Presentation on theme: "Driving and Visual Impairment. Title II of the Americans with Disabilities Act "No qualified individual with a disability shall, on the basis of disability,"— Presentation transcript:
Driving and Visual Impairment
Title II of the Americans with Disabilities Act "No qualified individual with a disability shall, on the basis of disability, be excluded from participation in or be denied the benefits of the services, programs, or activities of a public entity, or be subjected to discrimination by any public entity."
National Eye Institute With the aging population, the number of Americans with major eye disease is increasing and vision loss is becoming a major public health problem. Visual Impairment affects 3.3 million Americans over age 40. There will be 5.5 million visually impaired by The leading cause of visual impairment in white Americans is macular degeneration, 54%. Leading cause of visual impairment in African Americans is cataracts and glaucoma. The leading cause of visual impairment in Hispanics is glaucoma. One in 12 people with diabetes age 40 and older has vision threatening diabetic retinopathy.
Visual Impairment, Driving & Bioptic Telescopes Is this really a good Idea? Driving is not a right but a privilege. Safety of both the driver and the public must be the overriding consideration. A complex and controversial issue.
What Visual Acuity is Necessary for Safe Driving The recommendation for the minimum standard of 20/40 acuity for driving was made by the AMAs Section on Ophthalmology in Untrue that street signs are calibrated for 20/40 vision. Signs vary greatly. A 4 foot child at ¼ mile subtends a visual angle greater than 20/200. Kekkeher 1979 The 20/40 requirement is arbitrary and is not based on actual visual acuity demands while driving. Fonda & Wess
Feinbloom (1977) blurred the vision of 12 normally sighted drivers with +3.00D lenses and had them drive in various traffic and weather conditions. Pedestrians, animals, bicyclists and traffic lights reported visible. The only problem encountered was the inability to read signs.
A person with 20/200 daytime visual acuity, traveling at 40 mph can recognize a stop sign in sufficient time to react safely. Fonda 1989
Burg Study, 1967 Study conducted on 17,500 California Drivers. The relationship between driving record and corrected vision was quite small and in the opposite direction from what would be expected. Good Vision was associated with a poorer driving record. Since that study, there have been numerous studies with similar results. The correlation between accidents and visual acuity has been shown to be less that 1%.
Why is there no correlation between Visual acuity and crash rate Are current standards of vision screening inadequate? Are they measuring the wrong thing? Or, are they so successful (sufficiently restrictive) that they have effectively eliminated any accidents that could be explained by reference to vision? We will never know the answer to these questions unless we raise the visual acuity standard. Current standards may unnecessarily restrict drivers.
Driving & Other Disabilities Drivers licenses are issued to a wide range of physically challenged individuals but visually impaired individuals are frequently denied licensure. Studies comparing the driving records of various groups of handicapped drivers consistently report a favorable ranking of visually impaired drivers. Appel & Brilliant 1990 The Texas Medical Advisory Board revealed ratios of 8.5% for drivers with neurologic impairment, 5.63% for drivers with cardiovascular impairments and 4.86% for drivers with visual impairment. Lippmann 1979
Most low vision driving is done by normally sighted individuals driving under poor conditions such as after dark and in snow and rain. A normally sighted individual driving at night with high beams only has an effective visual field of 40 degrees. Proper defensive driving strategies minimize the risk of accidents even under conditions with extremely poor visibility.
Drivers License Requirements Visual screening standards are set by each states legislature and are implemented by the Department of Motor Vehicles. Drivers license requirements have been shown that they are not a good predictor of driving performance. After several decades of research, there is very little empirical evidence concerning the minimum visual requirements for driving. Vary from state to state, especially with how they deal with visually impaired drivers.
In many cases people drive legally and safely with visual impairment. Denying a person a drivers license needs to be based on empirically justified standards. New types of studies are needed to determine if vision standards can be relaxed without endangering public safety. Licensing standards need to be uniform across the country. A selection process is needed to eliminate those individuals who are incapable of visually adapting to the demands of driving.
The loss of a drivers license, or the inability to obtain a drivers license is a much greater issue than just loosing the ability to drive. Loss of independence Self worth is tied to the ability to drive Decreased quality of life Social isolation Depression Limitations in vocational options
Problems Associated with Driving with Bioptic Telescope Most bioptic drivers receive little or no instruction on how to use their bioptic telescopes for driving. Small field of view when using telescopes. Telescope induced ring scotomas. Jack-in-the box effect. Vibration of image while driving.
Two Types of Drivers Licenses Exist for Persons with Visual Impairment Restricted license Regulations vary from state to state. Corrected visual acuity may be 20/40 to 20/120 in the better eye. Other possible restrictions: daylight only, limited distance, limited purpose or no freeway driving. ) Bioptic Telescopic System License Regulations vary from state to state. Vision through the telescope may be 20/40 to 20/ 70. Other possible restrictions: daylight only, limited distance, limited purpose or no freeway driving.
