Proof Of Concept With A New Nitinol-Based Thermomechanically Adjustable Intraocular Lens.

Unintended residual refractive error after cataract surgery or refractive lens exchange form the last barrier to improve outcomes of those surgeries. We want to report in vitro and in vivo tests with a novel nitinol-based thermomechanical mechanism on an acrylic one-piece IOL showing stepwise adjustability of the IOL position in a water chamber for theta axis (toric) and zeta axis (spherical) directions, and in vivo in a rabbit for the toric movement.  

Laboratories of Eye Med Technologies, Israel.

A nitinol-based ratchet and lever actuator mechanism for toric movement and a mechanism of rings with actuators for anterior posterior movement were manufactured and attached to an acrylic IOL. The haptics serve as the cradle and the optic lies within the ring-mechanism. In a water chamber the mechanism activated by a green continuous (Argon) laser to produce a toric movement of the IOL. One week after implantation in a rabbit the mechanism was successfully activated in vivo. The anterior posterior mechanism (the spherical component) was activated and tested in a water chamber. Foldability and implantability of the last prototype was tested by folding, loading of a cartridge and injection of the IOL into a petri dish.

The toric mechanism was successfully activated in vitro and in vivo, producing a counterclockwise and clockwise movement of the optic versus the cradle haptics of 1 degree per movement. Actuation resulted in lifting of the lever mechanism and movement of the optic of the lens along the cogwheel mechanism in preset steps both in vitro and in vivo. The spherical component mechanism was tested in the water-chamber resulting in anterior posterior and posterior anterior movements of the rings, with a complete reset to the starting point in each case. Foldability was successfully demonstrated in a 3 mm off the shelf injector into a petri dish. 

The proof of concept for a novel thermomechanical adjustable IOL was delivered. By means of argon laser activation of the nitinol-based mechanism, movement in the optic was induced, and the IOL optic moved in clockwise and counterclockwise directions, in measured steps for the toric components and the anterior posterior and vice versa movement in the spherical mechanism. The prototypes were shown to be foldable through existing IOL cartridges and injectors. More study is needed for development of this prototype into a mature IOL technology that will allow intraocular adjustment of the effective lens position after cataract surgery in case of unintended residual refractive error after lens implantation.