Purpose:
To evaluate artificial tear film thickness on model eyes with contact lenses using a new optical reflectometry method.
Methods:
Tear film thicknesses in a model eye with a contact lens are evaluated using optical reflectometry method. A model eye wearing a contact lens with artificial tear films are illuminated by a fiber coupled broad band light (350nm to 1000nm) from a Tungsten Halogen light source. The return reflected light from the tear film boundaries with spectral dependent reflectance information is fiber coupled to an optical spectrometer. With known material refractive indices of the tear films and contact lenses, the curve fitting of the spectrum interference reflectance pattern acquired by the spectrometer yields the tear film thickness. Through time dependent reflectance data capturing and thickness determination, the tear film thinning dynamics including thinning rate and tear film breakup thickness are determined. Using fiber coupled optical reflectometer system facilitates compact packaging and user friendly handling. In addition, a Galvo scanner is introduced to the system for fast automatic optical alignment of the optics and future extension of the method to large area full eye tear film measurement. The measurement data collection is fast of about 5 msec making the measurement insensitive to potential eye motion. The measurement has a high resolution of better than 10 nm and is very valuable for dry eye disease study.
Results:
Tear film thickness measurement on model eyes with and without different contact lenses has been carried out. Minimum measured team film thickness is currently at 0.85 µm. Videos of the tear film thinning process has been captured. Differences in tear film thinning dynamics have been found for different contact lenses.
Conclusions:
This study shows the effectiveness of optical reflectometry for evaluation of tear film dynamics in a model eye. With fast data collection measurement insensitive to eye motion, the technique has potential for tear film evaluation on a human eye.
Keywords: contact lens • cornea: tears/tear film/dry eye • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)