Hyperopia, also known as farsightedness, longsightedness or hypermetropia, is a defect of vision

Visual system

The visual system is the part of the central nervous system which enables organisms to process visual detail, as well as enabling several non-image forming photoresponse functions. It interprets information from visible light to build a representation of the surrounding world...

 caused by an imperfection in the eye

Human eye

The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth...

 (often when the eyeball is too short or the lens

Lens (anatomy)

The crystalline lens is a transparent, biconvex structure in the eye that, along with the cornea, helps to refract light to be focused on the retina. The lens, by changing shape, functions to change the focal distance of the eye so that it can focus on objects at various distances, thus allowing a...

 cannot become round enough), causing difficulty focusing

Focusing

In psychotherapy-related disciples, the term focusing is used to refer to the simple matter of holding a kind of open, non-judging attention to something which is directly experienced but is not yet in words. Focusing can be used to become clear on what one feels or wants...

 on near objects, and in extreme cases causing a sufferer to be unable to focus on objects at any distance

Distance

Distance is a numerical description of how far apart objects are. In physics or everyday discussion, distance may refer to a physical length, or an estimation based on other criteria . In mathematics, a distance function or metric is a generalization of the concept of physical distance...

. As an object moves toward the eye, the eye must increase its optical power

Optical power

Optical power is the degree to which a lens, mirror, or other optical system converges or diverges light. It is equal to the reciprocal of the focal length of the device. The dioptre is the most common unit of measurement of optical power...

 to keep the image in focus on the retina.