Corneal ectasia is a rare but serious complication after LASIK in which the cornea progressively thins and bulges. Understanding and screening for risk factors is essential to minimise this outcome.
Pre‑existing Corneal Factors
Candidates are carefully assessed for conditions that weaken corneal structure.
- Forme fruste keratoconus, pellucid marginal degeneration, or suspicious topography patterns markedly increase risk.
- Thin baseline corneas and abnormal posterior elevation on tomography are important warning signs.
- Asymmetry between eyes, high corneal curvature, or irregular astigmatism also raise concern.
- A history of chronic eye rubbing, allergy, or atopy is taken seriously as it may reflect biomechanical vulnerability.
Surgical Planning Factors
Safety margins during LASIK planning aim to preserve corneal strength.
- Excessive tissue removal, especially with high myopic corrections, can leave an inadequate residual stromal bed.
- Low residual stromal thickness and high percentage tissue altered (PTA) values are recognised predictors of ectasia.
- Poorly centered or uneven ablations may further destabilise the cornea.
- When risk factors are present, alternatives such as PRK, SMILE, ICL implantation, or no surgery may be recommended instead.
