AAMC FL Practice Exam

Which component of the eye is primarily responsible for focusing light onto the retina?

1. The cornea

2. The iris

3. The lens

4. The aqueous humor

The correct answer is: The lens

The lens is the component of the eye primarily responsible for focusing light onto the retina. Its primary function is to adjust its shape to help focus light rays that enter the eye at various distances. This ability to change shape is known as accommodation, which allows for clear vision both at close range and at a distance. The cornea also plays a significant role in light refraction, as it is the first part of the eye that light encounters and is responsible for most of the eye's total optical power. However, it is the lens that fine-tunes the focus after the light has passed through the cornea. The iris, while important for controlling the size of the pupil and regulating the amount of light that enters the eye, does not play a direct role in focusing light. The aqueous humor, a clear fluid in the front part of the eye, helps maintain intraocular pressure and provides nutrients but also does not contribute to focusing images on the retina. Therefore, recognizing the lens as the component that adjusts focus directly highlights its essential role in enabling clear vision.