Light Adjustable Lens (LAL®) Technology
Intraocular lenses (IOLs) have been used in cataract surgery for more than 60 years. Standard monofocal IOLs allow some patients to have good distance vision, but the majority of patients are left dependent on glasses for optimal distance and reading vision.
There are many types of replacement lenses available, but one of the critical drawbacks to even modern lens design is the difficulty in achieving optimal visual outcomes for patients. Despite careful measurements of the eye prior to surgery, several factors including preexisting corneal astigmatism and unpredictable wound healing can result in suboptimal patient vision after the lens implantation. This can require the patient to wear glasses or have subsequent surgery, such as LASIK, to see well at both distance and for reading.
The LAL is similar in many respects to standard monofocal IOLs, which cataract surgeons all over the world are very familiar with. As such, it can be implanted in the eye by surgeons using their customary surgical technique.
However, what makes the LAL different are special biocompatible materials called macromers that are incorporated into the makeup of the LAL; these materials are sensitive to ultraviolet light of a certain wavelength, and when irradiated by such light, the macromers undergo a chemical change known as photopolymerization. This subsequently leads to a predictable change in the shape of the LAL’s surface and hence, the power of the lens.
Mechanism of Action
Light adjustability of the lens is based on the principles of photochemistry and diffusion, whereby components incorporated in the silicone lens matrix are photopolymerized upon exposure to ultraviolet light. The mechanism of action of the LAL technology is depicted graphically in the figure below.
Application of ultraviolet light onto the LAL causes photopolymerization of macromers in the irradiated region of the lens to occur, removing macromers from this region. This will result in disequilibrium within the lens because macromers are present in the non-irradiated areas, but are missing from the irradiated region. To reestablish equilibrium across the lens, macromers from the non-irradiated area will diffuse into the photopolymerized portion of the lens, producing a swelling that changes the lens curvature.