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ASTIGMATISM
1. Introduction: What is Astigmatism? Astigmatism refers to minor disability causing from inability of the eye to create an image at a single focus point on the cornea surface, or the ametropia of having multiple focus points. The cornea refers to transparent surface that covers forefront part of the eyeball, which we commonly refer as the iris.
The transparent cornea lets lights easily pass through the surface, and is shaped like a convex lens so that the incoming light rays toward our eyes can be bent to form an image at a single point of the retina. The bending of light rays happen within the cornea and crystalline lens, with the cornea handling 2/3, and the crystalline lens handling 1/3 of the total process.
As described above, the cornea that resembles single sided convex lens, displays a symmetrical shape unless the person does not have astigmatism. However, astigmatism causes distortions in the symmetry, transforming the cornea in peculiar shapes. To ease understanding, one can imagine the distorted shape of the cornea as partially dissected basketball, or rugby balls.
When the cornea has been distorted to the shape of rugby balls, the focus point that is created by light rays departing from a single point differs by the orientation of the direction of the light. If we draw imaginary horizontal line from the center of the cornea and assume point to be 0 degrees, the light rays from 0 degree direction and 90 degrees direction does not meet at single point due to distorted shape, and generates a blurred vision. Generally, the astigmatism axis will form a 90 degree angle. For example, if one astigmatism happens at 15 degrees direction, the other astigmatism axis will form in 105 degrees direction.
Manufacturing Astigmatism Colored Contacts involves taking both myopy and astigmatism level into account. Therefore only with precise measurement of one's condition from ophthalmologist can one have the perfect colored contacts produced. In order to prevent the side effects from wearing colored contacts, one must purchase the right lenses after having allergic reactions tested out from optical centers. Moreover, contacts must be maintained with hygiene, with constant washing and cleansing of remnant protein tissues. The time worn must not exceed 6 to 8 hours. Nighblind people or overnight drivers must not wear colored contacts, since the contacts may blur their sights during nights. Unlike hyperopia or myopia, in which the formed single focus does not meet the surface of the retina, astigmatism blurs vision because light rains from a single point from a distance does not meet at a unified focus point after passing through the cornea and the crystalline lens.  |
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