Focusing via Visual Accommodation

By changing its curvature, the eye’s lens causes light rays to converge so that they focus on the retina – a process known as accommodation.  You can observe this by dragging the candle along the optic axis. This focusing is only possible beyond a limit called the "punctum proximum" or "near point". Otherwise, the image is formed behind the retina and so is blurre.

The diagram is not drawn to scale!