Dual-optic IOL effective answer to presbyopia

An important feature of the Synchrony IOL is that it seems to provide more accommodation than single-optic design accommodative IOLs as well as good near, intermediate, and distance vision, according to Ivan Ossma-Gomez, MD.

To date, more than 250 eyes have had the lens implanted at eight centers in Mexico, Colombia, Germany, and Canada. The manufacturer recently received approval from the FDA to begin implanting the IOL in the United States late last year, and the clinical trials started at the end of the fourth quarter of 2005. A new feature of this lens is that the manufacturer has developed an injector system to replace the forceps used to implant the lens when it initially became available. The lens is provided pre-loaded in the injector system that allows insertion through a 3.6- to 3.8-mm clear-corneal incision.

The Synchrony IOL has a single-piece, silicone, dual-optic design. The 5.5-mm anterior optic is highly powered and is connected to a 6.0-mm negative-power posterior optic by haptics that have a spring-like action. The IOL has a high-power moving lens and a larger range of accommodation than a single-optic one. The IOL provides consistent accommodation for all patients, he explained. Dr. Ossma-Gomez is assistant professor of ophthalmology, Department of Ophthalmology, Fundacion Oftalmologica de Santander, Bucaramanga, Colombia.

The design of the lens is such that the front optic moves; it has a high plus of +32.0 D. The rear optic is patient dependent and varies with each patient depending on ciliary muscle movement. The net power of the IOL is individualized, with a theoretical accommodation of 3.3 D, with 1.5 mm of anterior lens movement, Dr. Ossma-Gomez explained.

How it works

The IOL works in the following manner, according to the manufacturer.

The mechanism of action of this lens is based on a lens structure formed by two optics linked by a spring system that, when resting, produces an outward force separating the axis of the optics. When implanted within the capsular bag, bag tension compresses the optics reducing the interoptic separation.

The resting ciliary body maintains zonular tension that is transmitted to the bag, producing outward circumferential movement of the equator. Axial shortening of the capsular bag and compression of the lens results in the storage of strain energy in the connecting arms.

Stoppers are incorporated to control minimum separation of the lenses and maintain a very small space between the two lenses, thus setting the resting distance refraction at emmetropia. With accommodative effort, the zonules relax, releasing the tension on the capsular bag, thus allowing release of the strain energy stored in the interoptic articulations and anterior displacement of the anterior optic.

The posterior optic has a pair of stabilizers that reduces the tendency for posterior axial excursion and maintains stability and centration within the capsular bag during the accommodative process.

Results

The visual results reported thus far are good.

In 23 eyes with the lens implanted by Dr. Ossma-Gomez that were followed for 2 years, 83% of the eyes had 20/40 or better uncorrected distance visual acuity (VA) and 100% had distance-corrected VA of 20/40 or better. Regarding intermediate vision, 92% had 20/40 or better uncorrected VA and 96% had distance-corrected VA of 20/40 or better. And regarding near VA, 100% had both uncorrected VA of 20/40 or better and distance-corrected VA or 20/40 or better.