REFRACTIVE ERRORS WITH A NORMAL EYE, THE CURVATURE OF THE CORNEA, THE POWER OF THE LENS and the length of the eye are proportioned and perfectly matched to cause refracted (bent) light rays to come to a perfect focus point directly on the central retina. Refractive error refers to when the optics of the eye are not correctly proportioned or matched, resulting in blurred vision. Refracted light passes through the lens defining images just short or beyond the central retina, and with astigmatism creates multiple points of focus, causing distortion in the images perceived. MYOPIA In myopia or nearsightedness, the steep curvature of the cornea and long length of the eye, or both, cause the light rays to focus in front of the retina. The optical power of a myopic eye is too strong, resulting in near images appearing clear and distant images appearing blurred. HYPEROPIA In hyperopia or farsightedness, the flatness of the cornea and short length or the eye, or a combination of both, cause the point of focus of the eye to fall beyond the retina. The optical power of the hyperopic eye is inadequate or weak making objects that appear close blurred. Sometimes even objects in the distance can be blurred. > Return to top ASTIGMATISM With astigmatism, both the cornea and the lens have an irregular curvature, causing light to focus on more than one point of the eye, none of which accurately represent a perfect image. With an astigmatic cornea, instead of having a spherical curve like the shape of a basketball, the curvature is more oval like the shape of a football. Most corneas affected by astigmatism have two curves, a steeper curve and a flatter curve, which generate the multiple points of focus. Astigmatism often occurs in combination with myopia or hyperopia. The result is blurred, distorted vision at near or far distance. > Return to top PRESBYOPIA Presbyopia is a natural occurrence that affects individuals at about 40 to 60 years of age when the internal lens of the eye losses its ability to change its focusing distance, known as accommodation. The lens thickens as the eye matures and becomes less flexible, increasing its ability to focus near. As presbyopia develops, close-range activities such as reading a book or viewing a computer screen may become increasingly difficult requiring reading glasses or bifocals. > Return to top Our Practice l Services l Publications l Map & Directions l Contact Us l Privacy Policy Cataracts l Cornea and External Diseases l Corneal Transplants l Refractive Errors Refractive Surgery l Optics All contents © copyright 2002-2004 Corneal Consultants of Colorado, P.C. All rights reserved. Development by Mindshare HDV. Normal Eye Myopia Hyperopia Presbyopia