Abstract
Purpose :
A commercial instrument (HD Analyzer, Visiometrics SL) is capable of recording the double-pass Point Spread Function (PSF) of the eye by directing a narrow (2mm) near-infrared (780nm) beam onto the fundus and recording the aerial image of the retinal spot on a camera. Recently, this method was applied for the analysis of tear film dynamics
by means of time-resolved measurements of the PSF following a blink. In particular, temporal analysis of the PSF over twenty (20) seconds reveals information on the shape of the PSF (and the associated deterioration of retinal image quality).
The purpose of this study is to perform additional analysis on the double-pass PSF images to reveal tear film dynamics by means of light extinction.
Methods :
For analysis, we integrated the PSF over an angular range 0-10 minutes of arc essentially capturing the peak of the PSF. Images of the pupil were recorded simultaneously with the double-pass PSF. The pupil area was extracted and used for the normalisation of the PSF images. The time dependence of the intensity of the peak of the pupi-normalised PSF images revealed an attenuation consistent with wide-angle scattering.
We evaluated the method by analysing data from thirty-one (31) subjects from which sixteen (16) referred dry-eye symptoms.
Results :
As expected, dry eye patients exhibit a deterioration of retinal image quality over the first few (8-12) seconds following a blink. Dynamic simulations of perceived image quality demonstrate the character and the severity of these effects in combination with an objective, quantitative index of tear film quality. Extinction analysis revealed that an overall reduction of contrast as a result of wide-angle scattering may precede the PSF deterioration related to tear film break-up.
Conclusions :
This method may offer an objective tool for the quantification of the severity of tear film deterioration in dry eye patients. This objective method relies on the actual impact of tear film breakup on retinal image quality.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.