Laser Eye Exam

Laser eye exam:  People generally do not have perfect vision and many wear eyeglasses or contact lenses. People who are near sighted see near objects well and distant objects are out of focus.  In the eye the image of distant objects is not on the retina, where it should be, but in front of the retina.  Conversely, persons who are far sighted see distant objects quite well, but nearby objects are out of focus. In the eye, the image of nearby objects is not on the retina but behind it.  A laser beam directed onto a surface generally produces a speckle pattern (grainy pattern), or interference pattern produced by scattering from different parts of the surface.  The speckles are larger for those with poor vision.  The mind assumes the speckle pattern is formed on the retina.  So movement of the head produces a movement of the speckle pattern. For near sighted people the speckle pattern moves opposite the direction of the head.  For far sighted people, the speckle pattern moves in the same direction as the head.