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Mikel Aldaba, Alejandro Mira Agudelo, Carlos Enrique Garcia-Guerra, John Fredy Barrera, Jaume Pujol; Tear film breakup time measurement based on corneal reflex interferences produced by dry spots.. Invest. Ophthalmol. Vis. Sci. 2017;58(8):471. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To test a new method for measuring the tear film breakup time based on interferences that appear on the corneal reflex. Dry spots in tear film cause abrupt height differences in the first eye surface, also the smoothness could be lost if corneal epithelium is exposed. Thus, the corneal reflex could present interferences caused by the phase differences, diffraction and speckle.
A setup for recording corneal reflex images was designed and built. In the illuminating path, a coherent lightsource (780nm laser diode) was projected onto the patient’s cornea after reflection in a beamsplitter. The corneal reflection was recorded by means of a CCD camera after passing through the beamsplitter and an achromatic doublet lens (f’=50mm). This lens produced defocused (2D) images of the corneal reflex, making easier the interference detection. The breakup was determined detecting the appearance of small structures, produced by interferences due to the dry spots in the recorded corneal reflex images. The measurement consisted on positioning and centering the patient, then recording the corneal reflex in the time between two consecutive blinkings. The obtained images were compared to simulations, besides the breakup times obtained with the proposed method and the conventional BUT method were contrasted.
Ten subjects with mean (±SD) age of 26.7±3.4 years participated in the study. The corneal reflex images after the first blinking were uniform in all cases. With elapsing time, the image is degraded and interference patterns appeared as a consequence of dry spots. The appearance of the interference structures depended on the subject, being needed only a few seconds in some cases while in other cases it took up to 1 minute. These times were well correlated with the breakup time measured with the BUT method, although longer times were found in the proposed method. The experimental images were in good agreement with the simulations, in both cases similar interference structures were obtained.
A method for the break up measurement of the tear film, based on corneal reflex interferences caused by dry spots, has been presented. The method is noninvasive, objective, simple to use and low-cost. It is oriented to clinical practice and could be implemented in regular ophthalmic devices (double pass or Hartmann-Shack), as the configuration and optical elements of both setups are nearly the same.
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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