Corneal topography using Placido disc technology measures which surface of the cornea?
- A Posterior corneal surface
- B Anterior corneal surface only ✓
- C Both anterior and posterior corneal surfaces
- D Corneal epithelial thickness map
Correct answer: B. Anterior corneal surface only
Explanation
Placido disc-based corneal topographers analyse reflected concentric ring images from the anterior corneal surface only, mapping anterior curvature. They cannot assess the posterior surface. Scheimpflug cameras (Pentacam, Galilei) and OCT-based systems measure both anterior and posterior surfaces and provide pachymetry maps. The distinction is critical in pre-LASIK screening where posterior surface elevation on Scheimpflug imaging may reveal keratoconus not visible on Placido topography.
Reference: Khurana Comprehensive Ophthalmology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.