You can check the vision with laser pointer

If you have ever interacted with a laser pointer, you may have noticed that the light coming from it are not uniform, and grainy, with light and dark spots. This phenomenon is called laser speckle.

At first glance it may seem that the laser speckle - just a picture projected on the wall, but this is not true. The fact that all aspects distinguish speckle image can even people with impaired vision without glasses. However, the light waves reflected from the wall at slightly different angles, and you can see some parts of the image brighter, and some - darker. Again, it really is not bright and dark spots as such - and the wave interference between the wall and the eyes.

This means that your eyes are playing in the interaction between you and the image of a key role. If you move your head at speckle, you can see whether you have nearsightedness or farsightedness. Nearsighted people will notice that speckle will shift to the opposite side of the movement of the head, while the far-sighted - to move in the same direction.

Speckle image - a beautiful eyesight test. People with perfect vision when moving his head to notice that the stains on the wall start to tremble slightly, but the image itself remains in place. With the test, you can even keep track of small changes during the day.

via factroom.ru