الفهرس 
Physiological aspects of tear filmOnly 14 pages are availabe for public view
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Abstract
The eye is covered by tear film which is optically clear and cotinuously to get rid of desquamated ceolls and foreign bodies.the tear film has a wetting properities and viscosity necessary for the health of the cornea.a decrease in its quantity or quality will cause several problems.the tear break-up timetest (but) is a simple non-invasive and useful test for clinical measurement of tear function.break-up time is a measure of the lengh of time the eye can be kept open before the tear film ruptures spontaneously (corneal wetting time).it is a measure of the relative insitability of the tear film.the but test was carried out on 1000 patients (1980eyes) whose ages ranged from 10 to 75 years.prior to the test all persons were subject to a complete ophthalmological examinations and the but test was carried on normal eyes.