Far point

This article is about a measure of an individual's ability to see distant objects as clear and in focus. For other uses, see Farpoint.

In visual perception, the far point is the point at which an object must be placed along the optical axis of the eye for its image to be focused on the retina when the eye is not accommodating. It is sometimes described as the farthest point from the eye at which images are clear.

For an unaccommodated emmetropic eye, the far point is at infinity, but for the sake of practicality, infinity is considered to be 6 m because the accommodation change from 6 m to infinity is negligible.

For an unaccommodated myopic eye, the far point is closer than 6 m.

For an unaccommodated hypermetropic eye, incident light must be converging before entering the eye so as to focus on the retina. In this case the far point is behind the eye in virtual space, rather than in front of the eye.

This article is issued from Wikipedia - version of the Thursday, May 05, 2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.