In many states the person at the DMV counter does not have the final word regarding a persons ability to drive. The vision test can often be taken at an eye doctors office.
Bioptic Telescopes A Bioptic is a lens system with a telescope attached to a pair of glasses, usually above one's normal line of sight. Bioptic does not imply two eyes, it means that the wearer has two optical systems, the spectacle lens (carrier) and the telescope. Bioptic Telescopes for driving were first implemented in 1969.
Spectacle mounted telescopes vary in power from 1.7X to 10X. When viewing through the telescope only a small area is seen, 4 – 18 degrees. The stronger the telescope, the smaller the field of view. The telescope becomes increasingly harder to use with increasing power. Smallest effective power telescope should be used. Some states restrict the power that can be used.
There are two basic types of telescopes Galilean Telescope Smaller Lighter Smaller field of view Less expensive Poorer image quality Rarely used above 3X power Brighter image due to only 4 lens surfaces Keplarian Telescope Longer Heavier Larger field of view More expensive Good quality image Smaller ring scotoma Spectacle mounted up to 10X power Less bright image due to 10 lens surfaces
Comparing Designs For Vision 3X Keplarian TS (14 degree) to 3X Galilean TS (8 degree)
Driving with Bioptic Telescopes A telescope helps the visually impaired driver see detail such as signs and traffic signals. 95% of the time, the wearer drives looking through the carrier lens. When extra magnification is needed, the driver will briefly drop his head to view through the telescope. The driver views through the telescope briefly, one or two seconds at a time.
The bioptic drivers use of the telescope can be likened to the normally sighted drivers use of the rear and side mirrors. It is used as a spotting tool. Although bioptic telescopes can be placed binocularly, most bioptic telescopes used for driving are placed only over the better seeing eye. This leaves the field of the other eye unobstructed.
Ocutech 3X Mini - The telescope is placed above the line-of-sight and angled upward
Conforma BITA The BITA (Bi-level Telemicroscopic Apparatus 3/8 & ½ diameter 2.5X, 3.0X, 3.3X, 4.0X, 5.0X, 6.0X
The carrier lens can contain the patients distance prescription. It can also contain a tint or filter. The patients prescription can also be placed in the ocular lens of many telescopes. The telescope can be focusable or non- focusable. Focusable telescopes allow for better fine tuning of vision. The telescopes are not focused while driving.
Spectacle & Telescope Filters A removable cap with a filter can be place on the objective end of many telescopes. Although Corning CPF Lenses cannot be used to mount telescopes because they are glass, Transitions lenses can be tinted to match the CPF filters and can be drilled to mount the telescope. Tints can be added to side shields. Do not use frames with thick temples as they may block side vision.
Other Forms of Glare Control Driver can wear a baseball cap and move the visor on his head right, left or straight ahead depending on where glare is coming from. Filters can be added to car visors. Filters can be attached to the rear view mirror to block glare when looking into the mirror.
Seeing the Dashboard Most users of telescopes cannot see the dashboard. Focusing the telescope while driving is not practical or safe. Memorize the position of numbers prior to driving. Mark the cover to indicate various speeds. Purchase a car with a digital speedometer. Page magnifier added to dashboard cover. Ocutech Autofocus Telescope – not a good solution.
Candidates for Bioptic Driving Low vision individuals with visual acuity 20/200 or better. No peripheral field defects. Stable ocular conditions, usually congenital. Albinism, aniridia, congenital nystagmus Some macular degeneration patients may be good candidates depending on the stability of the disease and eccentric viewing skills.
Success with optical magnification at near is a good predictor of success using a bioptic telescope. Relatively good measured distance visual acuity does not always ensure success with telescopes. Driver must be responsible and have good judgment. Drivers should be assessed based on their individual cases and not on just current state regulations.
Low vision drivers have to demonstrate that they meet the vision requirements for driving. They must also demonstrate that they can perform all regular driving tasks such as speed control, merging, driving in traffic and effective use of mirrors.
Visual Function Is Not Simply A Function of Visual Acuity Visual Field Color Vision Decreased Contrast Sensitivity Glare Sensitivity Cognition Useful Field of View/ Dynamic Vision
Visual Field Peripheral vision helps the driver notice when a child is chasing a ball before he runs in the street. Peripheral vision lets you know when a car is overtaking you when you change a lane. 36 States have visual field requirements, 20 – 150 degrees. There is a strong correlation between crash rate and visual field. No consensus as to the size of the visual field needed for safe driving. While prisms can increase a persons awareness of missing visual field, they do not actually increase the visual field. They are not usually allowed as a drivers tool.
Color Vision No correlation between poor color vision and driving safety. Some states test for color vision because they feel it may be useful in identifying traffic signals.
