Online eye tests
The most commonly used test to detect color vision deficiencies was developed by the Japanese ophthalmologist Shinobu Ishihara. While working at the Military Medical School he was asked to devise a test to screen military recruits for abnormalities of color vision.
Eye dominance or ocular dominance, is the tendency to prefer visual input from one eye to the other. Both hemispheres control both eyes, but each one takes charge of a different half of the field of vision, and therefore a different half of both retinas.
Visual acuity is the clearness of vision, which is dependent on the sharpness of the retinal focus within the eye and the sensitivity of the interpretative faculty of the brain.
Illusions
Lilac chaser is a visual illusion, also known as the Pac-Man illusion. It consists of 12 lilac (or pink), blurred discs arranged in a circle (like the numbers on a clock), around a small black, central cross on a grey background.
A famous example of Professor Akiyoshi Kitaoka's rotating snake illusion. The shading in the image combined with the continuous random movement in our eyes, generate the movement illusions.
