The doctor can see a certain reflection of the light in the pupil of the eye. He looks to see what the eye does with this light how the light moves. He repeats this through different lenses until he finds one where there doesn't seem to be any apparent movement at all. At this point, theoretically, the eye has been neutralized and the lens that does it is generally close to something that would be prescribed. Good sight is not synonymous with good vision, says Sirota.
Sight is the ability of the eye to see things.
Vision is the ability to make sense out of what one sees. Because of incidents like those descibed, Sirota began to question the degree to which this test is relied upon. But it was not until the following situation occurred that he found a way to build on the traditional test. One day, as the doctor was examining a very myopic patient, the phone rang. He had just neutralized what is called the against movement of light in the myopic eye and as he answered the phone, he told the patient to keep looking straight ahead.