laser corrective eye surgery
I am the holder of a Class-1 Medical Certificate which specifies a requirement
for vision correction due to Short Sightedness. Can you please advise me of the
benefits and/or problems which could be expected from Laser Corrective Surgery?
The excimer laser was introduced in 1983 and, since then, has been used to
perform laser corrective surgery on the eyes of myopic (short sighted)
individuals. The procedure involves using the laser to burn away (ablate) a thin
layer from the 4 - 7 mm diameter central area at the front of the eye (cornea).
This acts to change the shape of the front of the eye and, if all goes according
to plan, correct the visual problem. This procedure is usually called
Photo-Refractive Keratectomy - PRK.
Being a relatively new procedure the problems and complications of PRK surgery
are not, yet, terribly well documented as are currently under intensive study.
The information provided here is based on a recently published review article as
well as information provided by USAF colleagues.
Astigmatism if the ablation zone is placed off centre.
If the area of ablation doesn't end up exactly as planned an alteration of the
eye's visual axis (astigmatism) might result.
At night if the pupil dilates beyond the zone of ablation (the central 4 - 7 mm
of the eye) then optical aberrations may ensue causing blur, halos, and
decreased night vision.
The deeper the laser ablation the thinner the remaining cornea. This may
compromise the biomechanical structure and reduce corneal stability. Future
studies may clarify this.
Corneal healing, scarring, and regression. After the PRK procedure is
performed a period of healing occurs. This healing often leads to further
changes in the function of the eye - usually towards the original problem. Some
surgeons try to overcorrect when performing PRK to allow for this 'regression'.
The deeper the laser ablation (i.e. the worse the myopia to start with) the
greater the scarring or haze, and the greater the degree of regression of
'Haze' and 'Halos' in the vision can also occur because of scarring of the front
of the eye. One study reported that 10% of people who had had their first eye
treated using PRK (the usual practice is to operate on the eyes separately -
just in case) declined having their other eye treated a year later because of
persistent haze and/or halos.
A deep PRK ablation (cases of more severe myopia) may result in physical
weakening of the structure of the eye. This might make other physical injuries
(i.e. a piece of metal in your eye) more likely to cause more serious damage.
This potential problem has currently not been substantiated and remains
While PRK appears to be effective, safe, and satisfactory for many of the
general population some of its problems might cause a pilot second thoughts.
In one group studied 78% experienced disturbances in night vision. A pilot might
not find this risk acceptable given the possible high workload and visual
demands of some night flying.
A small, but not insignificant, number of PRK subjects end up with worse vision
than before the procedure.
It is also theoretically possible for PRK to interfere with your visual depth
perception. This could result if each eye ends up with a different degree of
correction - due to the original amount of ablation or the subsequent scarring /
PRK offers the general population some advantages over other myopia correction
options. It does, however, also have a number of side effects that might be of
unacceptable risk to a pilot.
Me? I probably wouldn't consider PRK at the moment. I'd want to wait another 5
years or so until we had a much better understanding of this, relatively new,