الفهرس 
MATERIAL AND MTHC0DSOnly 14 pages are availabe for public view
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Abstract
Pollution has become a major danger that has been, only recently, recognized as a global danger that must be dealt with. Air pollution in particular has hazardous effects on the human health; especially documented are the pathological changes it has on the lungs and the high mortality rate it causes.
Ocular irritation is well known to occur when there is dust or smoke. Most researchers directed their attention towards studying the subjective sensations resulting from the different air pollutants, and only few directed their work towards assessing the level of the different tear enzymes in relation to pollution.
In 1977, Egbert et al. Devised a new technique by which the epithelium of the conjunctival surface could be examined; they just took an imprint of the conjunctival epithelium on the filter paper then stained the picked up cells, and examined it under the light microscope. They called it a simple conjunctival biopsy. Because it was easy, simple, quick and atraumatic, it became popular in the diagnosis and follow-up of the different eye conditions, especially dry eye states. It also became and essential tool in the screening for the early detection of vitamin A deficiency.