University of Rochester Wavefront Sensing Technology Zywave Aberrometer and Customized Ablation

For the past 200 years, nearsightedness, farsightedness and astigmatism were the only optical errors of the visual system that could be measured and treated. Doctors and scientists always suspected that there were more imperfections of the eye’s optical system, but we could not find them. In 1997, with the development of the wavefront sensor by Dr. David Williams and his team at the University of Rochester’s Center for Visual Science, these so-called higher order aberrations could be identified. Instead of just measuring the lower order aberrations (nearsightedness, farsightedness and astigmatism), up to 64 different higher order aberrations could be detected and measured. Ongoing research at The Center for Visual Science and StrongVision is determining that approximately 90% of the eye’s optical imperfections are due to lower order aberrations with the rest being made up of the 64 higher order aberrations.

Technician Brenda Houtenbrink measures a patient's optical errors using the Bausch & Lomb Zywave.

The team at StrongVision along with the scientists at the U of R’s Center for Visual Science and Bausch and Lomb have taken wavefront sensing to the next level and learned how to apply the data derived about a patient’s higher order aberrations to laser vision correction. Dr. MacRae and the Alliance for Vision Excellence team of physicians, scientists and researchers meet on a weekly basis developing ways to refine wavefront sensing and customized ablation refractive surgery to optimize visual results and increase the safety of surgery for StrongVision patients.

How Do Higher Order Aberrations Impact Vision?
Everyone has a certain degree of higher order aberration in their visual system that may affect the way they see. The University of Rochester team has determined that people with significant higher order aberrations may not see perfectly, even with the best glasses, contact lenses or refractive surgery possible. Two common and potentially disruptive higher order aberrations are Spherical Aberration and Coma. Spherical aberration creates halos around points of light while coma makes points of light appear comet-like with a blurry tail-like smudge to them.

Higher order aberrations are detected with a wavefront sensor that was developed by Dr. Williams’ laboratory and is being commercially marketed by Bausch and Lomb as the Zywave. By beaming a low power laser light into your eye and measuring the shape of the reflected wavefront of light, the Zywave can analyze your lower and higher order aberrations in less than 2 seconds.

The display of the Zywave describes your basic prescription, your pupil size and provides a full analysis of your higher order aberrations. All patients evaluated for refractive surgery at StrongVision are tested with the Zywave Wavefront Sensor. Use of this system enhances patient safety. The StrongVision team has as much experience with wavefront sensing as any clinical group in the world. They were instrumental in developing and refining the Zywave system.

Applying Wavefront Technology to Treatment

When performing customized ablation we take data from the wavefront sensor and use it to program the excimer laser. By treating both lower and higher order aberrations, StrongVision’s research with Zyoptix, Bausch & Lomb’s customized ablation system has shown that after surgery with the Zyoptix system 91.5% of eyes treated had unaided vision of 20/20 or better and 70.3% had unaided vision of 20/16 or better. Dr. MacRae and the StrongVision team were the second group in the United States to use the wavefront sensor to create a customized ablation treatment and the first group to perform an independent FDA study with the technology. Zyoptix was approved for use by the US FDA on October 10, 2003. Using the University of Rochester Nomogram advanced treatment planning software, developed by Dr. MacRae and his research team, nearly 97% of patients having customized ablation treatment see 20/20 or better without glasses. This advanced treatment software is currently not available anywhere else in the world but here at StrongVision.

Improvements in vision with customized ablation are in the quality of vision achieved, with patients noting improved sharpness particularly under low light conditions. Patients with significant levels of pre-operative higher order aberrations may be the best candidates for customized ablation.

Every patient seen at StrongVision is tested with the Zywave to measure their higher order aberrations. Customized ablation may not be for everyone, but by utilizing this technology today, Dr. MacRae and the StrongVision team can decide which type of refractive surgery is safest for you.

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