Cataracts are the most common aging change to affect the eyes. A cataract is a clouding of the lens of the eye. A cloudy lens blurs vision and reduces the amount of light entering the eye. A cataract change located in the center part of the lens can cause increased glare or dazzle. Visual acuity (sharpness of vision) may be severely affected, especially in rainy or foggy conditions or when driving at night. Cataract changes can even produce an extra image. All of these phenomena can affect day-to-day vision, and, of course, driving.
Fortunately, the surgery available to remove cataracts is highly advanced. The cataract is removed and an artificial lens, called an intraocular lens implant, can be inserted into the eye. If the eye is otherwise healthy, vision is restored.
Questions for drivers: Do headlights bother you? Have you noticed glare or dazzle on rainy or snowy days, or trouble with your night vision?
Macular degeneration is becoming more frequent as people live longer. The macula, a critical part of the retina, transforms light entering the eye into the images that transfer to the brain. With this disease, tissues in the retina degenerate. This aging change in the macula (the center of the retina) can lead to blurred vision, distortion of vision, a change in colour vision, and a central blind spot (scotoma).
If macular degeneration is complicated by hemorrhage (bleeding) or scar formation, a dense central blind spot can result. It can be large enough to stop a driver from seeing a pedestrian or a car in the line of vision.
Although new treatment possibilities exist, managing macular degeneration is very difficult. Sadly, if you have macular degeneration with scarring in both eyes, your vision does not overlap enough to allow you to continue to drive a car. It is an example of the importance of maintaining good general health in preserving the health of your eyes.
Questions for drivers: Have you noticed distortion or difficulty with the sharpness of your vision in the center of your field of vision?
Glaucoma is another disease that can interfere with your ability to drive. In this condition the optic nerve, which transfers images from eye to brain, is damaged by increased pressure inside the eye. For many years, glaucoma has been thought of as a silent thief, since it gradually reduces peripheral (side) vision. In driving, peripheral vision helps you to spot objects approaching from the side. It is especially important when passing through intersections. In end-stage glaucoma, only a small central island of vision remains - not enough to allow safe driving.
Unfortunately, glaucoma usually strikes silently and gradually. Many people are not aware of the condition until their visual field and optic nerve function are seriously damaged.
When it comes to glaucoma, an ounce of prevention is worth a pound of cure. Glaucoma testing involves measuring intraocular (inside the eye) pressure, and assessing the optic nerve and visual fields. Diagnosing and tracking people at higher risk for glaucoma can help save both their vision and potential accidents.
The many treatments for glaucoma include eye drops, oral medication, laser therapy and surgical procedures. They all work to lower the pressure in the eye and preserve vision.
Questions for drivers: Have you had your eyes tested for glaucoma?
Cerebral vascular accidents or strokes can also affect vision and the ability to drive. In a classic stroke, half of the area of the brain involved in vision is affected. As a result, half of the visual field in each eye is missing. The peripheral vision so important to driving is affected. Also, some people can have strokes that affect only their vision, and not their walking, talking, or other functions. Such strokes can steal the vision necessary to drive.
Preventing a stroke can be as simple as taking a low dose Aspirin™ (ASA) each day. It is very important that a stroke be treated quickly. Once damage is done to the part of the brain that serves the visual pathways, there is not much hope of significant recovery.
Questions for drivers: Have you discussed your risk for stroke with your doctor?
Vision requirements for driving follow some basic principles.
In some provinces in Canada, the medical examiner must notify motor vehicle licensing if someone does not meet the vision requirements. In other provinces, this is the individual’s responsibility.
Have a regular eye examination once you reach the age of 40. Your vision is one of your greatest assets, and necessary for safe driving.