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David Alonso-Caneiro, Stephen J Vincent, Brett A. Davis, Ross Franklin, Michael J Collins; Instrument for simultaneous assessment of tear film surface quality and subjective vision. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2498.
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To develop and test a custom-built instrument to simultaneously assess tear film surface quality (TFSQ) and subjective vision quality.
An infra-red illuminated Placido disk reflects a series of concentric rings from the tear film on the ocular surface to a camera that acquires a video recording at 10 fps. Simultaneously, the subject observed a static target (Siemens star) presented on a micro-display monitor via a beam splitter. The subject continuously adjusts an audible scale [0 (bad) - 10 (good)] to quantify their perceived image quality over time. By simultaneously recording the videokeratoscopic images and the subjective vision quality score, we were able to quantify TFSQ over the pupil region, while simultaneously acquiring the relative quality of vision. To test the system, a set of measurements were acquired for 3 subjects under controlled blinking (a blink every 10 seconds for 60 seconds duration) and suppressed blinking (no blinking for 30 seconds duration) conditions. For each condition, an initial practice session was undertaken, followed by two sets of measurements. The measurements were taken during soft hydrogel contact lens wear.
A correlation analysis between the TFSQ and the subjective vision quality score during the inter-blink interval reveals a strong correlation during the suppressed blinking conditions (mean Pearson's r=0.91, range 0.58 to 0.95, p<0.05). This correlation was still significant, although weaker, during the controlled blinking conditions at 6 blinks per minute (mean Pearson's r=0.62, range 0.51 to 0.71, p<0.05).
An apparatus and software methods to simultaneously record and analyze TFSQ and subjective vision was developed. The infra-red Placido disk light ensures that the pupil is not constricted during the measurements and that subjective vision quality scores reflect normal pupil sizes. The method may contribute to our understanding of the influence of tear film stability upon vision quality.
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