Refractive
errors and treatment
What is refractive error?
The
function of the eye is to see
clearly the objects around us. The inability of the eye to accurately
focus the rays of light coming from distance on the retina is called
refractive error. This condition may be either because the eye is too
short or long in length, or because the cornea or lens does not have the
required refractive power. There are three types of refractive errors:
Myopia
(near-sight): this is the condition in which the eye is too
long and the light is focused in front of the retina. Distant objects
are blurred but the near objects are seen clearly. The eye has too much
optical power and to correct it the optical power is reduced by either
minus glasses or contact lenses, or by surgery.
Hypermetropia
(long-sight): this is the condition in which the eye is too
short and the light is focused behind the retina. The eye has less
optical power than is needed. When young the eye can use the lens within
the eye to compensate, but reading glasses are needed at a relatively
early age. Later, distance glasses (plus) are needed as well, such that
glasses for distance and near are required.
Astigmatism:
this is the condition where the eye does not focus the light evenly,
usually due to the cornea of the eye being more curved in one direction
than the other. It may occur on its own or may be associated with myopia
or hypermetropia.
What is
Presbyopia?
Presbyopia is the normal aging process, where the lens progressively
loses its capacity to increase its power for near vision (loss of
accommodation). The distance vision may be normal, but the near vision
becomes blurred with age greater than about 45 years. This is corrected
by wearing reading glasses (plus) for the near work. This condition may
occur in itself or may be present alongwith pre-existing myopia,
hypermetropia or astigmatism.
What are the ways of treating refractive
errors?
The refractive errors may be treated by either of the following ways:
- Glasses: this is the simplest and most popular
way of correcting refractive errors
- Contact lens: this option is cosmetically much
better though the maintenance and cleaning of contact lenses may be
cumbersome. There is also a slight risk of infection to the cornea,
if the contact lenses are not cleaned properly before use.
- Refractive
surgeries: these are increasingly becoming popular
with the advent of more predictable laser treatments.
