IOL power calculation is the process of determining the appropriate strength of an intraocular lens to be implanted during cataract or lens surgery. The goal is to achieve a predictable postoperative refractive result.
Inputs
Key parameters include axial length, corneal curvature, anterior chamber depth, and details of the planned lens. These are entered into formulae that model the optical system of the eye.
- Modern formulae account for effective lens position and eye size
- Data usually come from optical or ultrasound biometry and keratometry
- Different targets can be chosen, such as distance, near, or monovision
- Special calculations are needed after previous corneal refractive surgery
Clinical Considerations
Accurate measurements and appropriate formula selection are essential to minimise refractive surprises. Surgeons may personalise constants based on outcomes audits.
- Astigmatism can be addressed with toric lens designs and corresponding calculations
- Discussion with the patient about visual priorities guides target refraction
- In unusual eyes, additional tests or formulae may be used for cross-checking
- Postoperative refraction provides feedback to refine future calculations
