A needle and thread blurred close to the camera, the lamp-lit room behind them sharp.

How eyes focus

Hyperopia

Optical glossaryHow eyes focus

Farsightedness: light would focus behind the retina, making near work effortful. Corrected with plus lenses.

Nearsightedness brings distant light to a focus in front of the retina, farsightedness behind it. A minus or a plus lens moves the focus back onto the retina.

Illustrative · the shape of the principle, not measured data

In more depth

A farsighted eye is optically too weak for its length, so light would come to a focus behind the retina. A young eye can make up the difference by focusing harder, which is why farsightedness often goes unnoticed for years and shows itself as tiredness or headaches after close work rather than blur.

A plus lens supplies the missing power. Plus lenses are thickest in the center and slightly magnify, and because a farsighted eye has already been spending its focusing reserve, the need for reading help tends to arrive earlier than it does for others.

Related terms

Sphere (SPH)The main power of your prescription, in diopters. Minus corrects nearsightedness, plus corrects farsightedness; further from zero means stronger.MyopiaNearsightedness: distance is blurred because light focuses in front of the retina. Corrected with minus lenses.PresbyopiaThe age-related stiffening of the eye's internal lens that makes close focus difficult, typically from the early forties. Not a disease — the reason reading additions and progressives exist.Addition (ADD)The extra reading power added to the lower part of a progressive or bifocal. Typically starts near +1.00 in the early forties and usually settles near +2.50 (up to +3.00 for close working distances).

Go deeper on this site