The Optical Effects of Tear Film Disruption.
INDIANA UNIV AT BLOOMINGTON
Pagination or Media Count:
The most anterior optical surface of the eye has the greatest refractive power. Therefore, the quality of this surface is critical to retinal image quality and visual performance. Most optical texts identify the cornea as the first optical surface but in fact it is the tear layer. A smooth tear layer is considered optically essential and superior to the microscopically irregular cornea epithelium. Unlike the other optical surfaces within the eye, the tear film can vary tremendously from second to second as tear film changes occur between blinks. Although numerous studies have evaluated the change in tear film quality during periods of non-blinking little is know about the optical and visual effects resulting from changes in the tear film layer. The classic tear film models suggest that the precorneal tear film is composed of three layers, the superficial lipid layer derived from the meibomian glands, the middle aqueous layer provided by the major and minor lacrimal glands maintains ocular wetting, among other physiological effects, and the inner most layer overlies the cornea and conjunctival epithelial cells with mucous like material. Recent studies suggest that the tear film is composed of a mucin gel topped by a thin lipid film.
- Anatomy and Physiology