Using the SRK/T formula for IOL power calculation, which biometric parameter has the GREATEST influence on the calculated IOL power?
- A Axial length ✓
- B Corneal power (keratometry)
- C Anterior chamber depth
- D Lens thickness
Correct answer: A. Axial length
Explanation
Axial length has the greatest single influence on IOL power calculation; a 1 mm error in axial length measurement causes approximately 2.5–3 D error in the final refraction. Keratometry is the second most important parameter. Anterior chamber depth influences the effective lens position prediction in third-generation formulas but has less absolute impact than axial length. Lens thickness is used in newer-generation formulas (Olsen, Barrett) but has a smaller contribution.
Reference: Khurana Comprehensive Ophthalmology, 7th ed.
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