Considering laser corrective eye surgery? Beware... (LASIK Treatments)

Member Name: sgrup

Product:	LASIK Treatments
Date:	25/02/01 (2957 review reads)
Rating:

Advantages: few for the patient - considerable for the industry behind these surgeries

Disadvantages: too risky and success is definitely not guaranteed

The laser corrective surgery for the eye has not achieved as much popularity as predicted a few years ago. The reason for this is not only that people are scared of having surgeons messing about with their eyes but because the results obtained from these corrective surgeries has not been overwhelmingly great. Indeed there is a strong (probably increasing) community in the field who are strongly against the corrective eye surgery in its current forms.

Let me start off with a brief description of vision and vision correction in general. The eye is a simple optical system - the cornea (outermost surface of the eye) and the lens focus light coming from an object onto the retina (back part of the eye) which acts light a photographic film. The image formed on the retina is then processed by the brain to produce the image that we actually see. However the eye is far from being a perfect optical system - it introduces irregular deviations to the light entering it so that the image produced on the retina is a blurred copy of the original object. These deviations are known as aberrations. In a person with good eyesight, these aberrations are small and the blurring is not very significant. However in some people these aberrations are considerable and the image formed on the retina is of a rather poor quality. These people need some form of correction to enhance the image produced on the retina. Spectacles and contact lenses are the most common forms of vision correction - they try to redirect the light so that the blurring of the image on the retina in minimised. However the eye produces a large number of different aberrations and spectacles and contact lenses can only correct two of these aberrations, known to the optometrists as defocus (myopia or hypermetropia) and astigmatism. (Myopia and hypermetropia are also known as short- and long-sightedness respectively). In most eyes, correcting for these two aberrations is enough to improve vision substantially, but these
are not the only aberrations in the eye.

Laser corrective eye surgeries also attempt to correct for these two aberrations, but the mechanics of how this is done is clearly very different from spectacles or contact lenses. LASIK is the most common of these surgeries. Surgeons try to change the shape of the cornea so that light is correctly focused on the retina - but unfortunately this procedure is not as easy as it may sound. The surface of the cornea is not a perfect sphere or any other perfectly smooth surface, but it is irregular. This makes the process of understanding what corrections are necessary difficult. Besides that, even if it were possible to precisely predict what shape of cornea is required, there is still the challenge of actually producing that exact shape during the surgery.

The main problems with the LASIK surgery are briefly explained below:

(1) Many people believe that laser eye surgery is performed exclusively by using non-invasive lasers. In actual fact, physical incisions to the cornea are still made before the laser is used. This means that the cornea must undergo natural healing at the locations were incisions were made. This produces a highly irregular surface at these locations, and these irregularities on the cornea introduce some other aberrations which were previously inexistent. The effect of these so called higher order aberrations may not be as significant as defocus and astigmatism, but they still cause some blurring to the image formed on the retina. The effect of these higher order aberrations is particularly noticeable at night when the lower light intensity causes the pupils to dilate, and hence light passes through a larger area of the irregular cornea.

(2) The physical incisions as well as the laser ablation of the cornea results in a thinner cornea after the surgery. I have deliberately omitted a description of the LASIK surgery since it might adversely affect sensitive readers The final
outcome is, however, that the cornea is thinnest at the centre of the pupil and this can be dangerous in some cases.

(3) Another major concern of corrective eye surgery is that in a substantial number of cases, full correction is not achieved. People having 6D of myopia, say, might have a correction of only 4D which still leaves them with 2D of myopia - hence they would still require spectacles or contact lenses. People who spend so much money on corrective surgeries would not be very pleased of the fact that they would still require spectacles or lenses! The reason for this partial correction is that the processes of predicting the required cornea shape and producing that shape are restricted by current technology. Hence for most of the eyes which need correction, it is very difficult to obtain perfect correction of the eyesight. This is clearly a major drawback to LASIK and other corrective surgery techniques.

(4) One other significant point to mention is that the aberrations of the eye are not constant but they change with time. Thus, the effects of a successful laser surgery (assuming that you can have a successful laser surgery) will only last for a few years. With spectacles the problem is easily resolvable - buy a new pair of specs - but repeating the eye surgery every decade, say, somehow does not sound so easy!

At the end of the day everyone has to make his or her own decision on whether to take the risk or not. What I can say is that I would never consider having laser corrective surgery, in any of its current forms, performed on my eyes even though my eyesight is not that good. I definitely prefer specs sitting on my nose then the hazards and inconveniences of eye corrective surgery. If you are considering LASIK, beware.

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