There are a variety of therapeutic approaches to presbyopia correction, all of which have the same goal: to provide patients with spectacle independence. Currently, implantation of multifocal or accommodating IOLs and pseudophakic monovision are popular options; however, these often require an additional refractive procedure after treatment to achieve spectacle independence. Despite advances in biometry and small-incision surgery, the accuracy of IOL calculation remains limited by the variation in the measurements of corneal power, axial length, and anterior chamber depth.
One potential alternative to avoid the need for secondary correction of presbyopia and residual refractive error is the Light Adjustable Lens (LAL; Calhoun Vision, Inc., Pasadena, California). The LAL contains photosensitive macromers that enable a noninvasive postoperative adjustment of refractive power using ultraviolet light (UV light; 365 nanometers). These molecules are precisely distributed throughout the lens; approximately 2 weeks after implantation, they are irradiated with UV light to cause selective polymerization.
Photoreactive macromers dispersed within the cross-linked silicone lens matrix are photopolymerized upon exposure to UV light with a special selected spatial intensity profile. With this irradiation, the photoinitiator initiates polymerization of the macromer photoreactive groups to form an interpenetrating polymer within the lens matrix. Diffusion of the remaining, unirradiated macromers into the irradiated areas induces a change in the lens shape or refractive index, or both, to produce a predictable power change. Every adjustment procedure allows 2.00 D correction of myopia, hyperopia, and astigmatism. It is important that all photoreactive macromers are polymerized, and every patient has to undergo two lock-in procedures (Figure 1).
The LAL may be used during cataract surgery or for refractive lens exchange. Currently for monovision, the correction in the dominant eye is aimed for distance emmetropia; the other eye is aimed for -1.00 D. Two weeks after surgery, we evaluate patient satisfaction. If the patient is doing well with monovision, the correction is locked in. If the patient does not tolerate monovision, he is adjusted for emmetropia.
A 58-year-old patient presented with cataract and a preoperative refraction of -5.00 -0.50 X 170° and -5.25 -0.75 X 18° in the right and left eyes, respectively. The LAL was implanted bilaterally; the right was targeted for emmetropia and the left for -1.00 D. Two weeks after surgery, his far UCVA was 1.0 in the right eye and 0.6 in the left. Near visual acuity was J2. We discussed the possibility of more or less myopia in his left eye; however, he was satisfied with the far and near visual acuities. Therefore, we locked in both eyes.
Monovision, with the use of this technology, provides a good refractive and visual outcome. The LAL may be able to provide a multifocal correction in the future; however, this is not yet possible. In my opinion, use of this technology will be important for the correction of presbyopia because it provides a perfect distance refraction.
Christoph Winkler von Mohrenfels, MD, is a surgeon at Technical University, Munich, Germany. Dr. Winkler von Mohrenfels states that he has no financial interest in the products or companies mentioned. He may be reached at e-mail: email@example.com.