For ophthalmologists looking for new lens options, accommodative IOLs continue to evolve in promising directions.
This article was reviewed by Stephen D. McLeod, MD
Change is a constant and with change in accommodating IOLs comes potential improvements in vision for presbyopic patients.
True accommodation means that the optic must instantaneously change power from distance to near and back. The most familiar strategy to accomplish this is a change in optic position, but other strategies to produce accommodation are changes in the lens curvature and in the refractive index or optic power, according to Stephen D. McLeod, MD, professor and chairman of ophthalmology, University of California San Francisco.
Regarding the lens position, surgeons are familiar with both the CrystaLens (Bausch + Lomb) and the Kellan Tetraflex (Lenstec). The Tek-Clear Accommodative Lens (Tekia), a lens with a 360-degree haptic structure and a single optic vault, is a slightly newer IOL than the previous two.
Lenses that depend on movement to change accommodation are limited in their ability to do so.
Dr. McLeod pointed out that an issue with all of these devices are limited by the typical optic powers required by patients who are emmetropic or low and high myopes.
“When dealing with an optic that moves forward, the degree of that movement is not great, often much less than 1 mm, and for most lens powers implanted, the observed degree of movement produces minimal accommodative change proportional to the power of the lens that is moving forward,” he said.
According to Dr. McLeod, the accommodative IOL models that change lens curvature can more efficiently effect the desired focus shift.
“For just about any IOL regardless of power, the amount of accommodative change that you get from the entire lens moving forward a given distance is an order of magnitude less than the accommodative change you get from an increase in curvature that shallows the anterior chamber by the equivalent amount,” he said.
The FluidVision IOL (PowerVision, now Alcon), a lens curvature IOL, is one of the older designs with peripheral reservoirs and distensible central optics. When the fluid moves from the reservoir to the center, the curvature changes.
The Opira accommodating IOL (ForSight Labs) is a sulcus-based device for which the haptics are fixed in the capsulorhexis. “The anterior optic accepts the fluid from the reservoir leading to the change in curvature,” Dr. McLeod said.
The Juvene IOL (LensGen) is based on the same principle as the Opira IOL. “This lens has two compartments. The anterior optic is the one that accepts the fluid from the reservoir, and the posterior element remains available for refining the focus power of the eye or for a toric correction,” he pointed out.