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Diagnosing A Refractive Error - Essay Example
A large number of people suffer poor vision which is due to uncorrected refractive errors. These people are in need of correction of their refractive errors with properly tested spectacle prescriptions.
Autorefractometer has the drawback of being an expensive instrument and is not available everywhere, while a correct retinoscopy depends largely on the skill of the performing person and needs lot of proper training.
Being myopic, you would be able to see better at near, while objects become progressively blurrier with distance.
"Hyperopia, the hyperopic eye is deficient in refractive power. The rays from infinity are not refracted enough; thus the point of focus is behind the retina. The eye lacks plus power." (Handbook of Refraction, George E. Garcia, M.D., Pg 23) This is caused either by the cornea being too flatly curved, the axial length of the eye being too short, or a combination of both.
'Astigmatism is a condition in which rays of light are not refracted equally in all meridians. For the purpose of classification, an astigmatic eye is assumed to have two principle meridians that are usually at right angles to each other. (Handbook of Refraction, George E. Garcia, M.D., Pg 35)
Astigmatism is caused by the abnormal shape of the eye. Like a football, distorted in shape, being flatter along one meridian and steeper along the other. The clarity of vision would be affected at all distances. If your astigmatism is oriented vertically, there will be selective blurring of vertical lines.
"Presbyopia is a normal condition associated with age. ...