Eyeworld

EW RESIDENTS July 2014 53 was performed 2 weeks after surgery. The second adjustment, or the first lock-in, was performed 2–3 days later. After the second lock-in was performed, the patient was seen at 1 month, 3 months, 6 months, and 1 year. Wavefront aberrations were measured using a near-infrared Hartmann-Shack wavefront sensor and were then expressed by Zernike coefficients for a 3.0 mm pupil. Objective refractions for both the whole eye and the cornea were cal- culated from the 2nd order Zernike coefficients. From 5 wavefront aberration measurements, the mean values of the refractions were calculated. The corneal refraction was defined as the corneal power and its astigmatism. The refractive changes of the internal optics of the eye (i.e., the IOL) were calculated by subtracting the anterior corneal re- fraction from the ocular refraction. To calculate the effects of the treat- ments on the eye and cornea, the refraction before treatment and after treatment with the opposite sign were combined. A standard phoropter was used to determine the subjective refraction. The corrected distance visual acuity (CDVA) and uncorrected distance visual acuity (UDVA) were measured and expressed as decimal units. Results Using the results from 53 eyes from 49 patients, each of the 8 light spa- tial patterns tested produced a differ- ent (statistically significant, p<.01) refractive change for both first and second treatments. Spherical profiles produced statistically significant changes to correct myopia and hy- peropia. The neutral adjustment pattern did induce small orders of myopia. Astigmatic correction pro- files changed both sphere and cylin- der at statistically significant levels (p<.01), with axis errors below 9 degrees, showing an efficacy of cylinder correction of 70%. Lock-in treatments produced a mean myopic shift of 0.33 D in eyes receiving one adjustment except in the hyperopic astigmatic (HA) pro- file, in which the myopic shift was negligible. The majority of this in- duced myopic shift occurred after the first lock-in. Lock-in treatments did not produce any significant changes in astigmatism. In all eyes, the mean sphere was +0.86±1.16 D before the first adjustment, which decreased to +0.21±0.57 D after all treatments. Astigmatic adjustments decreased the cylinder from –1.55± 0.36 down to –0.53±0.30 D. Mean spherical equivalents dropped from +0.28± 1.16 D down to –0.11±0.57 D. UDVA improved significantly with decimal values improving from a mean of 0.64±0.21 to 0.96±0.19. Over time, the mean change in spherical equivalent was 0.00 D. Discussion The light-adjustable IOL represents a new category of IOL and a viable alternative to manage postoperative residual refractive errors. This paper demonstrates relative stability of refraction of the eye, lens and cornea after implant, adjustment, and lock-in of the lens. The authors present an analysis technique using Hartmann-Shack aberrometry to measure the refractive state of the whole eye as compared to the refrac- tive power of the anterior surface of the cornea as measured by corneal topography. The refractive effect of the light-adjustable lens and the sta- bility of the lens effect are calculated using these measurements. This study provides new and useful information, but several limi- tations should be noted. The subject characteristics are not adequately described, and this may hinder the ability to apply this information to other patients. Similarly, no control group was provided. It would have been interesting to know how the LAL cohort outcomes would com- pare to a similar group of non-LAL patients having cataract surgery by the same surgeon with standard IOLs. Some might criticize the rela- tively early intervention for adjust- ment of the light-adjustable IOL at 2 weeks. Instability of refraction this soon after cataract surgery due to such factors as lack of complete healing of a 3.5 mm clear corneal incision or perhaps minor shifts in lens position due to contraction and/or fibrosis of the capsular bag could affect accuracy of treatment. A limitation in the lens technology itself is the roughly 2 D range of potential adjustment for myopia, hyperopia, and astigmatism. There are a few unknowns from this study that require further assessment and monitoring. A my- opic shift was noted after the lock- ins and two theories were brought up: 1. anterior axial movement of the lens based on anterior chamber depth measurements, or 2. variable UV penetration through the cornea to the intraocular lens. Specific properties of the cornea might play a role leading to differences in UV transmission. The authors did not investigate these theories and it would require further studies to determine the true cause of this myopic shift. Another concern is the potential UV exposure to the retina. The lens has a UV blocking surface on the back edge, but some patients report mild retinal symptoms in the few days after lock-in. All of these symptoms resolved within 1 week. The low amount of UV exposure is unlikely to cause permanent damage to the retina, but this needs to be monitored. Impressively, 80% of patients had a final spherical equivalent of 0.50 D or lower with excellent stability at 1 year in this study of the light-adjustable lens. Another re- cent study by Simon and colleagues found that in postoperative cataract surgery patients without pre-existing ocular disease, 98.8% achieved ±1 D of target refraction using currently available IOLs. This reminds us that our current IOL technology also yields excellent results. We should remember other treatment options for managing postoperative refrac- tive errors including glasses, contact lenses, and refractive surgery. Our current standard of care for cataract surgery provides relatively accurate refractive results. Any new technol- ogy going forward must not only produce equal or superior results, but also be a cost effective treatment in this current healthcare environ- ment. According to an article in the October 2011 issue of EyeWorld, the estimated cost of the light-adjustable IOL is $1,446. This study adds to the body of evidence demonstrating safety and efficacy of the Calhoun LAL. This addition to our IOL armamentarium would perhaps initially be best suited for use in patients where IOL power predictability is known to be less accurate such as in patients with prior radial keratotomy or laser vi- sion correction surgery. There are aspects of the light-adjustable IOL that need monitoring and further study, but the overall results are very promising. EW References 1. Simon SS, Chee YE, Haddadin RI et al. Achieving target refraction after cataract sur- gery. Ophthalmology. 2014 Feb;121(2):440–4. 2. Young, M. October 2011. Evaluating the Light Adjustable Lens. Retrieved from eyeworld.org/article.php?sid=6066. Contact information Mifflin: mark.mifflin@hsc.utah.edu "There are aspects of the light-adjustable IOL that need monitoring and further study, but the overall results are very promising." 50-53 Residents_EW July 2014-DL_Layout 1 6/30/14 8:49 AM Page 53

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