Accommodating Intraocular Lenses
Accommodating IOLs attempt to restore a significant amount of true accommodation to patients with surgically induced pseudophakia. Accommodating IOLs were designed following the observation that some patients who received silicone-plate IOLs reported better near vision than that expected from their refractive result. Investigations revealed that, during ciliary muscle contraction, forward displacement of the IOL led to an increase in the IOL’s effective power and thus an improvement in near vision. However, some studies have questioned the amplitude of true accommodation that can be expected solely on the basis of anterior displacement of the IOL optic. Other factors, such as pupil size, withthe-rule astigmatism, and mild myopia, may also contribute to unaided near visual acuity and increased depth of focus.
Some IOLs that use this accommodative approach are modified silicone plate–haptic lenses (Fig 9-5). These lenses may allow anterior movement of the lens during accommodation. Another possibility is that ciliary body contraction causes a steepening of the anterior optic surface, allowing for better near vision. Although the exact cause of the movement is unclear, it appears to be a combination of posterior chamber pressure on the back surface of the IOL and ciliary body pressure on the IOL that vaults the optic forward. The anterior displacement is postulated to result in an effective increase in optical power and near vision.
Figure 9-5 Example of an intraocular lens with a flexible hinge in the haptic at the proximal end and a polyamide footplate at the distal end. The footplate functions to maximize contact with the capsule and ciliary body, and the hinge transfers the horizontal force into an anteroposterior movement of the optic.
(Courtesy of Eyeonics, acquired by Bausch + Lomb.)
Findl O, Kiss B, Petternel V, et al. Intraocular lens movement caused by ciliary muscle contraction. J Cataract Refract Surg. 2003;29(4):669–676.
Langenbucher A, Huber S, Nguyen NX, Seitz B, Gusek-Schneider GC, Küchle M. Measurement of accommodation after implantation of an accommodating posterior chamber intraocular lens. J Cataract Refract Surg. 2003;29(4):677–685.
Excerpted from BCSC 2020-2021 series: Section 13 - Refractive Surgery. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.