Do pin-hole glasses work?

  Have you heard about pin-hole glasses? It is a pair of glasses with no lens but full of tiny holes. Someone claims that wearing this glasses can help to cure short-sighted. Last month, when I shopped in a shopping mall with my wife, I discovered one. The price is only HKD 12 and was displayed like a toy. I bought it without hesitation.

  I cannot wait but unwrapped the package and had a trial. It was a sunny afternoon. I wore the pin-hole glasses and could see distinct objects clearly. "Let me have a try!" My wife didn't believe. After she wore the glasses, she was amazed. She has more than 400 degree short-sighted but she could see the text on a slogan far away.She then detached the pin-hole glasses and saw with naked eyes, the texts blurred. "What's magic behind that?" She exclaimed with joy. "It's pin hole effect. It is similar to squinting your eyes when you want to see far object clearly."I replied with proud and confidence.

  Let me explain the principle intellectually. As seen in the figure, if you have short-sighted, the image of far objects are always focused in front of the retina. Therefore, the images lied on retina are scattered and blurred. When you wear a pin hole glasses, the light beams passed through the eye lens are confined. The image will be likely condensed in a narrower area in retina although the focus is still taken place in front of the retina. Then you can have a clearer view. In order to achieve this, two things you should bear in mind. First, Pin-hole glasses can only contribute better vision on people who have sight problem. For people who have healthy vision, wearing it will have no effect and even worse. Secondly, as pin-hole confines most of the light, you should wear it in bright environment. Wearing in dimmed place will make the image in retina even darker and worse.

  The instruction printed on the package claims that wearing pin-hole glasses everyday for 3 minutes, you will have sight problem improved after one month. I have searched through the web about this. Some optician said this is just a cheat and useless at all. The reason is rational. Using a pin-hole glasses has no way to regulate the focus point which is the key factor of good vision. Whatever you wear it how many times, the focus point is still no change. But on the other hand, as human is complex, we cannot comprehend the psychological effect when someone can see far object clearly with naked eyes and pin-hole glasses. The brain may receive a fascinating message:"I can see clearly without Lens glasses!" Wearing pin-hole glasses may train the brain to enhance this faith and strive to see thing clearly with naked eyes. But it is pity that I am too lazy to prove this thought!