PINHOLE GLASSES

PINHOLE GLASSES

Modern pinholes that look like sunglasses.
They're a whole new design of pinhole glasses!
To see these and many other styles of pinhole glasses,
visit CaribbeanEyes.

How pinholes function. Pinhole glasses (also known as stenopeic glasses from the Greek words for "little opening") are not made of glass at all but of an opaque substance such as metal or plastic. The user looks through any of the many small holes in the material. These holes have the effect of reducing the width of the bundle of diverging rays (called a "pencil of light") coming from each point on the viewed object. Normally, the full opening of the pupil admits light. It is the improper bending of the outermost rays in that pencil of light which causes refractive errors such as myopia, hyperopia (farsightedness), presbyopia (diminished focusing range with age) and astigmatism to be noticeable. Pinholes can bring about clearer vision in all these conditions. By blocking these peripheral rays, and only letting into the eye those rays which pass through the central portion of the pupil, any refractive error in the lens or cornea is not noticed as much. The pupil may be wide open, but only the central portion is receiving light. The improvement in visual acuity can be striking.

Look at this drawing of a myopic eye with a pinhole lens in front of it. You will see that the eye does not need to deal with the rays that would need the most bending since they are blocked by the lens. It is said that Scheiner first described this effect in 1573. Those who are familiar with cameras will recognize that this is the same principle used to increase the depth of focus by decreasing the aperture. Pinhole cameras also operate by this principle.

Pinhole lens

An easy way to demonstrate this is to make a fist and put it up to one eye while closing the other eye. Open the fist just enough to create a small hole to look through. If you have a refractive error, you should see more clearly this way. This same improvement in the vision takes place when someone squints to see more clearly. The upper and lower eyelids cut off the rays that would normally enter the top and bottom of the pupil and the vision improves somewhat. Since there is no similar way to cut off rays entering the sides of the pupil, these rays still contribute to the blurred vision. Looking through pinhole glasses instead of squinting cuts off the peripheral rays from all sides. Since the glasses are so close to the eye, the material between the holes is greatly out of focus and is not as disturbing as one might think. After a period of getting used to the glasses, the brain tends to ignore the presence of the material.

Also of interest is that the farther away the viewed object is, the less the pinholes are noticed. The honeycomb effect of the holes is more noticeable when viewing a book held close to the eyes, because the eyes are focused just a short distance in front of the glasses. When looking at a distant TV, however, the holes are hardly visible at all since the eyes are focused much farther away. Also, because of the distance, you can view the entire TV screen through one hole, an obvious benefit.

Looking through the teeth of a comb held in front of the eyes is another way to simulate the pinhole effect. The native people of Alaska have long used this principle by wearing glasses with narrow slits to look through, thus blocking out much of the glare from the sunshine reflecting off the snow and ice. Anyone who remains in this environment for long periods during the summer without protection can suffer from snow blindness. This painful condition forces the person to discontinue the use of the eyes until healing can take place. This is nature's way of protecting the eyes from permanent damage.

Some advantages that pinholes have over prescription glasses:

