Friday, 20 December 2013

Spectacles: Bringing the World into Focus

Despite the fairy tales, the size of our eyes has very little to do with how well we see. We don't need big eyes. But most of us will—or already do—need big lenses in front of them. In fact, half of all Americans wear glasses, and if you just look at the population aged 45 or older, the number jumps to 95 percent.

While this population includes a lot of different types of people, it's interesting to note that every president of the United States has worn glasses, all the way back to George Washington. Some presidents wore them only in the privacy of their office with the door closed. Others switched to contact lenses.

Even our two youngest presidents wore glasses. John Kennedy, who was elected president at age 43, wore reading glasses, although he rarely let himself be photographed wearing them. Theodore Roosevelt, who was elected vice-president at age 42 and became president shortly before his 43rd birthday (when President William McKinley was assassinated), was usually seen wearing his glasses.

The aging process that makes reading glasses necessary strikes everyone, regardless of race, creed, religion, prestige, or income. And it strikes us all at about the same time, too—in the early forties.

Once you get into your forties, the lenses of your eyes lose their flexibility and need outside help to focus for reading or close work. We'll look at the reasons why in a minute. But first let's take a brief look at the history of eyeglasses, which are also known as glasses, spectacles, specs, magnifiers, and even crutches for your eyes.

The Inventor:Leonardo Da Vinci 

As with so many other great ideas, Leonardo da Vinci is credited with first coming up with the concept of using magnifying lenses to see better. As technology improved, so did the idea, and the early hand-held magnifying lenses evolved into monocles, which could be held firmly in front of an eye by dint of a dutiful squint.

Since no one can squint all the time without developing a charley horse of the cheek, people kept their monocle on a ribbon pinned to their clothing so that it was always close at hand, even when not close at eye.

Monocles were followed by the lorgnette, two monocle lenses wired together and held to the face with a handle. In the 1600s, craftsmen started joining the two lenses together with a spring-type bridge that held the glasses on the nose.

In 1728 or thereabouts, a London optician named Edward Scarlett invented eyeglasses with temple pieces. But they weren't designed to hang on the ears. Instead they stayed in place by gripping the head in a migrainelike embrace.

It's worth remembering that patent laws weren't very rigid 250 years ago, and it's hard to prove that any one person was the first to do anything. The odds are that reading glasses—like the wheel, shoes, and rock and roll—were an idea whose time had come. They were probably developed by a number of different clever people working independently.

Take, for example, the case of bifocals. Tradition states that Benjamin Franklin should get the credit for that one, because he crafted glasses that combined an upper lens for distance vision and a lower one for near vision. Franklin first wrote of his invention in 1784. But London opticians had been experimenting with the idea for more than 20 years by that time, and other people had been writing about the concept since at least 1716.

But regardless of who first actually made that optical breakthrough or any of the others, those early glasses were designed to do the same thing Leonardo da Vinci's magnifying lenses were designed to do centuries earlier—correct a few of nature's mistakes. 

Five Myths about Glasses

There are myths about four-leaf clovers, dogs named Rover, golden jars, and shooting stars, so, of course, there are myths about glasses, too. And many of them make as much sense as the one about four-leaf clovers bringing luck. Here are five of them:
  1. Wearing glasses will strengthen your eyes. Glasses don't change your eyes at all. What they do affect is your vision, by giving your brain a clearer image of what your eyes see.
  2. Wearing glasses will weaken your eyes. See myth number 1.
  3. Wearing glasses will make you "addicted" to wearing glasses. The only habit that wearing glasses develops is the habit of actually seeing what's going on around you—and seeing it clearly and distinctly
  4. If you have a lot of headaches, you need glasses. If you have a lot of headaches, it means that you have a lot of headaches. Because the vast majority of headaches are tension or stress-related, the odds are you are under a lot of stress. A small number of headaches can be classified as migraine headaches. High blood pressure, sinus infections, allergies, and tumors can also cause headaches. Rarely will people develop headaches because they need glasses. Those who do are usually farsighted and develop headaches when they read for a long time without wearing glasses. When they stop reading or start using glasses, the headaches will usually disappear.
  5. Glasses make you smarter. Obviously a conspiracy started by the people who manufacture glasses, this one is based on appearances. For reasons better dealt with by practitioners of cultural anthropology than of ophthalmology, we tend to think that people who wear glasses look smarter than people who don't. One possible reason is that we associate glasses with people who have weak eyes because they read so much (see myth number 2). But wearing glasses can also make you appear smarter by giving you more time to think. Ask people who wear glasses a hard question and they will very likely take the glasses off and clean them before answering you. They aren't cleaning their glasses because the glasses need cleaning, or to see the problem—or you—more clearly. They're doing it to give themselves a few extra seconds to think of an answer, time they wouldn't have if they didn't find something to do with their hands while they were thinking.
Ancient Tibetans wove fine horsehair into a kind of sun visor. And more than 2,000 years ago, the Chinese wore tinted lenses because of the good luck they supposedly brought—and the bad luck they supposedly prevented. Chinese judges, for example, wore smoked-glass lenses to conceal their thoughts from defendants.

