Corneal topography using Placido disc-based keratometry in a patient who wears rigid gas-permeable contact lenses for keratoconus shows a central flat island surrounded by steepening. The most likely interpretation is:
- A Classical inferior pellucid marginal degeneration pattern
- B Contact lens-induced corneal warpage causing central flattening artefact ✓
- C Post-LASIK central island formation
- D Keratoconus progression with apical scarring
Correct answer: B. Contact lens-induced corneal warpage causing central flattening artefact
Explanation
Long-term rigid contact lens wear induces corneal warpage: the flat central zone reflects moulding by the back surface of the RGP lens, while the peripheral steepening is the residual ectatic cornea. Patients should discontinue RGP lenses (minimum 2–4 weeks for soft, 4–8 weeks for RGP) before reliable topography. Post-LASIK central islands are a distinct pattern; pellucid marginal degeneration shows inferior peripheral steepening with central flattening in a 'butterfly' pattern.
Reference: Khurana Comprehensive Ophthalmology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.