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Head-mounted devices improving, offering patients some replication of sight
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ATLANTA — Low vision patients who are severely impaired or have little success with conventional optical devices may achieve their visual goals with the latest electronic devices, specifically head-mounted displays, that are able to replicate some of their lost vision.
"These devices are not for the average low vision patient, but if someone wants to operate a computer and the level of vision is 20/100 or 20/1000, we turn to electronic devices," said Ned S. Witkin, OD, FAAO, director, Vision Rehabilitation Service at Emory University Eye Center here. "We assess patients and their level of vision and learn what it is they want to do."
Reading is generally an important goal for a low vision patient, Dr. Witkin said. "And in some cases, closed-circuit televisions (CCTVs) or video magnifiers work, but there isn't much out there except for head-mounted displays that allow patients to reach all of their goals."
Dr. Witkin supervises a tertiary low vision clinic. In addition to optometrists who evaluate patients and develop a protocol for low vision rehab, patient care is also coordinated with occupational therapists and the center for Rehabilitative Medicine.
Dr. Witkin said he dispenses a head-mounted low vision system for certain patients based on their visual goals and level of remaining vision. Both he and Scott Hearing, OD, FAAO, director of low vision services at the Stuart Eye Institute in Florida, have had success dispensing two currently available head-mounted devices.
Replicating lost vision
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According to Dr. Witkin, these two devices — the Low Vision Imaging System (LVIS) by Visionics and the V-max system by Enhanced Vision Systems — are able to replicate lost vision for some low vision patients.
Dr. Witkin said, "Each in a sense is able to replicate some lost vision. Each device uses a head-mounted display that is like a pair of goggles, and the patients looks into two very small television screens."
Dr. Witkin said the devices have a place in low vision rehabilitation. LVIS, a binocular de vice, has been available since September 1994, and late last year Visionics introduced its second head-mounted display system, called Aurora, which is a monocular device. Visionics has also introduced a third device, called Gemini, which is biocular.
LVIS has a camera that transmits a signal to two miniature television sets which projects an image through a series of lenses, beamsplitter, combiner and then directly into the exit pupil of each eye. LVIS is a monochrome display that offers magnification between 3X and 9X and a 50° field of view.
"LVIS's unique feature is its contrast enhancement circuit," said Dr. Wit kin, "and this appears to help people who have a loss of contrast sensitivity." LVIS has also been used as a CCTV.
The V-max system entered the market late last year. This system, Dr. Witkin said, offers patients full-color viewing by having them look at an image produced by one high resolution, auto focus, digital camera and presented on two liquid crystal display screens. The V-max range of magnification is between 0.8X and 20X. V-max also uses a technology called image stabilization, which helps images remain more stable and sharper at higher magnification.
With its camera mounted on top of a patient's head (LVIS mounts its cameras in front of the eyes), V-max converts into a traditional CCTV when clipped to a reading stand.
While neither device is a high-volume item, Dr. Witkin said, "For patients who need this technology, it's not so cost prohibitive that they can't afford it."
In 1996, his clinic was one of the largest dispensers of the LVIS system. Since he got the V-max system in his clinic 2 months ago, Dr. Witkin has dispensed two of the devices.
Choosing, then learning, a device
In his Florida clinic, Dr. Hearing estimates that half of his practice is low vision (80% adults and 20% children). Most of the adults suffer from age-related macular degeneration, he said, while the children have a range of anomalies, including retinoblastoma, ocular albinism, congenital optic nerve atrophy and Stargardt's disease.
Both systems have been designed for people of all ages, Dr. Hearing said. "The V-max offers color images but a smaller visual field and also doubles as a CCTV for those who are interested," he said. "The LVIS offers a larger visual field (50° versus 25°) with tremendous contrast enhancement, but a black-and-white image. Success with either system depends on the vision rehabilitation training program."
Dr. Hearing has dispensed nearly 35 LVIS systems since December 1995, and 8 V-max systems since February of this year. "I feel both products offer new solutions for our patients' problems, and this technology will lead to the Jordie 'glasses' of Star Trek fame in 5 years or less," he said.
One of Dr. Hearing's patients, a retired accountant who suffers from macular degeneration, said of the V-max system, "It has made my life worth living again."
Dr. Hearing said that once a head-mounted device has been dispensed, a patient will undergo a 90-day training period with an occupational therapist, an area critical to the patient's success. "Most doctors fail in low vision because they don't know how to properly train patients," he said. "Low vision is really a subspecialty, and this technology is not for every patient."
Dr. Witkin also stresses patient training, especially for head-mounted devices. "If the training is not adequate, the patient won't be successful, so we place a lot of emphasis on training and care after a protocol is established," he said. "We do task-specific training as well, and this continues until the patient is able to achieve his or her goals."
For Your Information:
- Scott Hearing, OD, FAAO, may be contacted at the Stuart Eye Institute, 2090 Southeast Ocean Blvd., Stuart, FL 34996; (561) 287-8777; fax: (561) 744-2498.
- Ned S. Witkin, OD, FAAO, may be contacted at Emory University Clinics, 1365-B Clifton Road NE, Suite B-5443, Atlanta, GA 30322; (404) 778-5820; fax: (404) 778-2244; e-mail: nwitkin@emory.edu.
- Neither Dr. Hearing nor Dr. Witkin has a direct financial interest in any of the products mentioned in this article, and neither is a paid consultant for any company mentioned.
- V-maxis available from Enhanced Vision Systems, 2134 Main Street, Ste. 187, Huntington Beach, CA 92648; (800) 440-9476; fax: (714) 374-1821.
- LVIS Aurora and Geminiare available from Visionics Corp., 1000 Boone Ave. North, Ste. 600, Minneapolis, MN 55427; (612) 544-4950; fax: (612) 544-4784.