ELEMENTS ABOUT THE VISION

“Adjustment and focusing: All those whose hobby is photography are very familiar with the camera. The camera has certain devices that allow focusing images at different distances, from a close point to the infinity. The limit depends only on the lens features and on the adjustments that can be made to them. The human eye can also be adjusted to focus close or distant images. The closest point a young person with normal vision can focus with sharpness and clearness is about 17cm away from the viewer. And the remotest, the farthest point is located in the infinity. The infinity is considered the last point that can be naturally seen on the horizon line. There is a space between the closest and the remotest point; in the small lapse of time in which the eye captures the image, the luminous waves responsible for it travel all the way. Meanwhile, the eye accommodates itself to see either closer or farther. This space is called accommodation range. In a person with normal vision or emmetropic, the accommodation range goes from 17cm (close point) to the infinity (remote point).”

“Medicina e Saúde” Vol. 1 - Page 212 - Abril Cultural – 1968