New Connecting Kids to Coverage Outreach Video. Learn about Las Vegas, Nevada's Foundation for Positively Kids outreach efforts using their network of community-based, school-based, and specialty health care clinics.
Young adults with 20/20 vision can often focus at 4 to 6 inches. At 6 inches, they can see detail at 600 pixels per inch or 300 line pairs per inch. As you age, your lenses become less resilient and the focus distance increases. At about 50 years, the average minimum focus distance is about a foot corresponding to 150 line pairs per inch or 300 pixels per inch. These numbers reflect good light and high contrast scenes. Generally, under more typical conditions, people don't see this well. --.
The eye is structurally designed to detect and process light. The cornea and the crystalline lens are both important for the eye to focus light. The eye focuses light in a similar way to when you use a magnifying glass to concentrate the Sunâs rays onto a piece of paper. The distance from the magnifying lens to the piece of paper is the focal length. For the eye, light from distant objects is focused onto the retina at the back of the eye. The eye is about the size of a table tennis ball, so the focal length needs to be about 2.5 cm.