# Convex and concave, hyperopia and myopia

How do you remember which is which?

To recap, convex lenses are used for hyperopia and concave lenses are used for myopia.

An easy way to remember this is:

Sight short (is great)

Focus short

Word short (myopia)

Have you noticed that the lenses used to correct this are also short in the middle? So –

Concave lenses are used to correct myopia.

So we get

Sight short (is great)

Focus short

Word short

Lens short (in the middle = concave)

And likewise

Sight long (is great)

Focus long

Word long (hyperopia)

have you noticed too that the lenses used to correct this are also long in the middle? So –

Convex lenses are used to correct hyperopia.

So we get:

Sight long (is great)

Focus long

Word long

Lens long (in the middle = convex)