|
|
|
| University of Rochester | |
|
|
Dry EyeThe cornea which is the most outer surface of the eye provides most of the optical power to the eye. However, biological tissue alone provides poor optical quality due to its rough surface profile. The tear film, consisting of 90 percent aqueous material held in place by a 0.1 µm thick layer of lipid, forms the first surface of the eye where the change in the refractive index is the greatest. A uniform layer of tear film gives the cornea a smooth surface to refract light properly and to form high quality images on the retina. However, tears are also dynamic and evaporate. Understanding how the tear film affects the optical quality of the eye has both clinical and scientific significance. This may improve diagnoses for tear film disorders. 1. Measuring changes in the aberration caused by tear film dynamicsOur understanding of the tear film structure and its optical properties is still rather elementary. There is still no single test that can perform a complete evaluation of the tear film. The process of measuring aberrations induced by the tear film is difficult because many ocular aberrations are not only dynamic but highly irregular as well. As a result, many investigators have had limited success in quantifying these aberration changes using commercially available instruments. We implemented a high resolution Shack-Hartmann wavefront sensor equipped with a custom-made corneal topographer and demonstrated its effectiveness in measuring the tear film induced aberrations changes in eyes as shown in below. Both the wavefront sensor and topographer are designed to use near infrared light illumination sources to avoid artificial stimulation of natural tear secretion process. 
The following movies recorded with the wavefront sensor show tear film breakup patterns in a healthy eye due to lengthy non-blink interval. Both topography and wavefront spot patterns show irregular tear film breakup at the end of the movie. Dynamic changes in the aberration due to this tear film breakup can also be computed as shown the other movies. We also compute other retinal image quality metrics such as PSF and area MTF with the measured aberration to characterize tear film behavior and objectively quantify tear film breakup time. We found that tear film breakup pattern is variable between subjects and even more irregular in patients with dry eye syndrome.
You need to upgrade your Flash Player
2. Collaborative dry eye researchFor a better understanding of the tear film, we formed a research team in which clinicians and basic scientists in other research laboratories at the University of Rochester participate. In this collaboration, we are currently developing additional imaging modalities, ellipsometer and anterior segment real time OCT that provide information on thickness and refractive index of the lipid layer and tear film. Our goal is to combine these one or two imaging systems with the wavefront sensor to characterize differences between normal and dry eye patients, and even between dry eye patients with different symptoms. | |
| |
