Drivers Fitness Clear Vision
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 Drivers Fitness
Clear Vision The ability of the driver to have good vision is an important part of driver fitness. The SA Optometric Association provides insight pertaining to the requirement of clear vision on the web site www.saoa.co.za Safe driving involves: Visual acuity This is the ability to judge space and relative distance between objects or between an object and the vehicle. Depth perception depends on good binocular vision, essential for judging whether a car can be passed safely in the face of oncoming traffic and when moving from one lane to another among moving vehicles. This is the ability to focus and see clearly with both eyes, individually as well as together. With good acuity you will see detail very easily. In the case of drivers it is particularly vital in identifying road signs, cyclists, pedestrians and animals. Peripheral vision This is the ability to see over a wider area without moving either the eyes or the head, sometimes called "looking out of the corner of your eyes". It refers to your total field of vision. Depth perception Night vision This is the ability to see in the area of low illumination beyond your headlights, to see in the presence of the glare of oncoming headlights and to recover quickly from its effects. Night vision deteriorates with age and older drivers with reduced vision will need to exercise greater care when driving at dusk and at night and should have proper driving spectacles. WHY GOOD VISION IS NEEDED The eyes control most of your movements and decisions while driving. With good vision and visual comfort you can drive safely by maintaining concentration. Daylight vision problems are usually worse at night, increasing the risk in driving. Many motor vehicle accidents are caused by drivers’ poor vision. According to most parties involved in an accident, the other driver "must have been blind". Let’s look at some of the possible causes of these accidents:
TIPS FOR EASIER, SAFER DRIVING
[ Information provided by the SA Optometric Association ] Have your eyes examined by an optometrist once a year! Eye Diseases Eye Diseases that affect Drivers For most people, driving represents freedom, control and independence. Driving enables us to get to the places we want to go to at our own convenience. More importantly, to many others it represents a means of earning a living. Even though it seems so simple, driving is a complex skill. Your ability to drive safely can be affected by changes in your physical, emotional and mental condition. One of the physical changes that can occur happens with respect to vision. 90% of the information we use in driving comes through seeing therefore good vision is essential for road safety. If you can’t see properly, you can’t drive safely. Clear, comfortable vision will allow you to respond and react to road signs and other road users more quickly & accurately. Any eye diseases or conditions that affect your vision will in turn affect your ability to drive safely. Some of the leading causes of vision impairment in South Africa are cataracts, glaucoma, diabetic retinopathy and refractive errors. Cataracts A cataract is an opacity or “cloudiness” of the lens within the eye. When the lens becomes cloudy (much like the frosted glass in our bathroom windows), light cannot pass to the retina properly resulting in blurred vision. Cataracts occur in different stages. In its early stages it may be so small that it does not affect you vision and you may be able to drive safely for many years. With time the cataract will worsen making your vision dull and blurry. Having a cataract can make it harder for you to see the road, street signs, other cars, and pedestrians. You may find it more difficult to see things bright light and may have more trouble with glare from headlights. Colours may look more faded and your night vision may get worse. Some people also experience difficulty with judging distances and have double vision as the cataracts progress. 
Glaucoma Glaucoma is a condition in which the eye pressure becomes higher than the eye can tolerate. This is a painless condition that gradually damages the optic nerve. It causes “tunnel vision” and affects your peripheral or “side” vision. Depending on the stage of glaucoma, patients have dull vision and have difficulty reading road signs especially in low light conditions. 
This picture indicates typical “tunnel vision,” that occurs in glaucoma. Diabetic Retinopathy Diabetic retinopathy or diabetic eye disease, is damage to the retina of the eye from poorly controlled or long standing diabetes. This can also result in visual impairment and may lead to blindness if not detected and/or treated timeously. Some patients experience reduced peripheral vision, especially if laser treatment is needed. This affects the peripheral vision and makes driving (especially at night) unsafe. Patients with diabetic retinopathy may see “blotchy” and blurred images like these.  
Refractive Errors Refractive errors are the most common eye disorders. Most people have a refractive error, i.e. the eye has an “error” in its ability to focus light correctly. The term “refractive error” refers to myopia (shortsightedness), hyperopia (far/long-sightedness), astigmatism and presbyopia. Refractive errors are usually easily corrected with spectacles or contact lenses. Uncorrected refractive errors may make it more difficult to see traffic signs, pedestrians and other motorists as your ability to see at a distance is affected. This problem may be worse at twilight or at night. 
