EyeWorld India December 2013 Issue

34 EWAP rEfrActivE December 2013 suggested reading list). “Spherical aberration increases depth of focus and has a positive impact on presbyopia correction,” she said. “AO technology can simulate the right amount of spherical aberration that would not interfere with the patients’ distance vision and still increase their depth of focus and pseudoaccommodation.” She predicts this type of simulation will be used in the office as a means of managing patient expectations. Possible uses AO will likely have the most use in refractive surgery, but other areas hold potential as well. “Wavefront- correcting IOLs (neutral and with negative spherical aberration) compensate for the cornea, which has an average aberration of 0.28 µm for a 6.5-mm pupil diameter. But one size does not fit all, and using AO will give us a better picture of the aberrations and, therefore, will help us provide even better visual outcomes,” Dr. Rocha said. AO technology has potential for customized refractive surgery and presbyopic corneal and lens-based treatments, customized contact lens corrections, and wavefront customized IOL implantation, she said. AO technology can also be applied to retinal imaging, microperimetry and even microlaser treatments, she said. “AO will increase the resolution of retinal imaging devices by a factor of 10, revealing previously invisible retinal microstructures.” There’s been a few studies published on reflectance of cones, photoreceptor density and microvascular activity, and more are likely to come, Dr. Rocha said. EWAP Editors’ note: Dr. Rocha has no financial interests related to this article. contact information rocha: +1-216-445-2020, karolinnemaia@ gmail.com Using - from page 33 Myoung Joon KIM, MD Associate Professor, Asan Medical Center 88 Olympic-ro 43-gil, Songpa-gu, Seoul 138-736, Korea Tel. no. +82-2-3010-3975 Fax no. +82-2-470-6440 joon@amc.seoul.kr “T winkle twinkle little star…” Why do stars twinkle? What a dry question from such a beautiful song. The reason for twinkling is atmospheric turbulence. We cannot get clear detailed images of stars because they twinkle. Can optical aberrations induced by the atmosphere be corrected? Adaptive optics (AO) can do it. AO was originally used in the military and astronomy to compensate for the wavefront distortion induced by atmospheric turbulence. AO consists of two key components: a wavefront sensor measuring the aberration, and a deformable mirror to correct the aberration through the closed control loop. The deformable mirror is capable of actively shaping the mirror surface by pushing or pulling electrostatic actuators attached to the back surface of the mirror. With AO correction, diffraction-limited images of stars can be achieved in real time. In the field of ophthalmology, AO was first applied to high resolution retinal imaging in the late 1990s. Images of retinal cells could not be taken even with the finest ophthalmoscope due to the eyes’ optical aberrations. AO compensates for the eyes’ optical aberrations, allowing us to get sharper images of retinal cells. More recently, AO has also been used in vision simulators. With the same AO principle, it can simulate various optical correction conditions to evaluate the effects of the aberration on vision and visual benefits of correcting higher order aberrations (Figure). It can also intentionally induce an aberration to understand the visual benefit of advanced refractive and cataract surgical techniques as presbyopia solutions. Through the AO system, patients can experience targeted optical conditions before the surgery. The price of a deformable mirror has been a barrier to the clinical use of AO. Its price has been lowered slowly but it is still expensive. For this reason, most AO systems are currently in the laboratories. That said, I believe they will come to clinics from benchtops in the near future due to a wide variety of potential applications. Editors’ note: Prof. Kim has no financial interests related to his comments. Views from Asia-Pacific The principle of Adaptive Optics can simulate various optical correction conditions to evaluate the effects of the aberration on vision and visual benefits of correcting higher order aberrations. Source: Myoung Joon Kim, MD