During pre-operative biometry for cataract surgery, the SRK/T formula is LEAST accurate for which axial length range?

• A Axial length 21–24 mm (normal eyes)
• B Axial length < 22 mm (short eyes)
• C Axial length > 26 mm (high myopia)
• D Eyes after previous LASIK ✓

Explanation

The SRK/T formula, like all thin-lens vergence formulas, is least accurate in eyes that have undergone prior corneal refractive surgery (LASIK, PRK, RK) because these procedures alter the relationship between anterior corneal curvature and true corneal power, invalidating standard keratometry-based assumptions. For post-refractive eyes, special methods (e.g., Haigis-L, Shammas, or Barrett True-K) are required. The SRK/T performs acceptably for short and long eyes, though third-generation formulas like Haigis or Barrett Universal II are preferred for extremes of axial length.

Reference: Khurana Comprehensive Ophthalmology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.