JUL 2013

EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.

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46 EW REFRACTIVE SURGERY July 2013 Customized presbyopia solutions from the light-adjustable lens by Arturo Chayet, MD P resbyopia is an inevitable part of the aging process, yet the challenge it presents, precise correction of near vision with preservation of good distance vision, remains inadequately handled by existing solutions. Reading spectacles and contact lenses are universally accepted as a quick fix; however, active individuals and those who have been spectacle independent their whole lives often desire a more permanent, spectaclefree solution. Spurred by the needs of such individuals, the last two decades have brought an evolution in presbyopia treatment, and focus has turned to permanent solutions, namely presbyopia-correcting IOLs. Such multifocal and accommodating IOLs, however, have proven incapable of completely restoring sharp near vision without compromising distance vision and overall visual quality. The CNA approach The light-adjustable lens (LAL, Calhoun Vision, Pasadena, Calif.) is a novel presbyopic solution designed to avoid the current limitations of multifocal and accommodating IOLs. The lens, which is currently in phase 3 trials in the United States, is a monofocal lens composed of light-sensitive macromers that polymerize on exposure to ultraviolet (UV) light of a specific wavelength. This molecular reconfiguration triggers a change in lens shape, which in turn alters the lens' refractive power. The lens' malleable nature is key to its efficacy. Patients implanted with a LAL receive postoperative lens power adjustments until the exact level of refractive correction required is achieved. Although the lens is indicated for cataract treatment in addition to correcting many types of refractive error, its customized near add (CNA) technology also makes it the ideal solution for presbyopic patients. CNA involves the addition of precise amounts of refractive power to the central lens zone while sparing lens power in regions beyond this zone. Central addition of power boosts near vision and rectifies presbyopia-related vision complaints, without compromising the distance vision that is usually preserved in presbyopic patients. In addition, CNA treatment can be performed in The LAL implanted in the eye Source: Arturo Chayet, MD a stepwise fashion, in which patients are assessed after 15 seconds of light exposure and only receive additional central light exposure if their near vision requires further sharpening. This ensures that all patients receive an amount of CNA that is specifically tailored to their level of presbyopia. The lens' CNA function has undergone further refinement over the last year. No longer is it restricted to a photopic pupil size of at least 3.5 mm; patients with photopic pupils of any size are now eligible for CNA. Greater adjustment flexibility is also offered by the updated CNA function (CNA2), which can be applied as a primary adjustment to patients with astigmatism of less than 0.75 diopters (D) and an overall mean refractive spherical equivalent (MRSE) greater than –0.50 D at the first adjustment. Furthermore, a myopic adjustment can be applied after application of a CNA2 adjustment to correct for any myopic shift that may have been induced. The lens in practice My colleagues and I recently performed a study involving 14 presbyopic patients in our Mexico-based refractive practice. All underwent LAL implantation followed by at least one UV light lens power adjustment beginning at two weeks postimplantation. Second and third adjustments were performed 48 hours after previous adjustments. CNA2 was incorporated into the lens during a first or second adjustment and then followed by a myopic adjustment to fix any myopic shift from the CNA2 adjustment. Finally two UV light exposures to "lock in" the final lens power were performed. At one week post lock-in number two the percentage of eyes with a monocular uncorrected distance visual acuity (UDVA) of 20/25 or better improved from 28.6% (4/14) at pre-adjustment to 85.7% (12/14). Likewise, the monocular uncorrected near visual acuity (UNVA) improved from 14.3% (2/14) at pre-adjustment to 100.0% (14/14) at one-week post lock-in number two. One week following lock-in number two, the percentage of the group with a binocular uncorrected distance visual acuity (UDVA) of 20/25 or better was 92.9% (13/14) before adjustment and 92.9% (13/14) at one week post adjustment. A binocular uncorrected near visual acuity (UNVA) of J3 or better was present in 57.1% (8/14) of the group pre-adjustment; however, this percentage rose to 100.0% (14/14) at one week post lock-in number two. These results illustrate just how effective the lens' CNA2 capability is at restoring sharp near vision in presbyopic patients without any need for postop use of spectacles. Case study Patient JH, a 58-year-old male and former NASA engineer, presented to our clinic with presbyopia. He had very high visual demands and desired a spectacle-free method of achieving crisp near vision. He had no problems with his distance vision and wanted it to remain clear postoperatively. He underwent LAL bilateral implantation, after which he had an uncorrected distance visual acuity of 20/30 in his right eye, 20/25 in his left eye, and an uncorrected near visual acuity of J6. His right eye was adjusted for distance vision and after two adjustments and two lock-ins, his distance visual acuity improved to 20/15. His left eye received a CNA2 adjustment and after three total adjustments and two lock-ins, his distance vision im-

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