New breed of refractors much more precise

Developments in this technology allow for refractions to 100ths of a diopter.

Aberrometers once limited to measuring higher-order aberrations in refractive surgery patients, such as with custom LASIK procedures, have now shifted from the surgical suite to traditional exam lanes, thanks to the recent availability of two new technologies that provide much more accurate subjective manifest refraction.

Arthur A. Medina Jr.

Instead of measuring in customary 0.25-D increments, the i.Scription package (Carl Zeiss Vision, San Diego) and PSF Refractor (Vmax Vision, Orlando, Fla.) allow clinicians accuracy “to 100ths of a diopter,” Arthur A. Medina Jr., OD, a Primary Care Optometry News Editorial Board member in private practice in San Antonio, Texas, told PCON.

Dr. Medina has used both systems. “I find them to be comparable in outcomes, but they accomplish it by two different mechanisms,” he said.

The i.Scription and PSF Refractor are strictly refracting instruments, Dr. Medina noted. “There is only one way to obtain a subjective manifest refraction, and it requires a subjective response from the patient, which both of these new systems provide,” he added.

i.Scription

A major component of i.Scription is the i.Profilerplus, a combination device of autorefractor, corneal topographer and wavefront aberrometer (a Shack-Hartmann aberrometry approach).

“The i.Profilerplus basically refracts the patient at various pupil sizes by shooting a beam of light into the eye, then measures the light coming back using 1,500 receptors, whereas with standard subjection refraction you measure only one pupil size,” Jeff Hopkins, senior manager for professional affairs at Carl Zeiss Vision, said in an interview.

“During the 1-minute measurement process, the device maps the higher-order wavefront aberrations of the eye,” he said. Afterward, i.Scription software takes the data to “essentially refine the doctor’s subjective refraction. The device determines the best prescription over the full range of pupil sizes. It strikes a balance between night-time vision and daytime vision. Your daytime vision will be as good as ever and night-time vision will be improved.”

I.Scription debuted in October 2010 and will particularly benefit spectacle wearers with significant higher-order aberrations or anyone who complains about night vision, according to Mr. Hopkins.

“The i.Profilerplus measures precisely out to 1/100th of a diopter,” he said. “This is an opportunity for a doctor who dispenses eyeglass lenses to bring another benefit to his patient with a more premium product.”

I.Scription is available on all customized progressive and single-vision lenses from Carl Zeiss Vision, as well as Reveal Freeform lenses from Vision Service Plan (VSP). The i.Profilerplus and i.Scription software are also currently available to the approximately 27,000 private providers contracted with VSP.

Michael H. McQuillan, OD, in private practice in Camarillo, Calif., has been using i.Scription since January. “The wavefront analysis is amazing,” he said. “Someone with significant wavefront aberrations will respond well to the truly customized free-form lens. We’ve had a lot of patients say ‘wow.’ Many comment that it is the clearest they have ever seen.”

Dr. McQuillan’s favorite example is a patient in her 80s who attends UCLA basketball games with her son, a sports writer. Since being fitted with the lenses, she remarked that “for the first time she has a panoramic view of the inside of the stadium,” Dr. McQuillan said.

By adding wavefront analysis to standard refraction via i.Scription software, “I can tell easily and demonstrate to the patient easily the benefit of the customized lens,” Dr. McQuillan said. “But it is important that every measurement done in conjunction with these new lenses – seg height, PD, back vertex distance, pantoscopic tilt and frame wrap – be precise to the 10th of a millimeter for maximum benefit. With less precise measurements, we had less success.”

PSF Refractor

“Many ODs have been waiting for the day when they will no longer need to use the classical mechanical phoropter,” Shui T. Lai, PhD, founder and CEO of Vmax Vision, told PCON. The PSF (point spread function) Refractor, which launched in March, is “an evolutionary technology that replaces the current phoropter,” he said. “It is five times more accurate, in that we refract the patient down to 0.05 D. The point spread function fundamentally improves the sensitivity for the patient to be able to discern this difference.”

Like a phoropter, the PSF Refractor is a subjective device that requires patient participation, as opposed to the objective readings of wavefront aberrometry or autorefraction.

“Measuring vision with an objective device is basically measuring the physical characteristics of the optics of the eye, whereas a subjective device not only integrates the optical characteristics of the eye – the retina – but the neural function as well,” Dr. Lai said. “Subjective testing provides a more reliable reading.”

Measuring vision with the PSF Refractor takes about 1 minute for each eye. The see-through optical system allows patients to view a real-world PSF target, rather than a Snellen eye chart.

Complementing PSF refraction are Encepsion lenses, which are premium free-form lenses available as progressive or single-vision lenses.

“Our progressive design is state-of-the-art and 100% customizable,” Dr. Lai said. “The lens is programmable point by point when created on the back surface, so it matches the accuracy of the 0.05 D of the PSF Refractor.”

Because PSF refraction is so accurate, Vmax Vision is exploring the possibility of using the system in refractive surgery for results comparable to wavefront-guided LASIK. Another likely application is high-precision target shooting for the military.

“It is much easier for patients to respond to the PSF Refractor,” David I. Geffen, OD, a private practitioner from San Diego, said in an interview. “In addition, it is easy to delegate.”

Dr. Geffen has used the refractor on more than 1,000 patients since the spring of 2010. He has four wavefront aberrometers in his office; however, “none of them come close to subjective refractions,” he said.

With the PSF Refractor, “my patients are getting a more accurate prescription and they are seeing crisper with the Encepsion lenses,” he said. “Patients who I thought were seeing well at 20/20 are now coming in at 20/15 to 20/12.”

Patients appreciate the advance in technology, Dr. Geffen said. “The phoropter is the oldest piece of equipment in the office,” he said. “The high-tech feel and look of the PSF Refractor brings refraction into the 21st century.”

As an aside, Dr. Geffen underwent carpal tunnel surgery about 18 months ago. His surgeon felt it was caused in large part by the daily routine of refracting with a phoropter.

“The PSF Refractor is much less stressful on the doctor because you are sitting in a comfortable seat using a small laptop computer to refract vs. bending over and spinning dials all day long,” he said.

He predicts that eventually even prescriptions for contact lenses will be based on a refraction device such as the PSF Refractor.

Better patient care

“As vision clinicians, it is important that we become knowledgeable about high-order aberrations,” Dr. Medina said. “Once we are able to access and evaluate these aberrations, we can provide better care for the patient. ”

Dr. Medina also predicts tougher standards for spectacle lens manufacturers. “I firmly believe that lens makers who decide to switch to a certified registered lens within 1/100th of a diopter represent the lenses of the future,” he said. – by Bob Kronemyer

• David I. Geffen, OD, can be reached at (858) 455-9950; dig2020@aol.com.
• Jeff G. Hopkins is senior manager for professional affairs at Carl Zeiss Vision Inc. He can be reached at (858) 790-7700, ext. 1243; jeff.hopkins@vision.zeiss.com.
• Shui T. Lai, PhD, is founder and CEO of Vmax Vision Inc. He can be reached at (888) 413-7038; slai@vmaxvision.com.
• Arthur A. Medina Jr., OD, can be reached at (210) 225-4141; art.medina@ymail.com.
• Michael H. McQuillan, OD, can be reached at (805) 484-0577; drmcq@irishidr.com.
• Disclosures: Dr. Geffen is a paid consultant and investigator for Vmax Vision. Dr. Medina is a paid consultant to Carl Zeiss Vision and an investigator for VMax Vision. Dr. McQuillan has no direct financial interest in the products mentioned, nor is he a paid consultant for any companies mentioned.