Purchase of pinhole camera glasses

This is eyeglasses with small holes

(1) Focusing: the light reflected by an object must be focused on the retina before we can see the object clearly. The blurred vision caused by ametropia is that the parallel light reflected by distant objects cannot focus on the retina, and the focus is in front or behind the retina. Under normal circumstances, light enters the eye through the open pupil and reaches the retina through the cornea and most of the lens. Light passing through the periphery of the cornea and lens causes ametropia, resulting in blurred vision. If only the light beam through the center of the cornea and lens reaches the retina, any blurred vision caused by ametropia will be improved. The pinhole can exactly play this role, because the pinhole blocks the peripheral part of the light beam, and the central part of the light beam enters the eye through the pupil. Any corneal and lens induced ametropia is not so obvious. The pupil may be open, but the light beam received by the eyeball is only the central part. Although the light entering the eye is a little dim, it is all focused on the retina, so the image is clear.

(2) Light diffraction: can cover an eye, observe the phenomenon of wearing pinhole glasses. If we look at a small target in the distance through the center of the hole, and then turn our head to move the object to the next hole, we will notice three phenomena: first, the object near the edge of the hole is blurred; Second, if the head turns fast, the object seems to jump from the first hole to the second hole; Third, if the head turns slowly, we will see the double shadow, which is formed between the small holes. Half of the double shadow passes through one hole, and the other half passes through adjacent holes. In other words, the beating is going on. No objects can be seen through the eyeglasses without holes, but double shadows may be seen due to the diffraction of light. Diffraction is the change in direction of light as it passes through the edge of an object. We often see this phenomenon in our daily life, but we just don't pay attention to it. For example, when we see light passing through fog, small water particles make light diffract, resulting in aperture effect.

(3) Masking effect: if you are troubled by double shadow and jumping, you can choose pinhole glasses with larger distance between pinholes, because the opaque part between pinholes can mask this effect. However, if the opaque part is too wide, the honeycomb format is easy to notice.

(4) The function of eliminating the peripheral part of the beam: for some people, especially those with very small degree of ametropia, the above phenomenon can hardly be felt. However, refractive error is more serious, this phenomenon is more obvious. If the refractive error reaches a certain degree, even if the pinhole eliminates the peripheral part of the beam, the image may still be blurred. In fact, pinhole glasses can't overcome the phenomenon of double shadow and blurring in myopia, hyperopia and astigmatism with more than 6 diopters, so they can't be used. In addition, the scope of its use also depends on the distance of the object to be observed. For example, a person with deep myopia can only wear pinhole glasses when reading and working on the computer, and is not suitable for looking at distant targets. In addition, some nearsighted people may also have the opposite situation, wearing pinhole glasses to see far better, but not close.

(5) Improved vision: smaller aperture provides better vision, but reduces the amount of light entering the eye. Modern pinhole glasses look like sunglasses, with mirror coating on the front to reduce the reflection of light, so that the holes can be made larger. Larger holes, through each hole to see a larger range. Who is suitable to wear pinhole glasses? Anyone with poor eyesight can wear pinhole glasses. Eye fatigue, myopia, hyperopia, astigmatism, presbyopia, and even pinhole glasses for cataract patients can improve vision. But the effect is not good for those with ametropia more than 6 diopters. It is not effective for glaucoma and macular degeneration, which damage the optic nerve and retina. Pinhole glasses are not limited by age. Primary school students can wear them in order to prevent the aggravation of myopia caused by excessive reading. Presbyopia people over 40 can also wear them. Middle aged myopia patients can still wear them. The effect of pinhole glasses on mild ametropia is not obvious. Generally speaking, the effect of pinhole glasses is better for people with blurred vision