| |
 |
Eye
surgery |
|
Why vision defects?
In the eye that refract
the light correctly an object is projected on the retina, which is a condition
for a good acuteness of vision. The eye's refractive parts are the lens
and cornea.
When nearsighted
(myopia) you do not see well in long distances. The eye is too long in
proportion to the eye's refractive ability. The picture of a remote subject
is front of the retina. But with a concave lens you move the sharp picture
backwards to the retina.
When long-sighted
(hyperopia) you cannot see well in a close range. The eye is too short
in proportion to the eye's refractive ability. The picture of a remote
subject is front of the retina. But with a convex lens you move the sharp
picture forward to the retina.
Astigmatism
can exist independently if you are nearsighted or long-sighted. The cornea
is when not symmetrically, which makes the light refracting asymmetrically.
Therefor a sharp picture is not created on the retina. Regular astigmatism
can be corrected by a cylinder lens.
By presbyopia
you cannot see sharply in the close range. In old age the eye's ability
to accommodate decrease. Presbyopia usually starts in the 40's. Reading
glasses helps against presbyopia.
Read more about Monovision
Read more about LAPR
Read more about CLE
There are today
tree ways of correcting refraction error
1. Glasses
2. Lenses
3. Surgery
| |
1. Glasses
For many years, vision defects have been corrected by glasses with
lenses that either weaken the optical system of the eye - "minuses"
for shortsighted persons - or strengthen it - "pluses" for farsighted
persons. This simplest way of correcting vision defects is not sufficient
for all patients, though. Glasses meant for big defects are thick
and inconvenient. Even the best-fitted ones distort images and reduce
the field of vision.
For patients
with different refractive errors of the two eyes (anisometropia)
or with complex defects, it is not always possible to select glasses
that will assure vision acuity. Glasses can limit professional or
life activities such as sports. In their search to find correction
methods that would allow them to live a life without glasses, many
patients are also motivated by cosmetic reasons.
How you read your
glass prescription
|
|
|
|
|
|
|
Convex lens
|
concave
lens
|
|
|
2. Lenses
Contact lenses have been widely used as an optical method of correcting
vision defects. They successfully replace glasses and in many cases
offer the best way to improve the quality of vision. Wearing contact
lenses, shortsighted persons normally get a better eyesight acuity,
which sometimes comes as a surprise that they can see the world
in its true, not reduced dimensions.
There are, however,
a number of medical contra indications to wearing contact lenses.
Among them are: skin diseases, allergies, general disorders, e.g.
diabetes, chronic eye diseases and use of certain medications.
People who have
been wearing contacts for a long time can develop intolerance symptoms:
a sensation of a foreign matter, changes in the conjunctiva, allergies,
hyperaemia, which force them to resign from this method.
Many patients
find wearing contact lenses inconvenient, for it requires discipline
in following hygiene, doctor's instructions and care procedures
for storage and disinfection.
|
|
|
| |
|
| |
|
|
|
3. Surgical
methods of correction vision defects
Surgical methods
offer a chance to see better to patients for whom optical methods
failed to produce expected results, who cannot accept wearing glasses
or cannot wear contact lenses.
Surgical procedures
are performed for the following reasons:
Medical
- when neither glasses nor contacts offer sufficient improvement
in the quality of vision
Professional
- when glasses hinder a patient's professional career or full vision
acuity is required without optical correction e.g. for pilots
Cosmetic
- the most frequent around the world, considered by people who do
not want to wear glasses or contacts in their everyday lives.
|
|
| |
| |
|
|
