For clear eyesight, the cornea (the clear
front window of the eye) and the lens (behind the pupil ) must properly
focus light rays on the retina which forms the back wall of the eye.
If your eye cannot focus image on the retina, then there is a refractive
error.
There are 4 common types of refractive errors: myopia, hyperopia,
astigmatism and Presbyopia.
Myopia ( nearsightedness ), hyperopia ( farsightedness), and astigmatism
are caused by differences in the length or the shape of the eye. On
the other hand, presbyopia (aging eye) occurs when the lens inside
the eye loses its focusing ability for near vision.
Nearsightedness, farsightedness, astigmatism and presbyopia usually
can be corrected with eyeglasses, contact lenses, or refractive surgery.
Read the following articles to find out more about the causes and
treatment of these four types of refrective errors.
Myopia (Nearsightedness)
In myopia, the eyeball is too long for the normal focusing power of
the eye. As a result, images of distant objects appear blurred...read
more
Hyperopia (Farsightedness)
In this condition, the eyeball is too short for the normal focusing
power of the eye. In children, the lens in the eye accommodates for
this error and provides clear vision for distance and usually near
viewing, but with considerable effort that often causes fatigue and
sometimes crossed eyes (strabismus)...read
more
Astigmatism
Astigmatism results primarily from an elongated shape of the front
surface of the cornea, which usually causes vision to be blurred or
distorted to some degree at all distances. Persons with astigmatism
typically see one direction of lines more clearer than the lines 90
degree away from it...read more
Presbyopia
As people age, they often experience difficulty in focusing their
eyes for reading and close work. This condition is called presbyopia
( aging eyes). It is easily corrected with glasses...read
more
