The sensation of vision in the retina is carried to the brain by

If the far point of a short-sighted person is $400 \ cm$, then the power of the lens required to enable him to see very distant objects clearly is

$A$ man cannot see clearly the objects beyond a distance of $20 \, cm$ from his eyes. To see distant objects clearly,he must use which kind of lenses and of what focal length?

If the distance of the far point for a myopia patient is doubled,the focal length of the lens required to cure it will become

$A$ person wears glasses of power $-2.5 \, D$. What is the far point of the person without glasses in $cm$?

$A$ myopia patient uses: