Hyperopia, also known as farsightedness, is a defect of vision caused by an imperfection in the eye often when the eyeball is too short or the lens cannot become round enough, causing difficulty focusing on near objects. In extreme cases, it may cause a sufferer to be unable to focus on objects at any distance.
As an object moves toward the eye, the eye must increase its optical power to keep the image in focus on the retina. If the power of the cornea and lens is insufficient, as in hyperopia, the image will appear blurred.
Hyperopia is often confused with presbyopia, another condition that frequently causes blurry near vision. Presbyopes who report good far vision typically experience blurry near vision because of a reduced accommodative amplitude brought about by natural aging changes with the crystalline lens.
The causes of hyperopia are typically genetic and involve an eye that is too short or a cornea that is too flat, which causes images to focus at a point behind the retina. Hyperopia is most commonly corrected through the use of corrective lenses, such as glasses or contact lenses. The corrective lenses have a positive optical power which compensates for the excessive negative diopters of the hyperopic eye.