Answer to Question #23100 in Optics for Annelies

Question

when you use the formula Nh=25cm/f, and your eye loses some ability of accomodation, will the Nh become bigger or smaller?

Answer 1

As an eye loses stability ofaccommodation, it fails to focus on objects that are located at distances other than Nh. The optimal seeing distance Nh, which is 25 cm normally, can become either bigger (for far-sighted people) or smaller (for near-sighted people). It is usual that the loss of accommodation (e.g. with age) tends to be far-sighted and thus Nh grows over time. (i.e. accommodation is needed to perceive closer objects).