Design Principles: What is a line? - Sight

Hyperopia, also known as farsightedness, longsightedness or hypermetropia, 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, and in extreme cases causing a sufferer to be unable to focus on objects at any distance. As an object moves toward the eye, the eye must increase itsoptical 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.


http://en.wikipedia.org/wiki/Hyperopia



Short-sightedness is a very common eye condition that causes distant objects to appear blurred, while close objects can be seen clearly. Myopia is the medical term for short-sightedness.
Cases of short-sightedness can range from mild, where treatment may not be required, to very severe, which can significantly affect vision.


http://www.nhsdirect.wales.nhs.uk/encyclopaedia/s/article/shortsightedness