What is the key optical principle distinguishing diffractive multifocal IOLs from refractive multifocal IOLs?

• A Diffractive IOLs use concentric ring zones that diffract light to multiple foci, creating near and distance correction simultaneously, independent of pupil size ✓
• B Refractive IOLs use diffractive grooves to separate wavelengths of light
• C Diffractive IOLs function only in photopic conditions when the pupil is small
• D Refractive multifocal IOLs use alternating zones of different curvature independent of the optic centre

Explanation

Diffractive multifocal IOLs use concentric diffractive rings (step-heights) etched on the posterior optic surface to split incoming light into two or more focal points (distance and near) simultaneously using the principle of light diffraction. This splitting is independent of pupil size, ensuring near and distance vision across varying light conditions. Refractive multifocal IOLs use concentric zones of different refractive powers (centre-near or centre-distance designs) that are pupil-size dependent. Diffractive designs account for most modern presbyopia-correcting IOLs (e.g., AcrySof IQ ReSTOR).

Reference: Khurana Comprehensive Ophthalmology, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.