Which part of the eye is the most powerful refractive surface?

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Multiple Choice

Which part of the eye is the most powerful refractive surface?

Explanation:
Light is bent most strongly at the front surface of the eye, where air meets the cornea. The large difference in refractive index between air and corneal tissue causes a sharp bend, giving the cornea about 40-something diopters of power. That single surface accounts for roughly two-thirds of the eye’s focusing ability. The lens does contribute additional focusing power and can adjust its shape to fine-tune focus for near or far objects, but its total power is smaller and it is flexible. The iris isn’t a refractive surface; it controls pupil size. The retina is the light-sensitive layer where the focused image lands, not a refractive element. So the cornea is the strongest refractive surface in the eye.

Light is bent most strongly at the front surface of the eye, where air meets the cornea. The large difference in refractive index between air and corneal tissue causes a sharp bend, giving the cornea about 40-something diopters of power. That single surface accounts for roughly two-thirds of the eye’s focusing ability. The lens does contribute additional focusing power and can adjust its shape to fine-tune focus for near or far objects, but its total power is smaller and it is flexible. The iris isn’t a refractive surface; it controls pupil size. The retina is the light-sensitive layer where the focused image lands, not a refractive element. So the cornea is the strongest refractive surface in the eye.

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