Tinted lenses were worn in the United States in the early 1800s, but they didn't really take off until the first planes did. It was in the 1920s that the U.S. Army Air Corps started looking seriously at sunglasses as a way to help fliers cope with high-altitude glare. The sunglasses market has been flying high ever since.

While many people look at sunglasses as a fashion accessory, they do also provide important visual comfort and protection by cutting down on the amount of visible light, glare, and ultraviolet (UV) radiation that reaches the eyes. The amount of light that does get through is determined by the "transmission factor" of the sunglasses.

Generally speaking, no more than 30 percent of outdoor bright sunlight should be transmitted to the eyes. But if you are at the beach or on the ski slopes, where the sunlight is brighter and there is a high glare factor, a transmission factor of just 10 to 15 percent may be preferable. Manufacturers often attach a tag to their sunglasses listing the transmission factor.
Depending on what you are going to be doing, you might prefer one of the following types of sunglasses:
  • Gradient density sunglasses are dark at the top, tapering to clear at the bottom.
  • Double-gradient density sunglasses are dark at the top and at the bottom and lighter in the center. They are especially useful for driving, boating, or any other situation where there is a great deal of overhead light and low-level glare.
  • Reflective sunglasses have a thin metallic coating that reduces the amount of light that reaches the eyes by reflecting it away.
  • Polarizing lenses eliminate vertical glare. They are very effective and often very comfortable.
  • UV lenses filter out ultraviolet rays.
  • Photochromic lenses adjust to the amount of light hitting them by automatically becoming darker in bright sunlight and turning clear again when the light dims. While many people are happy with automatic sunglasses, others find the process bothersome and too slow.
More and more researchers are tying excessive UV exposure to a number of serious eye problems such as cataracts and macular degeneration. While more work needs to be done to prove this connection, if it is true, glasses that screen out UV light may help slow down these sight-threatening conditions.
In the meantime, what should you do about UV light?
  • Be aware that a connection may very well exist. It hasn't been proved yet, but it hasn't been disproved, either. Play it safe, but don't let it drive you crazy with worry.
  • Be aware that there are a lot of promoters out there trying to put the fear of God into all of us about the disastrous effects of UV light. And once they have us thoroughly cowed, they pull out their complete line of UV glasses.
  • Take some reasonable precautions. Try not to face directly into the sun; wear sunglasses if you spend a lot of time in bright sunlight.
Some research is being done now with sun-screening eye-drops, which would block out potentially harmful UV rays. The drops would last for several hours and would be reapplied as needed. But even if they do work, they won't reduce glare or brightness. Sunglasses will still be around.

Just as sunglasses come in different styles, they also come in different colors. But no matter what the current fashion gurus might dictate, you don't want to look out at the world through rose-colored glasses—or pink, blue, or purple ones.

Neutral gray or "smoke" is the best color. It gives the best color perception and the least distortion. It is also the most difficult tint to produce, and as a result, it is only available in better-quality, more expensive sunglasses.

Green and brown-tinted lenses are also good choices, but forget the silly ones designed by people who think color-coordinating your sunglasses and your shoelaces makes an important fashion statement. Pink, blue, purple, orange, rose, yellow, striped, and polka-dot sunglass lenses look better on a store dummy than they do on you—and are about as useful.