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Sunday February 13, 12:54 pm Eastern Time
Wavefront measurements may replace eye charts
By Deena Beasley
LOS ANGELES, Feb 13 (Reuters) - The next time you go to the eye doctor, chances are a machine will be able to tell
whether you can make out ``T Z V E C L' before you even try to read the eye chart.
That's because the 100-year-old system used by ophthalmologists to find your eye prescription is likely to be replaced by technology -- invented by an astrophysicist
-- that can precisely measure how light waves are bent by each human eye.
Several companies are working on commercial ``wavefront' technology and at least one version, priced in the same $30,000-$50,000 range as other ophthalmic
diagnostic imaging systems, is expected on the market later this year.
Since the current method relies on the patient's judgment of whether a particular set of lenses results in better vision, access to more objective, scientific data will
give doctors much more accurate measurements, makers of the devices say.
In addition, the combination of wavefront measurements with increasingly popular vision correction surgery enables surgeons to directly input a map of the patient's
eye into the lasers used to reshape the cornea.
``Now, a bunch of lenses are dialed in front of your eye,' explained George Pettit, chief scientist at Autonomous Technology Inc., one of the companies
developing a wavefront device. ``But we have no way of measuring spherical aberrations, which are found for instance in some patients that have trouble seeing at
night.'
Whether traditional trial-lens devices end up in the dustbin of history will ultimately depend on how easy wavefront devices will be to use and how much they cost,
he added.
In the mid-1970s, Josef Bille, Ph.D., Director of the Institute of Applied Physics at the University of Heidelberg, developed ``wavefront technology' to correct for
the distortion to light rays, and the perception of shapes in space, caused by their passage through the earth's atmosphere.
Bille later co-founded 20/10 Perfect Vision to promote his technology for measuring the ability of the eye to bend, or refract, light so that an image is focused on the
retina.
Santa Clara, Calif.-based VISX Inc., (NasdaqNM:VISX - news) which makes lasers used to correct vison, has partnered with 20/10 Perfect Vision to develop a
commercial system that uses a wavefront sensor to track and measure the course of light rays through the eye and detect even the smallest aberrations at any point in
the optical system.
Bille is credited with reducing the size of the apparatus to the point where the benefits of the large-scale mirrors that were used in astronomy are instead captured on
a microchip, making the system more compact and affordable.
``Any ophthalmologist can use it,' Tom McKay, VISX marketing manager, said of the company's wavefront machine. ``This gives doctors a better refraction than
the current way of doing it.'
VISX, which has captured about 70 percent of the market for vision correction lasers, plans to have a stand-alone diagnostic wavefront device on the market by late
this year.
Demand in the United States for vision correction surgery such as Lasik -- in which the doctor slices a thin flap in the top of the cornea, lifts it, and uses a
low-temperature laser to sculpt the surface underneath -- is expected to climb 48 percent this year to 1.5 million procedures, according to industry consultant Market
Scope.
The VISX wavefront device will first be available as an add-on technology for doctors who use a VISX excimer laser, the company said.
The best use of the wavefront technology is for patients undergoing laser vision correction surgery, but it can also be used to better fit contact lenses and eyeglasses,
McKay said.
Current laser vision correction techniques reshape the cornea to a standard spherical shape based on the patient's manifest refraction, which is the trial lens
measurement used to prescribe contacts or glasses.
Autonomous, a subsidiary of eye laser maker Summit Technology Inc., (NasdaqNM:BEAM - news) also is working on a wavefront measuring device for eyecare
professionals that it calls CustomCornea.
Feasibility trials using the Autonomous device are now underway and the company expects to file for U.S. Food and Drug Administration approval this year, Pettit
said.
McKay at VISX noted that the CustomCornea device does not allow for patient feedback, while the VISX device incorporates a ``closed loop' system with an eye
chart that gives the patient the opportunity to verify whether they can see better.
``Frankly, we wanted this to be as objective and quantifiable as we could,' Pettit said. ``We didn't want any subjectivity in the measurement.'
In the clinical trials now under way, data from the wavefront sensing device, is loaded on a floppy disk that is then plugged into the laser machine in a room next
door, the scientist explained.
But like VISX, Autonomous also plans to sell a wavefront sensor separately from its laser systems, he said.
Once regulators approve it, eye surgery patients will eventually be offered the option of so-called ``custom ablation,' with surgeons able to map and sculpt the eye
so exactly that they can guarantee eyesight better than 20/20. |
