Why one in five people who want LASIK should not have it

Why screening decides the outcome

The laser is not the variable. Modern excimer platforms are all excellent. What separates a good result from a bad one is whether the right patient was put under it. Screening is where refractive surgery is won or lost, and it happens before the laser is switched on.

The cornea has to be thick enough

LASIK removes tissue from the stroma. Remove too much and the cornea weakens structurally, which can lead to ectasia — a progressive thinning that is the single worst complication in refractive surgery. We measure corneal thickness with pachymetry and map its shape with topography. If the residual bed under the flap would be under 250 microns, we do not do LASIK. We offer PRK or ICL instead, or we do nothing.

Keratoconus hides in plain sight

Keratoconus is a progressive thinning disorder where the cornea becomes cone-shaped. It is more common than most people assume, and in its early stages it can look almost normal on a basic exam. Operating on an undetected keratoconic eye is one of the few ways to do real harm. Topographic screening catches it, and we screen every single patient.

A prescription that will not sit still

If your prescription is still changing, the surgery will fix today's number and nothing else. We want stability — generally no more than 0.50 dioptres of change over two years. A young patient with a moving prescription is a patient we would rather monitor than operate on.

Dry eye is not a small thing

Refractive surgery temporarily reduces corneal sensation, which reduces tear production. In a patient who already has significant dry eye, that can turn a manageable annoyance into a persistent problem. We measure tear film before we consider operating, and we treat dry eye first where it is present.

The honest summary

Roughly one in five people who come to us wanting LASIK leave without it. Some are better served by PRK or an implantable lens. Some need their dry eye treated first. Some should simply stay in glasses, and we tell them so plainly, because a pair of glasses is a far better outcome than a damaged cornea.