Why is it better to wear contacts rather than glasses when you have myopia?

It may not provide "better" visual acuity to wear contacts (or have LASIK) but the latter can often provide a more "natural" kind of vision. The higher your glasses Rx if you are nearsighted, the more distortion you will experience in what you see, even if you can read 20/20 on the eyechart. The image size through glasses (concave lenses) appears smaller and further away, a kind of reverse telescope effect. This is barely noticeable with contact lenses or LASIK.

The reason is that the further a correcting lens is from the eye, the more it affects the image size. The reverse is true as well for farsightedness: the thicker the convex correcting lens, the bigger and closer an object appears. This is how a Galilean telescope works. Since contact lenses and LASIK exert their effect right on the eye (the cornea to be exact), the less "minification" or magnification occurs. If both eyes are the same Rx, you may not notice this change in image size because the distorted image size is equal in both eyes. But if you for some reason are quite myopic in one eye but not the other, the imbalance from wearing such different lenses in front of each eye can be very disturbing.

_Written by J. Trevor Woodhams, M.D. - Chief of Surgery, Woodhams Eye Clinic

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