2. How Pinhole Glasses Work

The theory of how pinhole glasses work

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a. The unaided weak eye without Pinhole Glasses

Diagram 1

In a weak eye, light rays entering the eye's lens are not all focused onto the same place on the retina. For example rays a b f g, require more focusing by the lens to hit the same plane as rays c d e, which are nearer to the centre. Rays c d e are usually always in focus, regardless of the condition of the eye, and form a clear image on the retina. This clear image is flooded by the blurred image known as the "blur circle" formed by rays a b f g.

b. The unaided weak eye with Pinhole Glasses

Diagram 2

When the pinhole lens is used, only rays c d e are allowed to form an image on the retina and no blur circle is present to block the clear image. Consequently, by using a lens with multiple pinholes, many focused images form on the retina and a clear, natural image is seen. Also, no effort is required from the eye muscles, as the only rays entering the eye are already in focus. Hence there is a dramatic consequential, relaxing effect.

3. Evidence