The lens is a transparent biconvex structure in the eye that, along with the cornea, helps to refract light to be focused on the retina.
<img src="https://upload.wikimedia.org/wikipedia/commons/thumb/8/81/Focus_in_an_eye.svg/1920px-Focus_in_an_eye.svg.png" width="500">
<img src="https://upload.wikimedia.org/wikipedia/commons/thumb/1/1e/Schematic_diagram_of_the_human_eye_en.svg/1024px-Schematic_diagram_of_the_human_eye_en.svg.png" width="500">
From [Wikipedia](https://en.wikipedia.org/wiki/Lens_(anatomy)) under [CC BY-SA 2.5](https://creativecommons.org/licenses/by-sa/2.5/) and [CC BY-SA 3.0](https://creativecommons.org/licenses/by-sa/3.0/) licenses.