| May 14th, 2009 | You Need Specs – Why? |
Here is some information about everyday eye conditions which may cause you to need prescription specs Myopia – Short sightedness, near sightedness Shortsighted people see well up close, but not at a distance. Distant objects are blurred, whilst close objects are in focus. DESCRIPTION The eyeball is longer than usual, making the eye "too powerful." The image is focused at a point in front of the retina. The higher the degree of myopia, the closer the distance at which the Shortsighted can visualise clearly.
SOLUTION Myopia can be corrected with a concave lens which is thinner in the center and thicker at the periphery. This type of lens system pushes the focal point back onto the retina and restores good vision at any distance.
HYPEROPIA – May be known by the terms long sightedness, far sightedness Farsighted people visualise far better at a distance than close up. Even though distant objects appear properly focused, the accommodation required to focus on close objects causes eyestrain. DESCRIPTION The eyeball is shorter than normal which means the eye is not powerful enough. The eye is said to be "too short" and the image is focused behind the retina.
SOLUTION Hyperopia is corrected using a convex lens which is thinner at the border and thick in the centre. This type of lens system brings the focus forward to the retina.
ASTIGMATISM People with astigmatism have poor nearby and distant vision. They do not sense the contrasts between horizontal, vertical and diagonal lines in the same fashion as the rest of us. Astigmatism is always accompanied by another visual impairment, such as Myopia, hyperopia and Presbyopia. DESCRIPTION Astigmatism is normally caused by an irregularly-shaped cornea which is slightly oval, rather than round, and oblong instead of spherical.
SOLUTION Astigmatism can be corrected using a cylindrical lens whose curvature offsets the corneal irregularity.
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