The lens changes its refractive index to improve night vision, achieved by increasing aqueous humor production.

The lens changes its refractive index to detect motion, achieved by the movement of photoreceptors in the retina.

The lens changes its refractive index to focus light precisely on the retina, achieved by altering its shape through the action of the ciliary muscle.

The lens changes its refractive index to filter out harmful UV light, achieved by the pigmentation within the lens.