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IOL optics
Anatomy & Optics
Key Points
- •Axial length is the most important measurement - 1 mm error → ~2.5 D error in IOL power; optical biometry (IOLMaster/Lenstar) is the gold standard
- •Barrett Universal II is currently the most accurate formula across all axial lengths; Hoffer Q is preferred for short eyes, SRK/T for long eyes
- •Post-LASIK eyes cause the most refractive surprises - standard keratometry overestimates power → hypermetropic surprise; use Barrett True-K or clinical history method
- •A-constant optimisation (personalising the A-constant from surgical outcomes) is the single most effective step to improve refractive accuracy
- •Toric IOL rotation: every 1° rotation → 3.3% loss of cylinder effect; at 30° rotation the cylinder effect is completely lost
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