Near point | EPFL Graph Search

Are you an EPFL student looking for a semester project?

Work with us on data science and visualisation projects, and deploy your project as an app on top of GraphSearch.

In visual perception, the near point is the closest point at which an object can be placed and still form a focused image on the retina, within the eye's accommodation range. The other limit to the eye's accommodation range is the far point. A normal eye is considered to have a near point at about for a thirty year old. The near point is highly age dependent (see accommodation). A person with hyperopia or presbyopia would have a near point that is farther than normal. Sometimes, near point is given in diopters (see ), which refers to the inverse of the distance. For example a normal eye would have a near point of . A person with hyperopia has a near point that is further away than the typical near point for someone their age, and hence the person is unable to bring an object at the typical near point distance into sharp focus. A corrective lens can be used to correct hyperopia by imaging an object at the typical near point distance D onto a at the patient's actual near point, at distance NP. From the thin lens formula, the required lens will have optical power P given by The calculation can be further improved by taking into account the distance between the spectacle lens and the human eye, which is usually about 1.5 cm: For example, if a person has NP = 1 m and the typical near point distance at their age is D = 25 cm, then the optical power needed is P = +3.24 diopters where one diopter is the reciprocal of one meter.

About this result

This page is automatically generated and may contain information that is not correct, complete, up-to-date, or relevant to your search query. The same applies to every other page on this website. Please make sure to verify the information with EPFL's official sources.

Related concepts (3)

Near point

Dioptre

A dioptre (British spelling) or diopter (American spelling), symbol dpt, is a unit of measurement with dimension of reciprocal length, equivalent to one reciprocal metre, 1 dpt = 1 m−1. It is normally used to express the optical power of a lens or curved mirror, which is a physical quantity equal to the reciprocal of the focal length, expressed in metres. For example, a 3-dioptre lens brings parallel rays of light to focus at metre. A flat window has an optical power of zero dioptres, as it does not cause light to converge or diverge.

Optics

Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultraviolet, and infrared light. Because light is an electromagnetic wave, other forms of electromagnetic radiation such as X-rays, microwaves, and radio waves exhibit similar properties.