LASIK or Trans-PRK: what decides the choice?

It is the question I am asked most often in consultation, and the answer sometimes disappoints: the choice is not entirely yours. It follows from measurements, and one of them cannot be negotiated.

What is really at stake

Both techniques remove tissue in the same place, the corneal stroma, with the same excimer laser and the same precision. The difference is how the laser gets there.

LASIK cuts a superficial flap, lifts it, treats the exposed stroma, then lays the flap back. Trans-PRK cuts nothing: the laser itself removes the epithelium, the outermost layer, then treats the tissue directly beneath. The epithelium then grows back, in three to five days.

Everything else (comfort, recovery time, contraindications) follows from this one difference.

The first criterion is thickness

The LASIK flap takes up corneal thickness that is then no longer available for the correction. For the same correction, Trans-PRK uses up less thickness.

The pre-operative assessment measures your cornea to the micron, by pachymetry, and calculates what will remain after treatment. Below a safety threshold, a flap is ruled out: this is not a preference, it is a limit. Trans-PRK then remains possible where LASIK no longer is.

Topography matters just as much. A cornea with an irregular shape, or one that shows signs of weakness, rules out a flap before thickness even comes into it.

The second criterion is your life

Once healed, the flap holds. But in theory it can still be dislodged by a violent blow to the eye. Everyday life is not the issue here. What matters is combat sports, martial arts and certain exposed jobs: police, firefighters, the armed forces.

For these patients, Trans-PRK is preferred, whatever the corneal thickness. Tell me at the assessment: patients do not always think to mention it, and it changes the decision.

What you will go through

This is where the two techniques differ most, and you need to know it before, not after.

After LASIK, recovery is comfortable. Functional vision returns the next day in most cases, and quality of vision in about a week.

After Trans-PRK, the epithelium has to grow back. This regrowth is painful: marked discomfort is common in the first few days, with watering eyes and sensitivity to light. Vision becomes functional in five to seven days, and quality of vision settles over two to six weeks, fluctuating during that time.

Neither is better. One trades a cut for immediate comfort, the other trades a few difficult days for having no flap.

What is not part of the criteria

Price should not come into this decision. Trans-PRK costs less than LASIK on our fee schedule, but it is not a cut-price LASIK: it answers a different corneal situation. Choosing Trans-PRK to save €600 when LASIK is indicated means putting yourself through several days of pain for no benefit.

Nor should how long a technique has been around. You sometimes read that PRK is outdated. It is not: today's Trans-PRK, contact-free and performed entirely by the laser, has little in common with the mechanical PRK of the 1990s.

What remains uncertain

How the two techniques compare for long-term refractive results is still debated in the literature, particularly for night vision quality and stability beyond ten years. Published series show no clear advantage of one over the other when the indication was correctly made, which brings us back, once again, to the quality of the assessment beforehand.

Sources Société Française d'Ophtalmologie (French Society of Ophthalmology), recommendations on corneal refractive surgery.
Wen D. et al., Postoperative efficacy, predictability, safety, and visual quality of laser corneal refractive surgery, American Journal of Ophthalmology.
Haute Autorité de Santé (French National Authority for Health), assessment of refractive surgery techniques.