Tear-film dynamics by Fourier analysis in double-pass images

SÁNCHEZ ROBERTO FRANCISCO; CALDERARI LUIS; ISSOLIO, LUIS

Conferencia; Optics, Photonics & Upcoming Methods and Applications (OPUMA) Conference; 2020

Universidad Nacional Autónoma de México (UNAM)

Introduction. The double-pass method allows an integral evaluation of the retinal image quality, taking into account the degradation due to both optical aberrations and intraocular scattering [1].Objective. The objective of this work was to analyse the dynamics of the double-pass image (DPI) as a measure of the tear-film stability.Methodology. A study of the dynamics of the DPI during tear-film rupture was carried out in two groups of voluntaries, a control group with normal subjects (n = 4) and a study group where we sought to simulate dry eye conditions in normal subjects using disposable contact lenses (n = 3), which quickly degrades the tear-film [2]. DPI series were recorded every 0.5 seconds while the subject avoided blinking as long as possible. From the DPIs, a new scattering metric called FDSI (Frequency Domain Scatter Index), was computed based on the Fourier analysis of these images, and the tear-film stability was analyzed by the ratio (FDSI-FDSI0) / FDSI0, where FDSI is the measurement in each image and FDSI0 is the measurement for the first image after the last blink.Results. In the control group the ratio (FDSI-FDSI0) / FDSI0 remained steady for all the time that the subject could avoid blinking (about 40 seconds), with a mean value of 0.1; while in the study group the ratio showed a significant increase before 10 seconds (p