Corneal topography of a 24-year-old contact lens wearer shows inferior steepening with a best-fit sphere irregularity and a scissoring reflex on retinoscopy. The MOST likely diagnosis is:
- A Pellucid marginal degeneration
- B Keratoconus ✓
- C Contact lens-induced corneal warpage
- D Posterior keratoconus
Correct answer: B. Keratoconus
Explanation
Inferior corneal steepening on Placido-based topography (with a crab-claw or skewed radial axis pattern), combined with a scissoring reflex on retinoscopy and the patient's age, is classic for keratoconus. Pellucid marginal degeneration causes inferior thinning with steepening superior to the thinning and a characteristic 'butterfly' pattern. Contact lens warpage can simulate topographic irregularity but resolves on cessation. Posterior keratoconus is a localised posterior surface change without the anterior progression.
Reference: Khurana Comprehensive Ophthalmology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.