invest. Ophthalmol. Vis. Sci. 2017;58(8):453.
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© ARVO (1962-2015); The Authors (2016-present)
Dry Eye is a condition that affects the tear film and thus quality of vision. Tear Film Break Up Time (TBUT) measured subjectively by slit lamp is the primary clinical metric to diagnose and monitor Dry Eye Disease. It would be useful to have additional, objective metrics to gauge tear film quality. The tear film quality can be evaluated using corneal topography, aberration, lipid layer, and osmolarity. The purpose of this study is to investigate tear film dynamics using simultaneous measurements of ocular wavefront aberrations and corneal topography.
A custom laboratory instrument was developed that incorporated both Full Gradient Corneal Topography (FGCT) and wavefront aberrometry (WF). Electronics were designed to control the illumination and camera timing through rapid multiplexing. Sequences of data were recorded with WF and CT measurements at ~14 Hz rate for 40 seconds. FGCT and WF measurements were acquired in a sequence, with subjects instructed to blink and then hold their eyes open for 10-35 seconds.
In ~40 seconds, 515 frames of FGCT and WF images were acquired on each subject. An example of the FGCT and WF images from near the beginning of a sequence is shown in Figure 1a, compared to the image (Figure 1b) from late in the sequence. Both WF and FGCT images have significant regions where the tear film has degraded the image spot quality after 12.6 seconds. Quantitatively, the WF RMS Zernike fit error has been shown to correlate with tear film break up. Figure 2 plots an example of this quantity as a function of time for one blink interval for the pupil area.
Tear film irregularity can effectively be measured using this process. A significant degradation in tear film quality was evident in both the FGCT and WF raw data. The WF Fit Error increases rapidly before a blink. Both WFFE and CTFE metrics increased as a function of time following a blink and correlate with the patient’s subjective description. These metrics are potential complements to subjective measures once normative ranges have been established.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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