sunglasses

Ordinary sunglasses. A serious limitation of ordinary sunglasses that is not obvious to the average user is that they degrade the vision in two ways. The obvious way is that they reduce the amount of light entering the eye, making everything darker and harder to see. The less obvious way is that any refractive error (nearsightedness, farsightedness, astigmatism) is made worse. This happens because the pupil becomes wider to compensate for the loss of light when the glasses are put on. And the wider the pupil, the more any refractive error contributes to poor vision. This is a simple thing for anyone to verify. Of course, one answer to this problem is to buy expensive prescription sunglasses. And new glasses must be purchased whenever there is a substantial change in the vision.
Traditional pinholes as sunglasses. Conventional, hole-type pinhole glasses also reduce the brightness of the sun, just like sunglasses. But they do so by creating a SMALLER pupil which improves the vision. This is also a simple thing to verify. Just put on a pair of pinholes on a sunny day and see how the brightness of the sun is reduced.
Modern pinholes as sunglasses. But the most extraordinary use of pinholes in place of ordinary sunglasses is with the modern pinhole glasses that look like sunglasses. In addition to the light reduction that is provided by the small holes, the lenses have built-in UV protection. So you get a sunglass effect and better vision at the same time with no need for expensive prescription sunglasses. These are really the ultimate in eyewear. They are inexpensive, stylish, improve visual acuity, function as sunglasses, can be used indoors or outdoors, and can last a lifetime. However, they should not be used for driving or any moving activity where good peripheral vision is required.
Ultraviolet protection. People who spend a lot of time in the sun should have glasses with ultraviolet protection in order to prevent damage to the lens and retina. Here is a comparison in order of increasing protection:
 Little protection: Prescription glasses made of CR-39 plastic, the most common lens material in the US. Such protection can be added, but only at additional cost. Not everyone wants to spend additional money on top of the high price they already pay for prescription glasses.
 Substantial protection:
1. Pinhole glasses with holes, since the total amount of light (including the UV portion of the spectrum) passing through the lens and reaching the retina is diminished.
2. High-index prescription lenses which have protection built in.
Since humans were never meant to totally avoid the UV spectrum in sunlight, the protection afforded by these two items may well be sufficient for most people.
 Full protection: Sunglasses and the modern pinhole glasses with smooth lenses: The lens material in both these products is normally treated to afford full UV protection.

KF-286 Pinhole as sunglasses

Sunglasses

sunglasses