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Ronald D. Jesme
1000 Boone Avenue North, Suite 600
Golden Valley, MN 55427
Abstract:The Low Vision Enhancement System (LVES) is the first prosthetic device developed for people with chronic vision problems that cannot be corrected by lenses, medication or surgery. It is a portable electronic headset worn in front of the eyes like goggles. It makes use of remaining vision more effective by magnifying images and making differences between light and dark more dramatic. Many patients with visual acuity ranging between 20/100 to 20/800 can be helped with this system. The LVES consists of a binocular video display and three miniature cameras. Two cameras provide a three dimensional unmagnified wide angle view of the world, and one zoom camera allows magnification of images from three to ten times normal size. An additional flip-up close-focus lens allows magnification of up to 25 times for near viewing. A rechargeable battery is contained in the control unit that also houses image enhancement electronics and user controls. The user's view is equivalent to watching a 60 inch black and white video screen at a distance of 4 feet. The result is a virtual environment that is an enhanced version of the real environment. The portable LVES can aid low vision patients with reading, writing, work and daily living activities.
Introduction:The Visionics Corporation began operation in 1993 to develop and produce a video-based Low Vision Enhancement System (LVES) for use by individuals with vision impairments. The principle concept was to develop a system that would aid those with low vision by leveraging the capabilities of existing video technology. The primary components of the LVES include a head mounted display, head mounted cameras and separately housed image processing electronics. The system provides the user with a virtual window with an enhanced view of the environment. The concept and early development originated at John Hopkins University's Wilmer Ophalmological Institute. The U.S. Department of Veteran Affairs and NASA have collaborated with Wilmer during the reiterate and development program and provided substantial support for it.
The first production model of the LVES was developed by Visionics Corporation, and the first units were dispensed in June of 1994. In the year following more than 200 of these video-based systems have been successfully dispensed by some 30 clinics across North America. The LVES is a portable electronic headset worn over the eyes like goggles that makes more effective use of remaining vision. The LVES accomplishes this by magnifying images and making the differences between light and dark more dramatic. The LVES is battery powered and all parts can be worn by the user, making it extremely portable. Purely optical systems such as magnifying glasses and telescopes often are quite portable but they cannot actively enhance image contrast. LVES provides contrast enhancement, magnification and portability in a single device. The LVES is an individually-customized prosthetic: it allows users to augment their remaining vision electronically, substituting for their eyes' deficient functions. The development of this product was motivated by the desire for a single vision aid that could provide a significant performance improvement in daily living activities. Many persons with low vision require a variety of aids to perform the range of tasks encountered. Daily tasks include reading, recognizing faces, viewing distant objects and watching television. Users have found that using the versatile LVES can be more beneficial and convenient than carrying an array of magnifying glasses and telescopes. Many LVES users report they achieved their personal performance goals such as reading, gardening, recognizing faces and watching TV at levels not possible before.
A single Low Vision Enhancement System is composed of several electronic, optical and electro-optic components. Each system includes a binocular video display and three miniature cameras. Two cameras provide a three dimensional unmagnified wide angle view of the world. One camera is equipped with a zoom lens to allow magnification of images from three to ten times their normal size. An additional flip-up close- focus lens in front of the zoom lens enables magnification of up to 25 times for near viewing. The video image can be manipulated for maximum visibility with the control unit that also houses a rechargeable battery. The control unit also contains the image enhancement electronics and controls for zoom and focus functions. The video electronics provide automatic gain and brightness control, and can accept external video inputs. The binocular video display consists of two miniature cathode ray tubes (CRT) and a series of optical elements. The lenses and mirrors project the image present at the CRT face to the user's eyes. The lenses can be adjusted to the users optical prescription. The resulting view is equivalent to watching a 60 inch black and white video screen at a distance of 4 feet, providing a virtual window with an enhanced view of the real environment.
The LVES helps people with diverse visual impairments in a variety of ways -- more than might be expected of a small, portable device. Because the system uses video technology it can have automatic gain control (AGC), automatic brightness level (ALC), contrast enhancement, and both input and output video signals. AGC ensures that the image presented to the user has the maximum dynamic range, the range from bright to dark. This is important for maximum image detail, especially for those who have reduced contrast sensitivity. The contrast enhancement feature can further increase the gain (in contrast and brightness) to provide additional compensation for those with reduced contrast sensitivity.
ALC produces a constant scene brightness, independent of the environment's actual lighting conditions. This feature is especially appreciated by the users with eyes that cannot quickly adapt to variations in brightness such as people with pigmentosa or diabetic retinopathy. The LVES simplifies television viewing by becoming a kind of personal wide-angle television theater. The user has the choice of viewing television with system's cameras or connecting a video signal directly to the head mounted display. In the second mode the user can watch a TV or VCR program without regard to where the LVES's cameras are aimed. This eliminates the extra task of maintaining a television viewed by the cameras in the system's optical field of view and with it, any associated fatigue or strain.
The system's ability to present a three-dimensional view of the environment aids in spatial orientation. Motorized zoom and focusing functions provide sharp, variable magnification that can be conveniently adjusted. This collection of features provides dramatic benefits for a broad rang of vision impairments and in a broad range of viewing situations. The LVES is dispensed much as other prosthetics are prescribed and dispensed, by specially trained doctors and supporting technicians. People with vision correctable to a range from 20/100 to 20/800 routinely benefit from using the LVES. Persons with acuity as low as 20/1200 have expressed enthusiasm about the improvement the LVES provides. LVES candidates in this range receive a thorough low vision assessment to determine the appropriateness of the LVES for their vision impairment. If a person is likely to benefit from the LVES, a quickly- adjustable demonstration model of the LVES is prepared with his or her refractive correction. This demonstration unit allows LVES candidates to determine the benefits of the system for them when it is applied to "real-world" tasks that are important to them. If the benefits of the demonstration unit are sufficient, the LVES is prescribed, and a standard model system is customized for sale to the patient. This includes installing the refractive correction (both spherical and cylindrical), adjusting interpupillary distance and distance in front of the eyes, and locating head-mounting straps for proper alignment and secure fit.
After the LVES is dispensed, the new owner receives training in operating the system and applying it to everyday tasks. Although the present LVES has improved the quality of life for many users, many improvements and derivative models have been conceived. Concepts being considered include color systems, lighter and more compact systems that are cosmetically less obtrusive, and systems with configurable signal processing that can be tailored to compensate uniquely for the owner's impairment. Today's technology does permit the design of a LVES with more advanced characteristics, but its cost -- by present estimates -- would be out of reach for most people with low vision. Future technology will make a more advanced system affordable to typical vision impaired consumers, and provide more complete compensation of vision impairments.
Summary:The LVES has been accepted by the medical and user communities as an effective and credible device. Its dramatic effectiveness has been experienced by almost everyone who has viewed their environments through it. Many users enjoy the improved quality of life the LVES has provided in their daily activities. The LVES accomplishes its task through the use of many technologies, and will become more advanced as the latest technologies become affordable.
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