Eyeworld

35 EW REFRACTIVE SURGERY December 2015 by Stefanie Petrou Binder, MD, EyeWorld Contributing Writer Near vision: not just about accommodation P resbyopic patients benefit from a range of valid solu- tions to restore near vision and achieve spectacle inde- pendence. Although their power of accommodation cannot be restored, different ways to compen- sate for the loss of accommodation have emerged that take into account numerous optically relevant factors. Paramount to any solution is an understanding of which measure- ments to make and how to interpret them, as discussed during a clinical research symposium on the topic at the XXXIII Congress of the Europe- an Society of Cataract & Refractive Surgeons (ESCRS). Subjective "The goal is to win back near visual acuity and improve reading func- tion. Choosing the right solution for your patient requires an in-depth examination of the patient's unique optical system," said Alois K. Dexl, MD, Salzburg, Austria. "There is an important distinction to be made between subjective and objective ac- commodation measurements. While reading function is best measured subjectively, true accommodation can only be proven through objec- tive measurements." By targeting certain variables when testing a patient's reading function such as varying reading distances, illumination, contrast, reading speed, print size, and monocular versus binocular tests, Dr. Dexl achieves a better sense of what sort of correction best suits the patient. He recommends testing at lower contrast levels (70–75%), low- er illumination, and smaller print sizes before deciding on the correc- tive strength to approximate the reading conditions of everyday life and ensure the patient is satisfied with the correction. Logarithmically scaled reading charts such as the Salzburg Reading Desk (SRD Vision) are particularly important, although their use is not universal, and testing patients at the appropriate reading distance is crucial. Dr. Dexl also relies on the sub- jective results of defocus curves, near visual acuity exams, reading func- tion outcomes, and patient feedback to assess expectations, to choose the presbyopic correction that best suits his patient. Objective Objective measurements provide vital information about accommo- dative and pseudoaccommodative capabilities and the overall optical system. For an objective assessment of accommodation, physicians use autorefractometers, retinoscopy, Scheimpflug-camera based systems, and ultrasound biomicroscopy or anterior segment OCT imaging during accommodative efforts, to name some available modalities. "Pseudoaccommodation allows the attainment of functional near vision in an emmetropic or distance- corrected eye without changing the refractive power of the eye," said Ioannis G. Pallikaris, MD, Heraklion, Greece. "It is a complex phenomenon that can be attributed to several static factors like pupil size, against-the-rule cylindrical refractive error, and multifocality of the cornea, and dynamic factors, such as the anterior movement of the implant itself. The iTrace [Tracey Technologies, Houston] can pro- vide much of this information and more." Using the the iTrace ray tracing wavefront aberrometer, Dr. Pallikaris determines a patient's accommo- dative and pseudoaccommodative capabilities by measuring a dynamic accommodation range in real time and a wavefront depiction of the entire optical system. The iTrace helps to streamline preop assessments by accurately de- picting the patient's optical system alignment, allowing the physician to recommend multifocal or monofocal lens solutions. It also can determine if a patient's aberrations originate in the cornea or the lens. Minimal cor- neal higher order aberrations speak well for a premium IOL. Addition- ally, the iTrace shows if a patient's internal optics compensate for any corneal astigmatism and allow treat- ment adjustments. Postoperatively, the patient's visual performance can be mapped with iTrace and analyzed for treatment success. "Understanding accommoda- tion is complex. From the physio- logic and anatomic perspectives, we still have a lot to learn, but from the optic point of view, ray tracing gives measurements that allow us a better understanding of accommodation," Dr. Pallikaris said. Variables According to David Spalton, FRCS, London, pseudoaccommodation can be confounding, as a patient's near vision may appear to be improved without accommodation actually occurring. "The problem is that there is more to near vision than accommodation. Improved reading ability is no evidence that accom- modation is occurring. You have to prove that something is happen- ing physically, causing a change in refraction. Accommodation is a dynamic change in refraction, while pseudoaccommodation involves an increased depth of focus. Further- more, an objective measurement of accommodation is difficult because much of the technology is quite new and can be unreliable to measure accommodation." He explained that the depth of focus can vary depending on the measuring technique used and the patient's pupil size. Less spherical aberration and vertical coma reduces the depth of focus for near vision by about 0.46 D. Pupil constriction from 6 mm to 4 mm reduces higher order aberrations by 70%. "We need to look at the assess- ment of near vision in a very critical and controlled way, by controlling variable factors, objective measure- ments, and through prospective randomized controlled trials." Variables include non-IOL environmental factors like illumina- tion, contrast, and spatial frequency; ocular factors such as pupil miosis, astigmatism, higher order aberra- tions, and residual myopia; and cortical factors like visual processing and patient motivation. "Accommodation and near vision need to be supported by scientific studies. It is important that the ophthalmic community come together to understand which factors affect near vision. Restoring accommodation is the holy grail of cataract surgery, and we are several years away from actually achiev- ing it, although I am sure that it is achievable," Prof. Spalton said. EW Editors' note: Dr. Dexl has financial interests with SRD Vision. Dr. Pallikaris has financial interests with Tracey Technologies. Prof. Spalton has financial interests with Anew Optics (Newton Centre, Mass.), and Santen/Advanced Vision Science (Goleta, Calif.). Contact information Dexl: a.dexl@salk.at Pallikaris: pallikar@med.uoc.gr Spalton: profspalton@gmail.com continued on page 36 by Ellen Stodola EyeWorld Staff Writer Are LASIK numbers declining? Experts offer suggestions on what can be done about a decline in LASIK procedures A re LASIK numbers de- clining across the board? Many seem to think so, including three surgeons who commented in this article. They indicated that a number of factors may play into a decline in LASIK surgery numbers and share what they think can be done to revive the procedure. Manoj Motwani, MD, Motwani LASIK Institute, San Diego, thinks that LASIK numbers are way down. "Before the recession, we were doing 1.4 million eyes annually in the United States," he said. "For the past

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