Do Pinhole Glasses Work?

Pinhole glasses. Volanthevist

Question: Do Pinhole Glasses Work?

You may have heard about the benefits of pinhole glasses. Do they really work? Could pinhole glasses be useful for you?

Answer:

Many companies, including several on the web, advertise pinhole glasses. These companies often make extravagant claims about their benefits. You may have read that pinhole glasses clear vision by reducing refractive errors and permanently improving vision.

However, no evidence exists to fully support these claims.

What Are Pinhole Glasses?

Pinhole glasses, also called stenopeic glasses, are eyeglasses with lenses that consist of many tiny holes filling an opaque sheet of plastic. These "pinholes" block indirect rays from entering the eye, thus preventing them from distorting your vision. While this does not actually improve the focusing ability of the eye, it does reduce the size of the blur circle on the back of the retina, so reasonably clear vision may be achieved.

How Do They Work?

We have all experienced this phenomenon by squinting our eyes to improve vision.  Squinting achieves the same thing. It reduces the size of the de-focus light rays that land on the retina. You can do the same thing by making a small circle with your thumb and your pointing finger and looking through it. Of course, those of us that do not have any significant vision problems will not notice much difference.

However, people that wear corrective lenses will notice an improvement, sometimes a significant improvement.

If you try on a pair of pinhole glasses, you may actually notice an improvement in your vision. However, while wearing the pinhole glasses, vision is quite obstructed by the black spaces around the pinholes.

There seems to be a trade off in the clarity of vision compared to the amount light being let through. If you make the holes infinitely small, vision will be better, but the amount of light is so restricted that the quality of vision is horrible.

Benefits of Pinhole Glasses

Pinhole glasses are mainly used by eye care specialists as a diagnostic tool. Many eye doctors use an occluder, an instrument used to cover one of your eyes while reading the eye chart. On one end, the occluder is solid. On the other end, the occluder has many tiny pinholes. Sometimes doctors use this to quickly see the potential of your vision. For example, if someone comes in for an office visit for an eye infection and they can only read the 20/70 size of letters on the eye chart, the doctor will wonder, “Is this person’s vision 20/70 because of the eye infection, or could part of that decreased vision be due to a being nearsighted?" To quickly find out if that patient’s vision could potentially see better than 20/70, the doctor may perform a “pinhole” visual acuity test.

If the patient looks through the pinholes and reads 20/25, then it could be assumed that most of the decreased vision is not due to the infection, but rather some type of uncorrected vision problem. It may be safe to assume that the infection may be reducing the vision only slightly. The doctor may not have time to find out what type  of the prescription the patient might need, because the person may have come in only to have the infection treated. Therefore, the pinhole test is a very quick way to find out more information about a person’s eye condition. Pinhole glasses are used in other ways to evaluate corneal distortion and cataracts.

Who uses pinhole glasses?

For most of us, pinhole glasses are not socially acceptable to wear in public and not functional enough to wear for day to day tasks. However, some people have stated that they prefer them to wearing a bifocal or trifocal. Pinhole glasses are inexpensive and provide fairly clear vision at all distances, whereas a bifocal may have limitations at certain distances.

People who have a significantly high prescription and break or lose their glasses may want to keep a pair of pinhole glasses around. While they do not perform perfectly, they will be good enough for emergency purposes. Patients with aniridia may also benefit from pinhole glasses. Aniridia describes a complete or partial absence of the iris. The iris acts to control the amount of light allowed to enter the eye. When the iris is absent, the patient may suffer debilitating glare and visual distortion where regular glasses or sunglasses do not help. The pinhole glasses will limit the amount of light coming in and produce much clearer vision.

Most people would be reluctant to wear pinhole glasses, as they are not very fashionable. Also, it should be noted that pinhole glasses not only reduce brightness but also decrease peripheral vision, and therefore are unsafe to wear while driving or operating machinery. In almost all cases, other forms of correction will obtain clearer vision.  

Source:

Optometrists Association Australia. Pinhole Spectacles. Copyright 2008

Optometrists Association Australia. Pinhole Spectacles. Copyright 2008.

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