The lens and the cornea together are responsible for bending the light rays from an image so that they focus on the retina (back of the eye). The lens changes shape to keep objects at different distances in focus. For example, when focusing on objects at a close distance, the lens contracts. When focusing on objects far away, the lens elongates. As we age, the lens loses its flexibility, and therefore its ability to contract. This makes it harder to keep objects close to us in focus, for which the medical term is presbyopia. This is a normal part of aging. Individuals start to notice difficulty reading the newspaper, restaurant menus, or their books. To compensate, one can hold objects further away, however eventually will need near-vision correction, such as reading glasses.
Here is a video that presents an overview of presbyopia. You may change the audio and subtitles to the language of your choice by hovering over the bottom right of the video and clicking on the “CC” icon.
The video below gives an overview of treatment options for presbyopia.