Laser<unk>  also known as<unk>  can be employed as a method for conducting a very sensitive<unk>  test. When a surface is illuminated by a laser beam and is viewed by an observer, a<unk>  pattern is formed on the retina. If the observer has perfect vision, the image of the surface is also formed on the retina, and movement of the head will result in the<unk>  pattern and the surface moving together so that the<unk>  pattern remains stationary with respect to the background. If the observer is near-sighted, the image of the surface is formed in front of the retina. Since the<unk>  pattern is perceived by the brain to be on the retina, the effect is of parallax; the<unk>  pattern appears to be nearer to the<unk>  than the surface and hence moves in the same direction as the surface, but faster than the surface. If the observer is far-sighted, the<unk> s appear to move in the opposite direction as the surface, since in this case the surface image is focused behind the retina. The apparent speed of motion of the<unk> s increases with the magnitude of the defect of the<unk> . This technique is so sensitive that it can be used to determine changes in the ability of someone to focus through the day.
Eye testing using speckle
Retinal vessel analysis
Scanning laser ophthalmoscopy
Doppler optical coherence tomography
Retinal birefringence scanning
Humphrey visual field analyser
Fundus photography
Corneal topography