Monofocal Intraocular Lenses

Excerpt

The human crystalline lens accounts for +15 to +20 (approximately 17) diopters of the refractive power of the eye. The cornea contributes another 43 diopters. Cataract surgery involves the removal of the opacified crystalline lens, making the eye aphakic. Before the invention of intraocular lenses (IOLs) by Sir Harold Ridley to correct aphakia, spectacle correction was the norm.

Aphakic spectacles were unsightly and heavy. They cause spherical aberrations and distortion in vision. Removal of the entire crystalline lens by intracapsular cataract extraction (ICCE) necessitated implantation of the intraocular lens in the anterior chamber. This led to the invention of various designs of lenses after the original Ridley lens.

Peter Choyce and Sir Harold Ridley formed the International Intraocular implant club in 1966. This led to the gradual acceptance of intraocular lenses. Intracapsular cataract extraction with anterior chamber IOL was gradually replaced by extracapsular cataract surgery with posterior chamber IOLs. However, the original Ridley lens was implanted after extracapsular cataract surgery, which involves leaving the posterior capsule of the lens behind.

Charles Kelman revolutionized cataract surgery by inventing the technique of phacoemulsification. Howard Gimbel invented the technique of capsulorhexis, due to which intraocular lenses could be implanted in the bag. Femtosecond laser technology further improved the precision with which surgery could be performed.

Intraocular lenses have transitioned from anterior chamber IOLs to posterior chamber IOLs, which have undergone further modification from rigid polymethylmethacrylate (PMMA) lenses to silicone and acrylic lenses. Lens materials and designs have undergone many improvements. Hydrophilic and hydrophobic lens materials are both in vogue. Open looped, closed-loop, plate haptic, and square-edged designs are currently being implanted, each modification attempting to decrease the incidence of complications, including posterior capsular opacification. Monofocal intraocular lenses to correct distance vision are the most commonly implanted intraocular lenses.