As a minimum legal requirement to ensure safe driving, drivers should display visual acuity of 20/40 with or without corrective lenses. Restrictions generally apply to those with acuity between 20/41 and 20/70, limiting them to driving in daylight hours only.
A 120 degree wide field of view is the minimum legal requirement for peripheral vision in order to qualify for a license without restrictions (in some states the threshold is higher at 140 degrees). This is with or without corrective lenses.
If you are a wearer of telescopic lenses, a useful driving aid for sufferers of diminished visual acuity whose peripheral vision remains virtually intact, you will be subject to special requirements and additional testing.
Telescopic lens wearers must include the ability to locate stationary and moving objects within the telescopic field, and the ability to adjust successfully to changes in light levels, especially during inclement weather. Excessive contrast and glare sensitivity also compromises safe driving.
As a responsible driver, then, you should be aware of breaking the law if you fail to meet these visual standards every time you switch on your engine. In particular, if you do need to wear corrective lenses to meet the driving visual standard, it is vital you wear them at all times. It is a good idea to keep a spare pair of glasses in the auto so that you are never tempted to drive illegally without them.
Let’s now look more closely at drivers’ eyewaer as this aspect of vision care contributes significantly to safe driving. Here are some important guidelines:
* The current fashion is for narrower, thin-rimmed or rimless glasses. These are ideal for driving as they allow maximum peripheral vision (They are not so good, however, for cutting out the glare of reflected ultraviolet rays from snow and sand).
* At a reasonable cost, anti-reflective coatings can be applied to any lenses helping to reduce glare and enhance nighttime vision.
* Glasses with plastic lenses are safer and lighter. A plastic bridge helps cushion the nose if wearing metal frames.
* Keep a lens cloth in your auto along with your spare pair of glasses. Glasses and contact lenses should be kept scrupulously clean to ensure a clear field of vision.
* Wearers of contact lenses, and sufferers from hay fever, should also keep a spare pair of glasses in the auto. Switching to a pair of glasses when travelling long distances offers some respite for tired, watery eyes.
* If you need to wear prescription glasses to drive, never replace them with non-prescription sunglasses. It is illegal and does not make for safe driving. Instead, buy a pair of prescription sunglasses, or use clip-on lenses over your prescription lenses. A cautionary note: You should make sure that your clip-on lenses are suitable for plastic lenses.
* In adverse weather conditions where visability is poor, such as heavy rain or snow, never wear tinted glasses. This rule is equally applicable to tinted motorbike helmets.
Safe driving also means “vision care” or essential checks for your auto. Don’t restrict your view by putting non-essential stickers on the windows of your vehicle, or hanging objects such as dolls or dice where they might prove a distraction.
Keep your windscreen clean and free from scratches, and your lights adjusted to provide good illumination without causing glare. Protect your eyes from the glare of other vehicles by looking slightly to the left of oncoming traffic at night. Temporary blindness caused by glare can be particularly dangerous.
Safe driving means showing continuing responsibility. As we have seen, restrictions can apply to drivers where vision is impaired from cataracts, glaucoma, diabetes or any other relevant medical conditions which constitute a notifiable disability.
There are two key points to note here. First, if you are involved in an accident and are subsequently found to have an undeclared visual impairment, your insurance cover could be at risk.
Secondly, and more reassuringly, having a notifiable visual impairment does not automatically preclude your being allowed to drive. Limited-period licenses, issued to keep a regular check on your condition, and licenses restricting driving to daytime only, should be viewed as the ultimate safeguard of both vision care and safe driving.