How do glasses help to correct your vision?

Question from Darren Carlson

Our eyes provide vision by collecting light through our pupils (the black parts at the centre) and bending the light rays onto the retina at the back of our eye. Sometimes our eyes have problems with focussing these light rays, so require glasses.

The cornea and lens are responsible for bending light just right so that it focuses perfectly on the retina. But nearsighted people (who struggle to see things at a distance) focus the light in front of the retina, and longsighted people (who struggle to see things that are close) focus light behind the retina. Glasses with corrective lenses bend light before it reaches our eyes, which helps to ensure that the light ends up focused on our retinas.

Answered by James Horton for Brain Dump in How It Works issue 118 

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