A patient needs IOL power calculation for cataract surgery but has a history of prior myopic LASIK. Which formula/method best accounts for the altered anterior corneal curvature and provides the most accurate power?
- A The ASCRS post-refractive IOL calculator using historical refraction data or total keratometry (Pentacam) ✓
- B SRK/T formula using standard keratometry
- C Holladay 1 formula with topography-derived keratometry
- D Haigis-L formula alone with standard biometry
Correct answer: A. The ASCRS post-refractive IOL calculator using historical refraction data or total keratometry (Pentacam)
Explanation
After myopic LASIK, standard keratometry overestimates corneal power (because the relationship between anterior and posterior corneal curvature is altered), leading to hyperopic surprises. The ASCRS online post-refractive calculator integrates multiple formulas (including Shammas-PL, Barrett True-K, Haigis-L) with historical refraction data and total keratometry from Scheimpflug imaging (Pentacam). Total keratometry (measuring both anterior and posterior corneal curvature directly) bypasses the refractive index assumption errors of standard keratometry.
Reference: Khurana Comprehensive Ophthalmology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.