microelectromechanical systems– (MEMS-) based adaptive
MILLIONS of people use eyeglasses
or contact lenses to correct their vision, and many are opting
laser eye surgery. But determining the needed correction is not
an exact process. When we have our eyes checked, we sit in a
darkened room, peer through a device called a phoropter, and
look at a focusing target, often an eye chart, projected in front
of us. As we read the chart, an optometrist or ophthalmologist
changes the lenses we’re looking through while we repeatedly
answer the doctor’s only question: “Which one looks
better—number one . . . or number two?”
new optical device, called the microelectromechanical systems– (MEMS-)
based adaptive optics phoropter (MAOP), will greatly improve this
process. It allows clinicians to integrate a computer-calculated
measurement of eyesight with a patient’s response to the
target image. Patients can immediately see how objects will look—and
the clinician can adjust the prescription—before they are
fitted for contacts or undergo surgery. As a result, patients will
experience better vision correction outcomes, especially with custom
contact lenses or laser refractive surgery.
was developed in a collaboration among universities, national laboratories,
and industry, including a team of researchers from
Lawrence Livermore. Funded by the Department of Energy and the
Center for Adaptive Optics—a National Science Foundation
Science and Technology Center—the project brings together
optical component manufacturers and one of the world’s leading
providers of custom contact lenses and refractive eye surgery equipment.
The MAOP team received an R&D 100 Award for developing an eye-correction
system that combines technologies to improve the diagnosis and
treatment of eyesight aberrations and ophthalmic and retinal disease.
Livermore members of the MAOP team
(left to right): Scot Olivier, Steve Jones, Kevin O’Brien,
Don Gavel, Abdul Awwal, and Brian Bauman.
An Objective Measure of Eyesight
current phoropter used to measure vision addresses only the lower-order
aberrations, such as defocusing and astigmatism. MAOP
is designed to help patients with higher-order problems, such as
coma, spherical aberration, trefoil, and quadrifoil. Scot Olivier,
who led Livermore’s MAOP effort, says future versions of
the system will incorporate retinal imaging, so clinicians can
more successfully diagnose and treat retinal diseases—such
as retinitis pigmentosa, glaucoma, diabetic retinopathy, and macular
degeneration—that cause blindness.
combines adaptive optics technology—a technology used
on the world’s largest telescopes for high-resolution imaging
of astronomical objects—with MEMS deformable mirror technology.
By using the MEMS deformable mirror, says Olivier, the team significantly
reduced the size of the phoropter and could build it with commercial
components, thus making MAOP compact and affordable.
optics compensates for optical aberrations by controlling the phase
of the light waves, or wavefronts, as they hit the retina—much
like waves breaking on a shoreline. The optical structures in the
eye, particularly the cornea and lens, can distort these wavefronts
and thus produce the aberrations we encounter in our natural vision.
An adaptive optics system measures aberrations with a wavefront
sensor and uses a wavefront corrector to compensate for the distortion.
MAOP, a patient looks through the phoropter viewport at a focusing
target. A light source, a superluminescent diode, is projected into
the patient’s eye and creates an image on the retina. A flip-in
mirror allows a computer to calculate the needed correction. By pushing
a button, the clinician can apply the computer-calculated prescription
and ask the patient if the image is clear.
splitter can be incorporated with the system to combine these two
steps. Then the patient can simultaneously view the focusing
target while the computer corrects the aberrations. The MEMS deformable
mirror uses a standard Shack–Hartmann wavefront corrector.
Light from a laser or superluminescent diode passes through the beam
splitter, flip-in mirror, adjustable lens, and telescopic lenses
and is then reflected off the corrector. Another set of telescopic
lenses directs the light through the eye and creates an image on
the retina. The wavefront sensor sends information to the computer
interface, telling the computer how to adjust the corrector.
is the first system to use the much smaller and less expensive MEMS
deformable mirror for adaptive optics and ophthalmic applications.
The wavefront sensor determines how much the wavefront is distorted
as it passes through the eye’s cornea and lens. A computer
uses this information to create an internal, three-dimensional (3D)
representation of the distorted wave. That 3D shape is then used
to instruct the 144 MEMS actuators to move to positions that will
minimize the distortion and “flatten” the wavefront.
Hope for Fighting Retinal Disease
Because MAOP features a modular design, it can be adapted for other
applications. Modules under construction will enable the system to
also perform retinal imaging. Traditional retinal imaging systems
cannot apply wavefront corrections and thus produce images with a
limited resolution, which hinders a doctor’s ability to diagnose
early-stage retinal disease. Adaptive optics systems, which can correct
wavefronts, produce far superior retinal images.
Higher-order aberrations, such as distorted vision from halos or
glare, increase with an individual’s age. Previous computer-calculated
methods do not correct for these problems and have not produced acceptable
results. MAOP not only measures and corrects these aberrations, but
it also can be used to evaluate eyesight under conditions that limit
vision, such as while driving at night.
Clinical studies at the University of Rochester, which were conducted
with earlier versions of MAOP, showed the benefits of correcting
higher-order aberrations. Patients with extremely poor vision—say
20:400, which is far below the normal 20:20 eyesight—reported
significant improvement when these aberrations were corrected. One
patient’s vision became
24 times better.
With MAOP, clinicians can train their staffs to operate a single
instrument with multiple functions and applications. The system can
also collect and store patient information—before and after
the correction is applied and the patient’s input is received—to
provide an eyesight history for help with later diagnosis. A MAOP
system outfitted with retinal imaging could be used to test new therapeutics
in clinical trials and provide objective measurements of a therapy’s
MAOP is the first system to measure higher-order aberrations in the
human eye, apply corrections, and immediately allow the patient to
see the results. It’s an innovative technology for early detection
and treatment of retinal diseases that cause vision loss and blindness.
And it will improve optical treatment for the millions of people
who depend on vision correction just to make it through the day.
Key Words: eyesight correction, microelectromechanical systems– (MEMS–)
based adaptive optics phoropter (MAOP), R&D 100 Award, retinal
Acknowledgments. In addition to the Livermore team, collaborators
included Ian Cox: Bausch & Lomb; Paul A. Bierden: Boston Micromachines
Corp.; Stephen Eisenbies, Steven Haney: Sandia National Laboratories;
David Williams: University of Rochester; and Dan Neal: Wavefront
For further information contact Scot Olivier (925) 423-6483
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