Myopia is also called nearsightedness or short-sightedness. It is a common vision defect and in past years could only be corrected by glasses – “coke bottle” glasses for severe myopia. More recently, contact lenses provided a more discreet correction, being invisible to others. Now it can also be permanently corrected with LASIK.
Myopic eyes cannot see clearly in the distance because they are bending light rays too sharply. The cornea (front clear surface) has a curvature that is too steep for the eyeball’s length front to back. The cornea and lens between them are focusing light from distant objects before it reaches the retina and that gives you a blurry image.
The more severe myopia is, the smaller the distance is at which objects can be clearly seen. On your prescription, severe myopia has a larger second number, such as 20/100 or 20/130. Mild myopia might be 20/40 or 20/60, with a lower second number that is nevertheless higher than 20.
If your prescription was 20/200, that would indicate legal blindness. It means that to see what a normal eye can see from 200 feet, you must be only 20 feet away. Since so many human activities require clear close-up and intermediate vision (driving, reading, computer work, household chores etc.), eyesight of 20/200 is fairly disabling. Most myopic people have better vision than that.
Hyperopic eyes have the opposite defect of myopic eyes. Hyperopia is also called farsightedness or long-sightedness. A hyperopic eye cannot see close-up objects clearly because it cannot bend light rays sharply enough. Light coming from close objects needs to be bent more sharply in order to focus on the retina. But light coming from far objects does not need sharp bending, and so distance vision is clear for a hyperopic eye.
Hyperopia can be corrected with glasses, contacts, and LASIK.
Hyperopia vs. Presbyopia In mid-life, everyone becomes a little more hyperopic, but it is not called hyperopia. It is called presbyopia and has a different cause. You can have 20/20 vision but you will still become presbyopic after about age 40 or 45. It seems that the lens become stiffer as we age, or the muscles controlling its curvature become weaker. The lens gradually loses its ability to change curvature and becomes more fixed in a shape appropriate for distance vision. Therefore close vision becomes blurry as we age.
