Pinholes!

Have you ever seen an infomercial in the wee hours of the morning, with each testimonial professing that the only thing stopping you from perfect vision is a lack of pinhole glasses?

Well, to some extent, pinholes are great for vision! The main reason that people need glasses is that light rays coming into the eye are not focused on one point in the retina. Well, the limit of narrowing the amount of light coming into the eye would be just one light ray, and if there is just one light ray, it will hit the center of the retina and there will be no need to focus multiple rays onto a single point. So, narrowing the “window” allowing light into the retina will sharpen up the image as an approximation to reducing the light allowed in to a single light ray. This is why we often check vision in the office using a “pinholer.”