Which structure is primarily refracting light to help focus images on the retina?

• A. Lens
• B. Iris
• C. Conjunctiva
• D. Cornea

Answer: (A)

The lens is responsible for adjusting the focus of light onto the retina through accommodation. Light first encounters the cornea, which provides most of the eye’s refractive power, but the lens fine-tunes that focus and changes shape to keep images sharp at different distances. When you look at something far away, the lens relaxes and becomes thinner; for near objects, it thickens and increases its refractive power to converge the light onto the retina.

The other structures don’t perform this focusing adjustment. The iris controls how much light enters the eye, not how it’s bent to form an image. The conjunctiva is a protective membrane and doesn’t refract light. The cornea contributes most of the refraction but doesn’t adjust for distance like the lens does.