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Farsighted

Farsighted = hyperopia

Imagine a table tennis ball with the front part removed and replaced by a bit of glass from a window. The entering light follows its path unbroken. There is no imaging and at the back of the ball one can see a light blurry spot. 

If we remove the window glass by some glass that has a slight bend, a burning point will form. Initially this will still be far behind the eye, but as the glass thickens in the middle the burning point will come closer to the front, thereby nearing the retina. Still there is no clear image. This condition is called being farsighted or hyperopia. 

The brain realises that the image isn't sharp. The eye's own lens is stimulated to help. The activity, also called accommodation, is harmless. One can however experience a headache or tiredness at the end of a day.

Wearing a plus glass generally takes care of these symptoms. It also makes the vision more focused and sharper. Plus (+) dioptres require convex lenses (middle is thicker than the edge), since the plus allows extra bending in the light beams, which is needed to guide the directions of the lightbeams in a farsighted eye.

The eye's lens is able to project an image onto the retina through means of accommodation for many years. This is why people with slight farsighted sight never require lenses or glasses. They do however, around the age of 35 instead of 45, start having vision problems whilst reading and require reading glasses.