As we get into our 40's and 50's and presbyopia (inability to focus close) develops, pinholes provide a simple and inexpensive solution for reading or other close work.
Bifocals or trifocals are designed to provide a clear image only at fixed distances. Pinholes provide an improved image at ALL distances. In many applications, such as alternating between watching TV and reading, they can easily take the place of those very expensive prescription lenses that are so lucrative for the anti-consumer eye doctor/optical industry alliance.
Multi-focal lenses provide a continuously variable curve that is supposed to give good vision at all distances. In reality, the distortion on either side of the center line is considerable and often too great for comfortable use. Pinholes eliminate this problem.
There is no need to continually throw away old glasses and buy new, stronger ones. Unless the pinholes break, they can be used an entire lifetime.
While pinholes are not as cheap as off-the-rack reading glasses, they are considerably cheaper than individual prescription glasses. For example, a person who is a little nearsighted but only needs clear distant vision for occasional TV viewing would find pinholes a cheaper solution than prescription glasses.
Off-the-rack reading glasses have the same lens power in each lens. Some people find these cheap glasses unsuitable because the refractive error in each eye is not the same. Pinholes are ideal for such people because these glasses do not require a similar refractive error in each eye.
There is a pincushion effect when looking through the edges of prescription glasses. That is, straight lines appear curved. This disturbing effect does not occur with pinholes.
When you lay prescription glasses down improperly, they can easily get scratched at the center of the lens, the very area you have to look through. Scratching pinholes has no effect on their performance.
Pinholes do not have to be cleaned of fingerprints and other marks that affect vision.
Many parents will not allow their children to use bifocals to reduce the stress of close work because such glasses are for "old people." Pinholes are an easier thing to accept because they are the same for all ages.
Many people who have had corneal surgery find that their night vision has permanently deteriorated. Glare is a problem. They see halos and "starbursts" around lights. Even in normal home lighting they have problems so that they get in the habit of turning on as many lights as possible in order to get a small pupil and reduce the visual problems. Pinholes, either conventional or Snap-ons, can deliver the same small pupil without increasing the electric bill.
Children with special needs often use only their peripheral vision, and pinhole glasses help them concentrate on detail better. It has been found that the pinhole glasses help improve acuity and central macular vision. One nationwide organization that deals in child development uses pinhole glasses on a regular basis for this purpose.
Aniridia is the complete or partial absence of the iris; polycoria is having more than one pupil in a single iris; and albinism is the lack of normal pigmentation. All of these abnormalities may be aided with pinhole lenses.
In cases of retinal separation, unnecessary motion of the eyeballs should be avoided. This can be accomplished by blocking all but the central pinholes, forcing the user to turn the head rather than the eyes.

Using pinholes for cataracts. Many people with cataracts see better through pinholes. A cataract is one or more opacities in the lens that do not allow the light to pass through properly but instead cause it to scatter. By cutting off the peripheral rays, pinholes can reduce some of this scattering and improve the vision. Go to our Cataracts Page to learn how pinholes are actually used in this way and to see the new Snap-on Pinholes®.
Using pinholes as sunglasses. Who could imagine that pinhole glasses could be better sunglasses than conventional sunglasses? Well, it's true! This is such an intriguing and revolutionary concept that it deserves its own page. Don't fail to read Pinholes As Sunglasses.
Using pinholes as computer glasses. If you are looking for a way to reduce the visual stress of prolonged work at a computer, read Pinholes As Computer Glasses.
Limitations. One limitation of pinhole glasses is that blocking some of the light makes it more important than usual to have good lighting on the viewed object, even though the sharper image greatly compensates for the diminished light. When looking at television this is not a problem since the set makes its own light. When reading, a good lamp should be provided nearby. Another limitation is that peripheral vision is diminished, so they should not be used for driving or similar activities involving motion. As with any glasses, even sunglasses, they should not be used to stare at the sun, thinking that no harm can be done. For more detailed and somewhat technical information on the characteristics of pinholes, read Pinhole Details.
Pinholes cannot replace prescription glasses in every situation. People with over 6 diopters of myopia will probably not find pinholes useful, because pinholes cannot eliminate all of the blur. And just as it would be risky to wear ordinary glasses in situations where they could be broken and damage the eyes, there are situations where using pinholes instead of prescription glasses is not advisable. Use common sense and only wear the pinholes when the limited view does not pose a risk.
One group that should not use pinholes, or any glasses that reduce accommodation (focusing effort), is young people who are very farsighted. These people need to accommodate as much as possible in order to reduce their farsightedness to a lower level. This is nature's dynamic method of refining visual acuity in the growing youngster and it should not be defeated.
Can you imagine what the eye doctors and optical industry think about this inexpensive solution? The fact that you don't find pinholes in the optical stores and eye doctors don't recommend them should give you a hint. In fact, it is just this opposition that has resulted in government persecution of those who sold such glasses in the past. It is both enlightening and appalling to look at some cases which are representative of the Anti-pinhole Conspiracy.

To Order. Visit CaribbeanEyes and learn about the amazing world of pinhole glasses that look just like sunglasses! This is an important historic event, bringing to an end the decades-long suppression of this valuable device.

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