The Physics of Vision

Home         Background Info         Parts of the Eye         Refraction in the Eye      Image and Color         Eye Disorders and Fixes        Bibliography

Common Eye Disorders and Fixes Four common eye disorders are presbyopia, hyperonia, myopia, and astigmatism. These disorders are caused by the eye not refracting light properly. Presbyopia The eye has has the ability to see closer objects due to the process of accommodation. However this ability deteriorates as the eye ages, since the lens becomes less flexible. So instead of being able to adjust the focal length with the ciliary muscles the focal point is formed behind the retina which results in a blurry image. This is known as Presbyopia.  A common fix for this disorder is reading glasses, which uses a converging lens to decrease the focal length, causing the focal point to be produced on the retina again.        http://holbert.com/eye-disorders/ Hyperonia Hyperonia, or farsightedness, is when someone can see objects far away, but they cannot see objects up close. This is caused by the eyeball being too short, with respect to the focal length. When the eye tries to see an object close up, the lens can not accommodate enough to produce the image on the retina, so the focal point ends up behind the retina creating a blurry image.  http://holbert.com/eye-disorders/                                        A common fix for this is corrective lenses that are convex, or converging, which causes light rays to refract more inward, reducing the focal length, and placing the focal point onto the retina. Myopia Myopia, also called nearsightedness is when someone can see objects up close, but cannot see objects far away. This is causes by the eyeball being to long with respect to the focal length. This causes the focal point for farther away objects to be produced in front of the retina, which makes the image seem blurry.  A common fix for this disorder is corrective lenses that are concave, or diverging, which causes the focal length to increase, moving the focal point onto the retina.                                                                           http://holbert.com/eye-disorders/             Astigmatism Astigmatism is caused by the cornea of the eye being irregularly shaped, usually like the side of a football, which prevents the proper refraction of light and creates multiple focal points on the retina.This creates a blurry image. One common fix for this problem is corrective lenses that compensate for shape of the cornea. http://www.ullmaneye.com/full/micro.php