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Opthalmology
Visual Acuity and Optical Defects PDF Print E-mail
Written by UrDocter   
Wednesday, 14 July 2010 12:14

If a personĀ  can read letters at 20 feet that are readable at that distance to all people with normal vision, that person's visual acuity, or "eyesight", is said to be 20/20. If, on the other hand, a person is barely able to read letters at 20 feet that are readable at 40 feet to all people with normal vision.

Astigmatism
Astigmatism is a condition characterized by "blemishid vision"; that is, instead of light rays striking the retina in sharp focus, they spread out over a more or less diffuse area. Astigmatism is caused by the unequal curvature of either the cornea or the lens, sometimes both. Because the cornea and lens, are never optically perfect, most of us experience some degree of astigmatism. To correct astigmatism, the ophthalmologist prescribes glasses that compensate for the faulty curvatures of the refracting surfabes

 
Chemical Injuries Of Ocular PDF Print E-mail
Written by dr. b3ty   
Tuesday, 15 December 2009 08:36

Chemical injuries of ocular are included in the most urgent of ocular emergencies. Bad effect severity depends on the solution pH, time of contact, quantity of solution, and ability to penetrate into ocular. Solution pH can be acidic or alkali.

Alkali burns are usually more destructive that react with fats to form soaps, which damage cell membranes, destroy the cell structure, epithelium, stroma and endothelium which allowing further penetration of the alkali into the eye and may continue to penetrate the cornea long after the initial trauma.

Last Updated on Tuesday, 12 October 2010 07:04
 


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Visual Acuity and Optical Defects

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If a personĀ  can read letters at 20 feet that are readable at that distance to all people with normal vision, that person's visual acuity, or "eyesight", is said to be 20/20. If, on the other hand, a [ ... ]


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