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 typically rotates in its socket in order to focus images of objects at this location. The distance from the outer surface of the cornea (where the light undergoes most of its refraction) to the central portion of the fovea on the retina is approximately 2.4 cm. Light entering the cornea must produce an image with a distance of 2.4 cm from its outer edge. Unlike a camera, which has the ability to change the distance between the film (the detector) and the lens, the distance between the retina (the detector) and the cornea (the refractor) is fixed.