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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.
Related: The future: Development of true accommodative IOLs
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.
Related: Striving for perfection: Creating the perfect IOL
“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.
Related: Precise alignment helps surgeons focus on best toric IOL post-op results
Atia Vision has also introduced in 2019 a modular presbyopia correcting IOL with the same basic approach that is comprised of a two-element design. The exception with this IOL is that the posterior element is the accommodative element. “The advantage that this lens offers is that if an adjustment of this optic is needed, it is far more accessible,” he said.
The Lumina IOL (AkkoLens) is an example of the IOLs that use the third option for accommodating IOLs, i.e., change in the refractive index or lens power. This lens is comprised of two elements separated by an interface, a variable curvature cubic optic. “The anterior and posterior cHANGING FOUCsurfaces are displaced relative to each other and this setup changes the power of the intervening space,” Dr. McLeod pointed out.
Dr. McLeod also noted that the advantage of this design is the ability to achieve a “substantial change in the focal length with minimal ciliary body effect.”
Because all of these approaches are mechanical, it raises the question about whether microfluidics or microelectronics can be put to better used to develop accommodative IOLs.
Related: Light-adjustable IOL technology creates novel treatment window
The Sapphire AutoFocus IOL (Elenza) may be one answer to that question. This lens changes focus power without moving and relies on a power cell and a chip embedded in the eye. The device has a remote recharging system in goggles that are worn while the patient sleeps.
“This is a paradigm-shifting lens,” Dr. McLeod said, adding that the sensor for the device can detect change in the pupillary diameter, which triggers the electronics to send a signal to introduce a diffractive pattern on the optics.
The downsides are the large size, heavy weight and complex electronics, but as Dr. McLeod pointed out, it is showing us the direction in which accommodative IOLs are moving.
“There are many technologies under development in the accommodate arena,” Dr. McLeod concluded. “We are hopefully getting to the point at which we can actively change the true focus power of the system with truly accommodative devices in the reasonably near future.”
Read more by Lynda Charters
Stephen D. McLeod, MD
Dr. McLeod has no financial interest in any aspect of this report.