The material below is drawn from my tried-and-true resource, David Hough, author of “Proficient Motorcycling.” Having recently passed yet another birthday (how can that be?) I was sulking about how I need to increase the prescription on my reading glasses – again. David writes about how critical eyesight is for motorcyclists, with special notes about how aging impacts our vision in unexpected ways.
Human eyes have some interesting characteristics that can get us in trouble, and we’re not talking about winking at the Sheriff’s daughter. Be aware that every eye has a small blind spot, usually off to one side of center. It’s something that can be measured during a good eye exam. Fortunately, the blind spot of our left eye doesn’t overlap the blind spot of our right eye, so both eyes together can cover the whole field of vision. But, consider that a bug splat or a scratched face shield in a critical area can totally blot out a portion of the view. That’s one good reason to keep your head and eyes moving, and your face shield clean.
Our vision also tends to fade as we get older. One common problem is floaters that drift around on the surface of the cornea and interfere with clear vision. As the years go by we discover that our reading glasses don’t work so well any more, or we can’t read our motorcycle instruments so well. If that’s the case for you, consider a pair of glasses with a middle distance correction for riding.
One other odd characteristic of human eyes is that color relates to distance perception. It is more difficult to judge the distance to a red light. In other words, you might be able to accurately judge the distance from you to a green light, but not to a red light. Since tail lights are red, it pays to occasionally count out your following distance, rather than assuming your eyes are giving are giving you an accurate reading of distance. At night you should adjust your following distance to no closer than four seconds.
The eye can adjust to bright daylight by closing down the iris. But the vision receptors in the back of the eye also chemically adjust to the average light intensity. And that chemical change takes a while. Our eyes can’t instantly adjust as we go from bright light to darkness. This is most obvious when walking out of a brightly lit room into the dark. Experienced night riders wait a few minutes before riding away.
Consider what happens when someone takes a flash photo of you while you’re staring at the cam-era. The flash of bright light overwhelms vision for three or four seconds. The same thing happens when you ride from bright daylight into an unlit tunnel or at night when a car goes by in the opposite lane. What do you do when you’re cruising down a narrow road and an oncoming vehicle approaches with its lights blazing? As the car approaches, your eyes will adjust to the higher light level, and then when the car passes, it takes several seconds to adjust back to low light again. In the meantime, you’re effectively blind.
The trick is to avoid focusing on the bright lights. If you stare at the oncoming lights, you’ll be temporarily blinded. Instead, as the other car approaches, temporarily shift your focus to the white line on the right shoulder of the road. The vision receptors in your peripheral vision may be temporarily over-whelmed, but your important central vision is saved for the dark road you need to see after the car passes. If you haven’t tried this before, it may be unnerving to look away from that other vehicle coming at you, but your peripheral vision is able to track movement and lane position, and your focus on the fog line helps you maintain your lane position. It is more important to be able to see that narrow bridge that is coming up next in the critical moments after the car goes by.