The latest developments in intraocular lenses and technologies.
Intraocular lens technology has improved dramatically during the last twenty years. The majority of implants used today are foldable acrylic one-piece IOLs, most of which have aspheric optics.
Advances in astigmatism-correcting and presbyopia-correcting lenses now offer reduced dependence on glasses to a greater number of patients. However, only a few of these designs are FDA approved. Advanced technology IOLs available outside the United States, as well as novel IOLs in development are discussed below:
Aspheric IOLs: Negative and neutral aspheric lens optics are used to compensate for positive corneal asphericity. Some surgeons recommend measuring corneal asphericity in all patients preoperatively and then choosing the most appropriate neutralizing aspheric IOL.
- My LENTIS (Oculentis): This IOL for patients with highly aberrated corneas is currently being developed. The IOL asphericity will be individually customized for each patient.
Multifocal IOLs: Most multifocal lenses are actually bifocal lenses. However, there are now trifocal lenses that have the advantage of better intermediate vision. Glare and halo is reportedly similar for bifocal and trifocal designs.
- AT LISA tri (Carl Zeiss Meditec): This IOL is a one-piece, acrylic, plate haptic design with a 6.0 mm optic and 11.0 mm overall length. The diffractive design is composed of an intermediate add of 1.66 D and near add of 3.33 D. The trifocal area is devoted to the central 4.34 mm and the bifocal portion occupies the peripheral area from 4.34 to 6.0 mm. The IOL is independent of pupil size for near vision, and it is preloaded in a single use injector that fits through a 1.8 mm incision.
- FineVision (PhysIOL): This is an acrylic, blue blocking IOL having a one-piece design with 4 loop haptics. The optic is 6.15 mm in diameter and the overall length is 10.75 mm. It is an aspheric, diffractive, apodized trifocal lens containing a 3.5 D near add and a 1.75 D intermediate add. It provides excellent intermediate vision and can also be implanted through a 1.8 mm incision.
Multifocal toric IOLs: While the ReSTOR (Alcon) and TECNIS Multifocal (AMO) lenses are FDA approved in the United States, their toric versions are only available outside the U.S. and have demonstrated excellent results. Other multifocal toric lenses that are being used successfully around the globe include:
- M-flex T Multifocal Toric (Rayner): This IOL is a one-piece acrylic lens with a multi-zone refractive aspheric optic containing 4 or 5 annular zones. It is available in two sizes: optic diameter of 5.75 or 6.25 mm and overall length of 12.0 or 12.5 mm, and each of these has a 3 and 4 D add version. The toric power ranges from 1-6 D of cylinder in 0.5 D steps.
- LENTIS Mplus Toric (Oculentis): This IOL is the toric version of the LENTIS Mplus, the refractive multifocal IOL that obtained CE mark in 2009. It is a one-piece plate haptic acrylic lens with a 6.0 mm optic and 11.0 mm overall length. The asymmetric design combines a distance vision zone with a sector-shaped near vision segment having a 3.0 D add on the anterior surface. The aspheric and toric optics are placed on the posterior surface. The lens is pupil independent, and the asymmetric design causes less glare and halo. It also is available in a low add model of 1.50 D for better intermediate vision. The rotational stability is excellent with an average deviation of just 2.78 degrees; however, there are reports of patients being unhappy with the overall vision and the near vision.
Accommodating IOLs:
- Synchrony Vu (AMO): This IOL is a dual-optic accommodating lens with a 5.5 mm high plus power front optic and a 6.0 mm minus power back optic supported by two 9.5 mm length haptics and two stabilizers that extend laterally from the posterior lens with an overall length of 9.8 mm. The lens requires a larger incision of 3.7 mm for insertion.
- FluidVision accommodating IOL (PowerVision): This one-piece IOL consists of fluid reservoir haptics. The capsular forces exerted on the haptics during accommodation cause the fluid to be pumped centrally into the optic resulting in a shape change and increased refractive power (> 5 D on average). When the capsule relaxes for distance vision, the fluid flows back to the haptics, flattening the optic and reducing the lens power.
- AkkoLens: This IOL with a dual optic lens design is placed in the ciliary sulcus. Accommodation exerts pressure on the haptics causing the lens optics to slide, changing their relative position and thus the overall power. This lens is implanted through a 2.8 mm incision.
- NuLens: This IOL is also designed to be positioned in the sulcus. The lens is composed of two rigid plates with a flexible polymer in between. The anterior plate has a central opening through which the flexible material bulges when pressure during accommodation compresses the two rigid plates. The resulting change in curvature increases the power of the lens 30-50 D.
Other IOLs:
- Light Adjustable Lens (Calhoun Vision): This is a unique silicone, three-piece IOL that can be adjusted precisely and non-invasively postoperatively to correct myopic, hyperopic and astigmatic errors of 0.5 to 2 D. Multifocal adjustments also can be performed. The lens consists of photosensitive material which changes with UV exposure to modify the refractive power of the IOL. It is especially useful for patients with previous corneal refractive surgery or difficult corneal measurements. The main disadvantages are the postop treatment time and additional costs of the photosensitizer devices.
- Anti-Dysphotopic IOL (Morcher): This 1-piece foldable IOL was conceived by Dr. Samuel Masket to prevent negative dysphotopsias. In his extensive research, he found that negative dysphotopsias do not occur if the lens optic or optic edge is in front of the anterior capsule. Therefore, he designed this IOL with an annular groove in the edge of the optic off the anterior surface that captures the anterior capsulotomy so the anterior portion of the optic rests in front of the anterior capsule when the haptics are in the bag. Any type of optics (i.e., aspheric, toric, multifocal) can be placed on the lens.
IOL technology is evolving rapidly and there are now more choices we can offer our patients. Hopefully in the near future many of the already existing designs that are in use worldwide will become available in the United States so U.S. surgeons will be able to serve our cataract and lens exchange population more effectively.