The Light Adjustable Lens โ€“ A Review

European Ophthalmic Review, 2012;6(2):108โ€“11

Abstract:

The purpose of this manuscript is to review the design, development and clinical results of the light adjustable lens (LAL). Evolution in techniques, biometry and intraocular lens (IOL) calculation have improved outcomes and increased expectations after cataract surgery. Nevertheless, Imprecise IOL power determinations, pre-existing and surgical-induced astigmatism, and previous corneal refractive surgery continue to limit post-operative uncorrected vision. The LAL was designed to provide a stable, precise correction of refractive errors with a safe, non-invasive post-operative procedure. The concept behind the LAL is based on photochemistry and diffusion. The adjustment occurs when all non-attached solutes equally distribute themselves throughout the optic after irradiation with ultraviolet light that causes the photosensitive macromers to polymerise in the irradiated region. Clinical results have been positive, with the largest series (122 eyes) showing 97 % of patients within 0.25 D of attempted spherical equivalent and 100 % uncorrected vision 20/25 or better. In conclusion, the LAL has demonstrated to be a safe, accurate and reliable method of post-operative, non-surgical correction of residual sphero-cylindrical refractive error.
Keywords: Light adjustable lens, cataract surgery, intraocular lens, intraocular lens calculation
Disclosure: The author has no conflicts of interest to declare.
Received: November 28, 2011 Accepted January 06, 2012 Citation European Ophthalmic Review, 2012;6(2):108โ€“11
Correspondence: Alejandro Lichtinger, Toronto Western Hospital, University of Toronto 399 Bathurst street, East Wing 6-401, Toronto, Ontario, Canada. E: drlichtinger@yahoo.com

The concept of an intraocular lens (IOL) that can be adjusted in vivo has been hypothesised and studied since phacoemulsification became the standard of care in cataract surgery1 and its potential benefits have been recognised by previous investigators.2โ€“4 The first published report of a multicomponent IOL that could be adjusted after implantation came in 1996.5 Kraser2 patented a three-piece IOL with an inflatable diaphragm in which injection or removal of fluid from the flexible optic is used to post-operatively adjust the IOL power. Eggleston3 patented a mechanically adjustable IOL whose power is adjusted by rotation of the optic in a screw guide6 and later reported on the possibility of performing the adjustment non-invasively with the use of samarium and cobalt magnets.7

The development of the light adjustable lens (LAL) (Calhoun Vision, Inc, Pasadena, CA) started in 1996 with a collaboration by Daniel M Schwartz from the University of California, San Francisco and Robert Grubbs, Chemistry Professor at the California Institute of Technology (who subsequently won the Nobel prize in Chemistry in 2005), with the objective of creating a lens that was biocompatible, implantable through a small incision and capable of providing a stable, precise correction of myopic, hyperopic and astigmatic refractive errors within a reasonable power range while benefiting from a safe, non-invasive post-operative adjustment procedure.4

Design and Development

Silicone was selected for the LAL technology because of its optical clarity, ability to be folded during insertion and history of safe use in IOLs. The silicone formulation used in the LAL is based upon a silicone matrix system comprised of polymer, resin, crosslinker and platinum catalyst. Formulated into the silicone matrix are a photoreactive macromer, photoinitiator and ultraviolet (UV) absorbers. The photosensitive macromer system was designed to be compatible with the silicone matrix and insoluble in water to prevent leaching into the eye. It also was formulated to remain optically clear upon forming an interpenetrating network within the matrix upon irradiation with UV light.4

The LAL is a three-piece silicone lens with blue poly(methyl methacrylate) (PMMA) modified-C haptics. The optic has a diameter of 6 mm,8 a 360-degree square edge on the posterior surface to minimise posterior capsular opacification (PCO)9 and an enhanced UV protection layer in the posterior aspect to minimise erythropsia from retinal UV exposure.10

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Keywords: Light adjustable lens, cataract surgery, intraocular lens, intraocular lens calculation
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