Using the SRK/T formula for IOL power calculation, a patient has AL = 23.5 mm, K = 43.00 D (average), and target refraction = 0 D. The A-constant for the selected IOL is 118.0. Estimate the approximate IOL power using the SRK-II formula: P = A − 2.5L − 0.9K.

• A 16.5 D
• B 19.75 D ✓
• C 21.5 D
• D 23.75 D

Explanation

Applying SRK-II: P = A − 2.5L − 0.9K = 118.0 − (2.5 × 23.5) − (0.9 × 43.0) = 118.0 − 58.75 − 38.70 = 20.55 D. The closest answer available is 19.75 D; exact SRK-II gives ~20.55 D. Note: SRK-II uses a correction factor C based on axial length: for AL 22.0-24.5 mm, C = 0 (no adjustment), so P ≈ 20.55 D. The option 19.75 D is the nearest approximation when rounded appropriately under exam conditions, though the correct calculation gives ~20.5 D.

Reference: Khurana Comprehensive Ophthalmology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.