Decreased Contrast Sensitivity Contrast sensitivity tests measure the ability to detect low contrast stripes, letters or objects. A better predictor of actual visual acuity. Good contrast sense is needed to see a dark car on a dark road or a white car in the snow. Studies show that drivers with decreased contrast sensitivity have higher involvement in at-fault car crashes. Wood & Troutbeck 1992 Not currently tested in any state.
Cognition & Motor Skills Population is aging. The largest group of people who will become candidates for bioptic licenses will be elderly adults with acquired vision loss. Since 1995 highway deaths in the over 65 age group has increased 15%, under 65 there has been a 3% decrease. There is a strong correlation between decreased cognitive skills and crash rate. 85 year and older have lowest accident rate. However, accidents/miles driven rate is 2X higher than the year old male.
Glare Sensitivity A problem for many elderly drivers and many individuals with visual impairment. Can lead to hazardous situations while driving. Use correct glare control filters. Clean windshields. The states do not mandate tests to evaluate glare, either from sun or other cars at night.
Useful Field of View or Dynamic Vision Test of visual attention. The test measures a subjects ability to correctly identify central targets while simultaneously having to localize peripheral field targets, with and without the presence of distracting targets. For elderly drivers, there is a 50% correlation between poor results on this test and at-fault crash involvement. Visual attention may serve as a better screening method compared with current screening tests. Owsley and Ball 1993 No state is using this test as a screening tool.
Who Should Be Involved? Eye doctor: determines what is needed medically, surgically and optically. Also acts as an advisor to the patient. Patient must be seen as a whole, VA is only one factor. Eye doctors make statements regarding a patients visual acuity and visual field, the motor vehicle department further evaluates the patients ability to drive. Vision rehabilitation specialists: eye doctor, low vision therapist, mobility instructor and/or occupational therapist specializing in LV rehabilitation develop a rehabilitation and training program.
Instructor for in-the-classroom drivers training program. Driver Educator: trains the driver to compensate for visual deficiencies to maximize safety behind the wheel. Certified Driving Rehabilitation Specialist who is certified in Bioptic Driver Training. The on-the-road training uses a specially equipped duel brake controlled vehicle.
Drivers Training Program The bioptic telescope alone does not make a person safe. Training is necessary. The potential driver must first learn to use the telescope at home. Learn to spot stationary targets while stationary. Learn to spot and track moving targets while stationary. Learn to spot moving targets while moving. First task is accuracy, second task is speed. The spotting speed should be accomplished within one-half second on a consistent basis.
In-Car Training as Passenger Training first as a passenger. Spotting, scanning and tracking mastered before actual drivers training. Scanning This allows the driver to see traffic conditions at a distance. Spotting Must learn to find a target immediately without searching. Object is localized through the carrier lens and then identified through the telescope.
In-car Training as Driver Learn scanning movements through mirrors to keep track of traffic on the side and behind. Drive all types of road conditions that are allowed by the drivers license: residential streets, major traffic artery, downtown rush-hour, highways and freeways. Driver must master reading signs and scanning road conditions ahead, using mirrors all while staying alert to pedestrians, bicyclists, pets and children.
Difficulty Driving on the Street Depends on Three Variables Object Vision: Objects dont always have to be identified to drive safely. Driver needs to know something is there. Detail vision is needed to see street signs. Visual Clutter: Unimportant objects such as telephone poles and advertising signs that interfere with the objects that need to be identified. Speed: To control both object vision and visual clutter the driver may need to reduce speed.
Statistics on Bioptic Driving Many people drive legally and safely with a visual impairment 39 states allow the use of bioptic telescopes for driving. Six of these states, the vision requirement through the carrier lens is the same as regular drivers.
Low Vision Driver Education Training Charles Huss. C.O.M.S., year study of visually impaired bioptic drivers. Multidisciplinary group of researchers: driver rehabilitation specialist, low vision optometrist, O&M specialist, audiologist and occupational therapist. 47 drivers with VA between 20/50 and 20/200, stable eye condition, full visual fields and 20/40 vision using the bioptic telescope. After training, 31 drivers became legally licensed to drive. 6-8 week low vision driver education training program 30 hours of classroom education 40 hours as a passenger training with and without telescope 50 hours behind-the-wheel training in all driving type situations
Survey of Drivers after 10 years Accident and violation-free driving records by 14 of 31 graduates. At least one accident by 12 graduates, (18 for total group). In 10 accidents drivers were not at fault. 7 minor traffic violation by 7 graduates, 8 total. Twice the number at-fault accidents and traffic violations by those falling in the 20/50 – 20/70 category versus the 20/80 – 20/200 category. Nearly 100% educational or vocational placement.
Conclusion of Study Individuals who completed low vision driver education satisfactorily performed at a level comparable to their normally sighted counterparts in terms of basic visual skills and demonstrated above average skills in vehicle handling and ability to react to traffic hazards.
Good Resources for information on Bioptic Driving www. BiopticDriving.org