Imperfect Vision And How To Correct It
There are many reasons why an eye may not function properly. The most common of these are called refractive errors-conditions were the lens system of the eye will not focus light rays on the retina. Correction of these conditions is usually accomplished by the addition of either contact lens or a spectacle lens to the optical system of the eye.

An eye care practitioner will choose a convex, or plus lens, if the lens system of the eye requires more refractive power, a concave, or minus lens, if the refractive power of the system is to be reduced. Or, he may choose a cylindrical lens if the patient's eye refracts light unevenly because the cornea is 'egg-shaped' rather than 'ball-shaped'.

Far-sighted (Hyperopic) Eye
In a farsighted eye, parallel light entering the eye is focused behind the retina. The focal length of thelens system, that is the distance needed for refracted rays to focus at a point , is greater than the distance from the lens to the retina.
The farsighted eye is corrected with convex (+) lens. This adds sufficient power to the eye's optical systems to allow the the crystalline lens to remain in the flattened state normal for distance vision.

Near-sighted (Myopic) Eye
The nearsighted eye focuses light from a distant source on front of the retina. The focal length of the lens systems is shorter than the distance between the lens and the retina.
To correct myopia, a concave (-) lens is used to decrease the power of the optical system.

Astigmatic Eye
The astigmatic eye is unable to focus an entire image on its retina because of the 'egg-shaped surface of the cornea. Rays entering the North-South curve of the cornea may focus on the retina while those entering the East-West curve may not.
Both contact lenses and spectacle lenses are used to correct astigmatic vision.

Glasses or Contact Lenses
For millions of people contact lenses have brought a renewed freedom. The freedom to look good, feel good, and to enjoy a wider range of activities with safe, clear and comfortable vision.
Contact lenses are a very real alternative to spectacles for most types of eyesight problem and invariably offer equal if not better vision correction.
Gone are the days when getting used to wearing contact lenses meant days, sometimes weeks of perseverance. The latest ultra-thin water absorbent soft lenses are comfortable from day one and often barely noticeable after a few hours of wear.

For appearance and for all-round vision quality contact lenses win hands down.