Laser eye correction (e.
g.
LASIK, Epi-LASIK, LASEK and PRK) works by slightly altering the curvature of the cornea.
The cornea is the curved clear window at the front of the eye.
All that the laser can do is to remove tissue.
To correct short sight (myopia) the laser flattens the centre of the cornea.
To correct long sight (hyperopia) it makes the centre more prominent by removing tissue in a ring pattern around the centre.
There is a limit to how much tissue can be removed safely.
This is why some people are not suitable for laser eye correction.
In other words not all eyes can be "fixed" with laser and this is usually because the prescription is too high.
However there are alternatives to laser.
One of these is "Refractive Lens Exchange".
The eye is like a camera.
Apart from the cornea at the front of the eye the other main focusing part of the eye is the lens.
The natural lens of the eye cannot be seen without special instruments but it is positioned within the eye just behind the pupil.
This natural lens can be surgically removed and replaced with an artificial lens, called a "lens implant".
The power of the "lens implant" is chosen to give the eye the correction that is wanted.
With this operation almost any degree of short or long sight can be treated.
In other words "Refractive Lens Exchange" can be used to "fix" eyes that cannot be corrected using laser treatment.
The surgical procedure for "Refractive Lens Exchange" is the same as a modern cataract operation.
This means it uses tried and tested technology.
It is not a new or experimental treatment.
It is using a proven technique for a new purpose.
A cataract is where the natural lens of the eye has become cloudy obscuring vision.
The treatment is to remove the natural cloudy lens and replace it with a clear artificial lens.
In "Refractive Lens Exchange" the natural lens is still clear and healthy but is removed and replaced with a lens implant in order to correct a focus error (refractive error) of vision.
For this reason, and to differentiate it from a cataract operation, it is also sometimes called "Clear Lens Extraction" Refractive Lens Exchange is best suited to those over 50 years of age.
This is because in youth the natural lens of the eye is pliable and gives the eye adjustable focus providing both distance and near vision.
This ability is lost with aging and is why many require reading spectacles from mid-40's onwards.
Removing the lens much before this age will rob the patient of natural focus adjustment which is difficult to restore with a lens implant.
However for "the more mature" where near focus has already been lost anyway this is less of an issue.
Where an attempt is made to assist both near and distance vision the procedure is sometimes called "Presbyopic Lens Exchange" or "PRELEX".
This can be achieved in several ways.
One eye may be corrected for distance vision whilst the other is set for near vision.
This is called "monovision".
Alternatively some surgeons use multifocal lens implants, although these can reduce the quality of vision.
Adjustable focus lens implants exist but as yet they do not usually restore a focus adjustment equivalent to that in youth.
For more details see: http://www.
lens-exchange.
co.
uk The information within this article is for general interest only.
These are the personal views of Consultant Ophthalmologist Mr.
C J Heaven.
If you have a problem with your vision then always seek the advice of your own eye specialist.