Premium IOL brain booster: Considering neural testing and plasticity
August 2011‧Eye World
Premium IOL brain booster: Considering neural testing and plasticity
by Maxine Lipner Senior EyeWorld Contributing Editor
Neurological keys to bumping up performance of advanced lenses
Unfortunately, in terms of pre-op neural testing to see who might be a good candidate for a premium lens, there really aren't standard objective measurements that exist today, according to George O. Waring IV, M.D., corneal, cataract, and refractive surgeon, Revision Advanced Laser Eye Center, Columbus, Ohio, and medical director, division of ophthalmology, St. Joseph's Translational Research Institute, Atlanta. Practitioners must instead rely on objective measurements from the eye itself, such as aberrometry, angle kappa, manifest refraction, and health of the ocular surface, in determining good candidates. "The clinician develops a gestalt over time as to which patients tend to do better with multifocal lenses," Dr. Waring said. "Weighing what they do in their daily activities is also very important." So, for example, someone who drives at night for a living might not be the best candidate.
Premium testing
In addition to typical testing, practitioners now have the ability to tap more sophisticated avenues, such as the use of double-pass wavefront technology, to help understand the role of light scatter. With the device known as OQAS (Optical Quality Analysis System, Visiometrics SL, Terrassa, Spain), Dr. Waring finds that he can offer an objective assessment of potential visual quality with premium lenses. "That can give you a sense of the role of light scatter in an eye," he said. But this information is still in the optical, not the neural, level. However, Dr. Waring sees this as one more factor that can lead practitioners to believe that someone is a good candidate for a premium IOL.
Likewise, the role of centration can be particularly important with premium IOLs. Dr. Waring sees the new KAMRA Inlay (AcuFocus, Irvine, Calif.) as making big strides here in helping to identify the estimated line of sight. As part of the AcuTarget System used for implantation, a real-time video overlay is displayed to show practitioners the proper surgical placement of the inlay. But such a system may also be applicable to premium IOLs as well. "It's just as important for a multifocal IOL to be placed in the right position, particularly in a patient with higher degrees of angle kappa, and also to screen out subtle things such as monofixation syndrome," Dr. Waring said. "These are critical components that lead up to who's going to do well and who's going to neuroadapt well with these advanced technologies."
Since such testing may or may not be covered by insurance, this can present practitioners with a bit of an ethical issue in cataract cases. Should practitioners, for example, do a full evaluation of the tear film and macular health on all patients? And what about topography; is this justified? When it comes to these premium lenses, Dr. Waring thinks so. "You have to know what you're dealing with on every aspect of the eye or else the IOL may not perform like you want it to," he said. "In my mind it's in the best interest of the patient; if you're going to use that advanced technology, you need a front-to-back assessment that gives you a healthy checkmark all the way through and that includes these advanced testing modalities."
Visual cortex training
Moving beyond diagnostics, one new avenue opening up is the idea of visual cortex training. The idea is to help the brain to neural adapt to the premium lenses by enhancing visual signals. Elkhonon Goldberg, Ph.D., clinical professor, department of neurology, NYU Medical School, thinks that the brain may have a possible role here. "When we talk about the neural substrates of the visual system, we talk about the retina, we talk about certain nuclei in the brainstem and certain nuclei in the thalamus, and finally, we talk about certain cortical areas," Dr. Goldberg said. "My expertise pertains to this kind of higher cortical level of visual processing, and there is a certain degree of plasticity."
When it comes to patients who have experienced strokes or injuries involving the visual system, there has certainly been a role for various cognitive exercises. "Cognitive rehabilitation in the form of various structured cognitive exercises has been around since the days of World War II," Dr. Goldberg said. "In the olden days it was basically a paper and pencil endeavor and now it is increasingly software-based. In principle, these tools are moderately effective." Potentially, Dr. Goldberg sees well-designed cognitive exercises as possibly benefiting normal individuals as well.
Some new visual cortex training software from RevitalVision (Lawrence, Kan.) has recently emerged. "It's a computer software-based biofeedback system that continuously adapts to individual visual ability and essentially optimizes visual processing," Dr. Waring said. This web-based software is prescribed by the practitioner for the IOL patient to use at home. This typically is a 2-month treatment program. "It takes about 20 different sessions of about 20 minutes each at the computer in a dark room," Dr. Waring said. He recently took part in a pilot study trying to gauge the effect of using this software for different IOLs. "We had the idea, what if we take a series of patients with different IOLs, including multifocal and accommodative IOLs, and give them a month of normal healing, which can allow for some natural neural adaptation, and then measure baseline uncorrected acuities for distance and near and contrast sensitivity for distance and near," Dr. Waring said. In this multicenter trial involving 62 eyes, patients using five different types of IOLs were asked to undergo 2 months of cortical visual training. After this they were remeasured. "What we found was that we basically had just over one line of improvement in distance acuity and just under one line of improvement in near acuity," Dr. Waring said. "There was also about 170% improvement in contrast sensitivity at distance and about 100% improvement in contrast sensitivity at near."
In addition to comparing results to the patients' pre-op levels, efforts were made to compare results for those who had undergone the training to those who had simply been left to their own devices. In this case, results from a subset of Crystalens (Bausch & Lomb, Rochester, N.Y.) patients who didn't have any training at all were reviewed at the same time point. "We have statically significant results that showed that there was no improvement at all in distance or near acuity in the untrained group," Dr. Waring said. "This doesn't demonstrate efficacy, but the results were encouraging."
Likewise, another group led by Joao Marcelo Lyra, M.D., Ph.D., Maceio, Brazil, did a similar study concentrating on the ReSTOR (Alcon, Fort Worth, Texas) multifocal lens. In this study, investigators waited 6 months after lens implantation before starting patients on the visual cortex training. This training lasted for 2 months. Results were likewise encouraging. "He saw a boost of around 130-150% for contrast sensitivity and about one line to one and a half lines of improvement in acuity," Dr. Waring said. "Here is a separate group with a separate study that showed that we can use different time points. He waited longer to allow for that natural neural adaptation and he saw the same improvement."
Dr. Waring sees the visual cortex training as akin to physical therapy after something such as hip surgery. "You undergo physical therapy; you don't go straight out onto the basketball court," he said. "This is basically visual rehabilitation." He sees the data as promising. "Although the data is preliminary, it is encouraging," Dr. Waring said. "We have a prospective, randomized, control trial underway."
While currently technology is limited when it comes to factoring in the neural component with premium IOLs, that is likely to change in the future. Dr. Waring pointed to work being done on adaptive optics simulators. In the future, Dr. Waring thinks that this will help practitioners to determine who may or may not adapt well to premium lenses. "They'll be able to simulate an optical circumstance so at least they get a feel here," Dr. Waring said. "Then, more importantly, they'll be able to tailor treatment to the needs and preferences of patients and potentially design a treatment program because they can dial in the higher-order aberration profile that suits the needs to balance depth of focus and quality of vision."
Overall, Dr. Waring is very optimistic. "With adaptive optics, visual simulators, and the devices that help us to better define placement and line of sight, in conjunction with visual rehabilitation and cortical training, we're going to be able to deliver superb results in a much more predictable manner," he said.
Editors' note: Dr. Waring has financial interests with RevitalVision. Dr. Goldberg has no financial interests related to his comments.
Contact informationGoldberg: 212-541-6412, egoldb7407@aol.com
Waring: 614-781-0499, georgewaringiv@gmail.com
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