A 32-year-old underwent uncomplicated myopic LASIK five years ago and now has a dense cataract. If standard keratometry values measured before cataract surgery are entered into a modern IOL formula without correction, the expected refractive outcome will be:

• A Myopic surprise, because standard keratometry underestimates corneal power after myopic ablation
• B Accurate, provided axial length is measured by optical biometry
• C Hyperopic surprise, because standard keratometry overestimates corneal power after myopic ablation ✓
• D Unpredictable astigmatism unrelated to the keratometry error

Explanation

After myopic laser ablation, standard keratometry measures the steeper midperipheral cornea rather than the flattened central zone, so it overestimates the effective corneal power. An overestimated K leads the formula to select too weak an IOL, producing a hyperopic refractive surprise. Corrected approaches include the Haigis-L and Barrett True-K formulas, the clinical history method using prior refractions, and direct measurement of total corneal power by Scheimpflug tomography.

Reference: Yanoff and Duker Ophthalmology, 5th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.