Pinhole glasses
Pinhole Glasses
Pinhole glasses, also known as stenopeic glasses, are eyeglasses with a series of pinhole-sized perforations filling an opaque sheet of plastic in place of each lens.
Pronunciation
Pinhole glasses: /ˈpɪnˌhoʊl ˈɡlɑːsɪz/
Etymology
The term "pinhole" comes from the English words "pin" and "hole", referring to the small holes in the glasses. The term "stenopeic" comes from the Greek words "steno" meaning narrow, and "ope" meaning hole.
Function
Pinhole glasses are said to improve visual acuity for people with refractive errors such as myopia, hyperopia, presbyopia, and astigmatism. These glasses work on the principle of reducing the amount of light that enters the eye, which reduces the size of the circle of confusion on the retina and increases depth of field.
Related Terms
- Refractive error: A problem with the eye's ability to bend light correctly.
- Myopia: Also known as nearsightedness, a condition where close objects appear clearly, but far ones don't.
- Hyperopia: Also known as farsightedness, a condition where distant objects may be seen more clearly than objects that are near.
- Presbyopia: A condition that results in difficulty in reading or seeing at close distances.
- Astigmatism: A common vision condition that causes blurred vision due to the irregular shape of the cornea.
- Visual acuity: Sharpness of vision, measured by the ability to discern letters or numbers at a given distance according to a fixed standard.
- Circle of confusion: In optics, a circle of confusion is an optical spot caused by a cone of light rays from a lens not coming to a perfect focus when imaging a point source.
- Depth of field: The distance between the nearest and the furthest objects that are in acceptably sharp focus in an image.
External links
- Medical encyclopedia article on Pinhole glasses
- Wikipedia's article - Pinhole glasses
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