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
Arthur A. Medina
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
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.
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
doctors 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
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
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. Weve had a lot
of patients say wow. Many comment that it is the clearest they have
Dr. McQuillans 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.
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
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
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;
- Jeff G. Hopkins is senior manager for professional affairs at Carl
Zeiss Vision Inc. He can be reached at (858) 790-7700, ext. 1243;
- Shui T. Lai, PhD, is founder and CEO of Vmax Vision Inc. He can be
reached at (888) 413-7038; firstname.lastname@example.org.
- Arthur A. Medina Jr., OD, can be reached at (210) 225-4141;
- Michael H. McQuillan, OD, can be reached at (805) 484-0577;
- 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