A 45-year-old patient undergoes LASIK refractive surgery. Three months later she develops a slowly progressive central corneal ectasia with decreasing best-corrected visual acuity. Corneal topography shows inferior steepening. The mechanism of post-LASIK ectasia is:

• A Infection of the LASIK flap interface with atypical Mycobacteria
• B Haze from subepithelial fibrosis in the ablation zone
• C Inadequate residual stromal bed thickness and pre-existing forme fruste keratoconus leading to biomechanical failure of the corneal stroma ✓
• D Diffuse lamellar keratitis (DLK) causing stromal melting

Explanation

Post-LASIK ectasia occurs when the residual stromal bed is too thin (guidelines recommend ≥250 µm) or when a pre-existing subclinical keratoconus (forme fruste) was undetected preoperatively. The laser ablation removes stromal collagen and weakens the corneal biomechanics; combined with insufficient stromal thickness, the posterior cornea bulges forward under normal intraocular pressure. Risk factors include high myopia correction (deep ablation), thin preoperative cornea, and any asymmetry or inferior steepening on preoperative topography. Treatment options include corneal cross-linking (CXL) to halt progression and intracorneal ring segments or keratoplasty.

Reference: Khurana Comprehensive Ophthalmology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.