Figure 1. Indicates the vision that a persons with cataracts may experience – glare from headlights at night. Figure 2. Myopia or short-sightedness causes blurred distance vision Figure 3. Tunnel vision caused by loss of peripheral vision in glaucoma. How to maintain good driving vision
Human Error HUMAN ERROR AS MAJOR CAUSE OF ACCIDENTS Driver fitness as an essential element in road safety is highlighted by international studies on the cause of most accidents. Driver Fitness can be summarized as the physical and mental ability of the driver to enhance safe driving. In a comprehensive article on www.driveandstayalive.com it was pointed out that an international study concluded that human error was the sole cause in 57% of all accidents and was a contributing factor in over 90%. In contrast, only 2.4% were due solely to mechanical fault and only 4.7% were caused by environmental factors. Dr Green and Dr Senders discussed in an article titled "Human Error in Road Accidents" the reasons why humans make so many driving errors and they believe the answer is to be found in the inherent limitations of human information processing. Humans must rely on three fallible mental functions: perception, attention and memory. Research has also shown that accidents occur for one of three principle reasons. The first is perceptual error. Sometimes critical information was below the threshold for seeing - the light was too dim, the driver was blinded by glare, or the pedestrian's clothes had low contrast. In other cases, the driver made a perceptual misjudgment (a curve's radius or another car's speed or distance). The second, and far more common cause, is that the critical information was detectable but that the driver failed to attend/notice because his mental resources were focussed elsewhere. Often times, a driver will claim that s/he did not "see" a plainly visible pedestrian or car. This is entirely possible because much of our information processing occurs outside of awareness. Mack and and Rock (1998) have amazingly shown that we may be less likely to perceive an object if we are looking directly at it than if it falls outside the center of the visual field. This "inattentional blindness" phenomenon is doubtless the cause of many accidents. Lastly, the driver may correctly process the information but fail to choose the correct response ("I'm skidding, so I'll turn away from the skid") or make the correct decision yet fail to carry it out ("I meant to hit the break, but I hit the gas"). For response errors see "Medical Error and Mental Acts of God." In South Africa pedestrian fatalities have become a major contributor to road deaths. More than a third of childhood pedestrian deaths occurred over weekends and this has raised the question about drivers’ competence in terms of alertness, speeding, reaction time, and blood alcohol level. It is thus important that the Road Safety Strategy also focuses on the competence of our drivers to be alert and their ability both physically and mentally to make the right decision whilst driving. Importance Of Vision Road Safety And The Importance Of Clear Vision Clear vision means safer drivers and safer driving on our roads! It is estimated that approximately 90% of our daily activities require the use of our vision. When it comes to driving, vision is clearly the most important of our senses. When driving it is important to have clear comfortable vision. You need to be able to judge distances, read road signs and traffic lights and respond to changes in your environment quickly and efficiently. If you are not able to see well you will not be able to respond quickly when needed. This can be dangerous to both you and other road users. There are a number of eye conditions that can cause vision problems among drivers; however the most common reason for drivers and learner drivers failing the vision screening test is due to uncorrected refractive errors. What is a refractive error? A refractive error is defined as an imperfection in the focusing power of the eye, in which light rays are not brought into sharp focus on the retina. This results in blurred vision that can usually be corrected easily with spectacles or contact lenses. A refractive error is not a disease, merely an error. There four types of refractive errors namely
Myopia (short-sightedness) Most people with myopia complain of having difficulty seeing objects at a distance. Symptoms that drivers report include having difficulty seeing sign boards at a distance or reading the number plate of the vehicle in front of them. Some people find that they have to “squint” their eyes to see better. It is estimated that at least 20% of drivers are myopic. Myopia occurs when light rays come to a point of focus in front of the retina instead of precisely on it. 
Hyperopia (farsightedness) People with hyperopia tend to have more symptoms at near than at distance. They often complain of headaches, eyestrain, and tired eyes. They usually manage well enough during the day but find that they have difficulty seeing when driving at night. The vision problem occurs when the light rays come to a point of focus behind the retina instead of on it. 
