A story in the New York Times about aging eyes opened mine this morning.

It says, right there in black and white, that, "the typical 50-year-old driver needs twice as much light to see as well after dark as a 30-year-old."

But ... but ...

My vision has actually improved as I've aged. Really. The correction I need gets weaker every year. Seems my life-long affliction with myopia has run into age-related far-sightedness and given me better eyesight than I've ever have.

Of course, this is most likely not destined to continue indefinitely. At some point, I'll find my arms too short and still won't be able to have anything in the distance look more than a blur. That's an age thing.

There are a number of those age things, as the list doesn't end with short arms and cataracts.

In dim light or darkness, eyes adapt by widening the pupils to let in as much light as possible. The iris (the colored part of the eye surrounding the pupil) contains tiny muscles that control the size of the pupil. As you get older, these muscles (like most in the body) weaken and do not respond as well to the need to let in more light. The result is a small pupil when you try to see in poor light. It’s as if your eyes were still young but you were wearing sunglasses at night.

(Why does Maynard G. Krebbs come to mind? Wow! I'm really aging myself with that one! Does anyone else remember Maynard G. Krebbs?)

Anyway ...

I was surprised to learn that one of the worst things for night vision is sunlight. In fact, the number one recommendation for hanging on to your ability to see in low light is to protect your eyes during the day. Seems that bright sunlight actually bleaches the photoreceptors in the eye.

There are other causes of visual aging, of course.

Although there are neural losses, the major decline is due to changes in the eye's optics. First, the lens becomes yellower, making discrimination of blue colors more difficult. More importantly, less light entering the eye reaches the photoreceptors. One problem is that the lens and other optical media become opaque. Further, the pupil shrinks, allowing less light to enter the eye.

Because of these factors, by age 60 you have only 33% of the light reaching where it counts than you did at 20. By the late 70s, it's less than 12%.

Continued ...