Essay On Refractive Error

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Refractive error Refraction is the bending of light as it passes through one object to another. Vision occurs when light rays are bent (refracted) as they pass through the cornea and the lens. The light is then focused on the retina. The retina converts the light-rays into messages that are sent through the optic nerve to the brain to the occipital lobe in the cerebral cortex. The brain interprets these messages into the images we see. Refractive errors occur when the shape of the eye prevents light from focusing directly on the retina. The length of the eyeball (longer or shorter), changes in the shape of the cornea, or aging of the lens can cause refractive errors. Refractive error has may types but the most common types are myopia, hyperopia, presbyopia, and astigmatism. Nearsightedness (myopia): Nearsightedness (myopia) is a common vision condition in which you can see objects near to you clearly, but objects farther away are blurry. Pathophysiology causes : For the normal person, the cornea and lens are refracting the light rays and focusing on one point in the retina. However, in myopic person the eyeball is so long which make the light to focusing in front of the retina, also if the cornea is too carved…show more content…
And it has two types regular astigmatism and irregular astigmatism. Regular astigmatism occurs when Instead of the cornea having a symmetrically round shape (like a baseball), it is shaped more like a football, with one meridian being significantly more curved (steepest) than the meridian perpendicular to it. Irregular astigmatism occurs when the principal meridian are not perpendicular also Irregular astigmatism can result from an eye injury that effect the surface of the cornea, from certain types of eye surgery or from keratoconus, a disease that causes a gradual thinning of the

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