Does lasik have any long term problems?
1. Corneal Ectasia:
This means a bulging outwards of the central cornea which has been thinned too much by myopic Lasik. (it is not a problem with hyperopes). The international standard is to leave 250 microns behind to maintain corneal strength (see Lasik contraindications). This problem is obviously more likely with the higher treatments and most cases have occurred with myopia over -8 Dioptres and again it is more likely with an unwise re-treatment. I was at the recent meeting of the European Society of Cataract and Refractive Surgery in Cannes in January 2001 where there was a symposium on just this problem. One "belt and braces" suggestion which I now follow is to do intra-operative corneal pachymetry (using a small ultrasound probe to actually measure what corneal thickness there is under the flap) in higher myopes before going ahead with the laser ablation. This is because, although the microkeratome may be designed to cut a flap of 160 microns, it may actually cut a flap somewhat thinner or thicker in a particular patient. Also, the laser ablation may take off a bit more or less than planned as no one yet knows how to measure what the laser is taking off in 'real time' (while the laser is firing).
The effect of corneal ectasia is that the cornea becomes steeper and hence the eye becomes short sighted again. This may be corrected by glasses, but in more severe cases, a gas permeable contact lens may be needed or even a corneal transplant (corneal graft). Corneal ectasia is similar to the corneal disease of Keratoconus or 'conical cornea'. Despite following all the guidelines, I personally have had one patient who had a moderate corneal ectasia who needs a gas permeable lens and since then I have been more cautious and conservative.
Most cases of corneal ectasia will occur within 6 months after surgery, but we cannot rule out milder cases taking years to develop.
Corneal ectasia is not really a problem with longsight as much less tissue is taken off and even this is in mostly in the mid-periphery rather than the centre.
2. Flap Stability:
The edges of the flap are sealed by epithelium by one day after surgery and over the next few months the flap itself adheres more and more to the underlying cornea. We do re-treatments at about 3 months, when the flap can be physically lifted, rather like lifting off the sticky flap on an envelope. Beyond 6 months, this becomes much harder, or even impossible, to do, especially in young people. In some patients there have been reports that the flap can be lifted for re-treatment up to 2 years after surgery, although I suspect that this is unusual. It would take a hard oblique blow directly onto the flap to actually move it and actual reports of this happening seem to be very rare. One case was with the airbag of a car accidentally going off, another was a soldier running through some bushes and being caught in the eye by a thorn.
3. Dry Eyes:
Long term dry eye problems can occasionally occur, especially in older people with an initial poor tear film. This can be usually cured by putting in silicone plugs in the lower punctae of the eyelids; rather like putting a plug in the plughole of a bath - what tears there are stay around for longer before evaporating. These plugs retail at about £25 each.