Laser refractive surgery is one of the best documented procedures in the world. Its risks are real, known, and for the most part manageable. Understanding them is the condition for an informed decision.
This is the most common side effect after Femto-LASIK. Creating the flap severs superficial corneal nerves, temporarily reducing corneal sensitivity and reflex tear production. Postoperative dry eye affects 20 to 55% of patients depending on the studies, but in the vast majority of cases is transient and resolves in three to six months with appropriate treatment.[1]
PRK, which does not create a flap, affects corneal innervation less. It is preferred in case of pre-existing dryness.
Almost universal in the first postoperative weeks, they correspond to light diffraction at the transition zone between treated and untreated cornea. They diminish progressively as the cornea heals and the brain adapts. At three months, they are residual or absent for the majority of patients.[2]
Their persistence beyond six months is possible, particularly for larger corrections or wide pupils in scotopic conditions.
In the first weeks, vision can vary with the time of day, fatigue or hydration. It is a normal phase of corneal healing. It generally stabilises in one to three months for Femto-LASIK, in three to six months for PRK.
A slight loss of the correction achieved can occur in the months or years following surgery, particularly for high myopia. It is generally minimal and can be treated with a laser enhancement if needed.[3]
This is the most feared complication. It corresponds to a progressive thinning and deformation of the cornea after laser ablation, similar to keratoconus. It occurs mainly in patients with pre-existing corneal fragility undetected during the exam, or insufficient residual thickness.[4]
Its frequency is estimated at 0.04 to 0.6% of cases depending on the populations studied. It is largely predictable and avoidable with a rigorous topographic exam. This is the main reason why corneal topography is the most important test of the preoperative exam.
Flap folds, traumatic displacement, irregular interface. These complications are rare since the introduction of the femtosecond laser (less than 1% in total) and in the majority of cases treatable.[5]
Exceptional thanks to systematic antibiotic protocols. Its frequency is estimated at less than 0.02% of cases in centres respecting sterilisation and postoperative prescription standards.
A slight superficial opacification of the cornea can occur after PRK, especially for larger corrections. The application of mitomycin C at the end of the procedure has significantly reduced this risk. It remains possible in cases of overcorrection or atypical healing.[6]
The vast majority of serious complications of laser surgery are avoidable through a rigorous exam. Corneal topography detects pre-existing fragility. Pachymetry evaluates the available tissue reserve. Tear film assessment identifies dryness to be treated before surgery.
A thoroughly performed complete exam rules out the vast majority of at-risk profiles before surgery is even considered. That is its main role.
Satisfaction rateIn studies on selected populations, the satisfaction rate after laser refractive surgery exceeds 95%. It depends on rigorous candidate selection and realistic expectations.[7]
References
International literature is clear: laser refractive surgery is one of the best documented surgical procedures in the world. The rate of severe complications (irreversible loss of lines of acuity) is below 0.1% in published series on properly selected populations.
The vast majority of reported side effects — halos, night glare, transient dryness — are moderate and regress within a few weeks to a few months. They occur more frequently in patients operated outside strict eligibility criteria, which underlines the importance of a rigorous preoperative exam.
Almost all severe complications of laser surgery occur in patients who should not have been operated on: cornea too thin, early keratoconus undetected, unstable correction. The preoperative exam's role is precisely to rule out these profiles before any surgical decision.
A rigorous exam, including corneal topography, pachymetry, aberrometry and tear film analysis, is the main protection against surgical risk. It also helps tailor the technique (Femto-LASIK vs PRK) and laser parameters to each individual profile.