IOL

An intraocular lens (IOL) is an artificial lens implanted in the eye to replace the eye's natural crystalline lens, typically after removal of a cataract or during refractive lens exchange. IOLs are placed in the posterior chamber, most often within the capsular bag. They aim to restore focusing power and, depending on design, reduce dependence on spectacles.

IOLs come in various designs and materials, including monofocal, multifocal, toric, accommodating, and extended depth of focus. Materials include polymethyl methacrylate (PMMA), silicone, and acrylics (hydrophobic or hydrophilic). Common configurations are one-piece and three-piece designs, with different haptic geometries for stable positioning in the capsular bag. Toric IOLs correct corneal astigmatism; multifocal and extended depth of focus IOLs provide a range of focus; accommodating IOLs attempt to change power with ocular accommodation.

Most IOLs are implanted during cataract surgery using phacoemulsification with a small corneal incision, enabling injection of a foldable IOL into the capsular bag. Postoperative outcomes are generally favorable, with improved best-corrected and uncorrected vision and reduced dependence on spectacles for many patients, though refractive results depend on ocular biometry and IOL power calculation.

Complications are rare but include posterior capsule opacification, IOL dislocation, glare or halos with multifocal designs, infection, inflammation, cystoid macular edema, and secondary glaucoma. Long-term biocompatibility and accuracy of power calculations have improved with advances in materials and design.

The concept originated with Sir Harold Ridley, who proposed intraocular lenses in 1949 and contributed to their clinical development. Modern IOLs have evolved into a standard of care in cataract surgery and refractive lens exchange.