Cataract removal is the most common surgical procedure in the United States, with nearly 3 million operations performed annually.This number will likely grow, according to National Eye Institute statistics that predict an increase in the number of people in the United States with cataracts from the current level of 20 million to more than 30 million by the year 2020.This estimate is further supported by data from the Framingham Eye Study showing that the prevalence of cataracts increased with age from 4 percent in the 52 to 64 age group, to 50 percent in the 65 to 74 age group, to more than 90 percent in the 75 to 85 age group.
Traditional strategies for these patients have included the following: The newer IOLs that actively accommodate by changing optic position or shape through attempted preservation of ciliary body function have received mixed reviews with regard to the predictability of accommodative range and the longevity of effect; however, the principles involved offer the best opportunity for us to eventually establish a mechanism and outcome that most closely rivals the vision found in youthful emmetropes.
Recent advances in pseudoaccommodative multifocal IOL technology offer a new alternative for those desiring vision at both distance and near.
In March 2005 the Re Stor apodized diffractive IOL from Alcon and the Re Zoom multifocal refractive IOL from Advanced Medical Optics both received FDA approval for capsular bag implantation following cataract surgery. The Re Stor multifocal IOL uses three separate but complementary optical principles (refraction, diffraction and apodization) to achieve satisfactory near and far visual acuity.
The refractive portion of the optic functions like a standard IOL, with the optic periphery dedicated to distance vision and designed to optimize night vision when the pupil dilates under scotopic conditions.
The diffractive portion of the optic consists of 12 concentric rings on the anterior surface of the optic, and it is located within the central circle, which is 3.6 mm in diameter and is designed to provide distance and near vision in moderate to bright light.
Apodization is the radial variation in optical properties that comes from decreasing the height of each concentric ring from the center toward the periphery of the optic surface (from 1.3 to 0.2 µm).
This balances the amount of light energy that is distributed between distance and near as a function of pupil size, which improves the efficiency and effectiveness of the quality of near vision achieved and reduces problems with glare and halos.
Ring location, spacing and variation of height serve within the pupillary aperture to provide a satisfactory near image at approximately 25 to 33 cm. The Re Stor IOL is a foldable IOL designed for placement within the capsular bag at the time of phacoemulsification.
It is injected using the Monarch B or C cartridge through the traditional phacoemulsification incision. The side effect profile of the Re Stor multifocal lens is very similar to that of traditional monofocal IOLs.