Astigmatism Astigmatism often accompanies either short-sightedness or farsightedness. It is usually caused by an irregularly shaped cornea. The shape of an astigmatic cornea is often compared to that of a rugby ball, which has one shorter (steeper) curve and one longer curve. A normally spherical cornea is described as being shaped like a soccer ball. Due to the distorted surface there are two points of focus are formed instead of one, resulting in blurred vision. 
Presbyopia Presbyopia is an age-related change that occurs in the eyes focussing ability at near only. It usually affects people over the age of 40 but does not affect your vision for driving. If a vision problem is detected during the vision screening test it is important for you to have a comprehensive eye examination done. This is because some eye problems can result in permanent loss of if not detected and treated in time. A Comprehensive eye examination should consist of the following tests: Case History— You should be asked several questions relating to your general health, your family’s health and the problems that you are experiencing with your vision. It is important to report medical illness, surgery, injuries and any medication that you may be taking. Visual acuity test—This test measures what you are able to focus at and see clearly at various distances, with each eye individually and with both eyes together. This is vitally important for quick identification of road signs and obstacles on the road eg animals. Binocular vision (extra-ocular muscle alignment test)—These tests determine how your eyes work together. It is important in diagnosing squints, focusing problems etc. Depth Perception – this tests your ability to judge space and relative distance between objects eg, between an object and a vehicle. Visual field test —These tests check your “side vision” or peripheral vision. This is the ability to see and be aware of a wider field or area of vision around you while looking or focusing straight ahead. This is important in that it allows one to be aware of pedestrians, animals and cyclists on the sides of the road. Subjective Refraction—This is the process of determining the power of the lenses required to improve your vision. Slit-lamp exam—This instrument allows a magnified view of the eye. Tonometry—This is the measurement of your eye pressure. Ophthalmoscopy — This is an internal examination of the eye. It can be done through undilated pupils or more thoroughly, through dilated pupils Take care to remember that a quick or even free eye exam may not include all of the above and may be at the expense of loosing your vision if vision threatening conditions are not diagnosed. Medicine / Medication and Road Safety Medication and the Effect Thereof One of the greatest sciences today is that of medicine and it doesn’t matter what season of the year, the body might need it to help cure the cause and symptoms of illness. During the winter months a lot of us head of to our pharmacist in order to buy medication to relieve the symptoms of colds and flu. The summer months have their fair share of health problems as well with various allergies being amongst the main culprits. Indeed, we use medication for a variety of conditions. We take our medication in order to operate more efficiently, after all, most of us have to work for a living and have errands to run. Driving enables us to get to the places where we need to be. However, how many of us have given thought to the fact that the medication we are taking might be a source of danger to ourselves, to other road users and the property of others? Driving is a complex skill and requires mental alertness, clear vision, physical coordination and the ability to react appropriately, which can be affected by changes in our physical, emotional and mental condition. Most of us are aware of the dangers of driving under the influence of alcohol or illicit drugs, but certain types of medication produce effects that impair our ability to drive a vehicle safely. Drugs and Safe Driving According to the New Mexico Department of Health, certain drugs can interfere with factors that are essential for safe driving, such as:
The reactions caused by certain types of medication may include nausea, drowsiness, blurred vision, inability to think clearly, reduced coordination and diminished motor or judgment skills and can therefore impair your ability to drive. These medications include over-the-counter medication as well as scheduled medication, prescribed by the doctor. Care should be taken with medication developed to treat:
Many medications - particularly those that affect the central nervous system - can impair your ability to drive, for example: muscle relaxants, sedatives and tranquilizers, anticonvulsants, older generation antidepressants, such as tricyclics and central nervous stimulants. It remains in the body for several hours and will probably affect driving skills even on the next morning. Over-the-counter medications containing diphenhydramine, brompheniramine, or chlorpheniramine, such as those for allergies (antihistamines) are especially known to cause drowsiness. One study in the Annals of Internal Medicine suggested that a standard dose of the antihistamine had a greater negative effect on driving “coherence” than alcohol. Driving coherence is the ability to match the speed of the vehicle ahead to avoid accidents. This study also suggested that antihistamines and alcohol had similar effects on steering ability and the likelihood of crossing into another lane. Herbal remedies that interact with prescription or over-the-counter medications as well as medications administered to the eye, which can produce heightened light sensitivity, should also be avoided when driving. Yüklə 0,56 Mb. Dostları ilə paylaş:
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