What is the refractive power of the cornea?

What is the refractive power of the cornea?

• A. 40 diopters
• B. 45 diopters
• C. 43 diopters
• D. 50 diopters

Answer: (C)

The cornea provides the majority of the eye’s refractive power, and its typical value is about 43 diopters. This high convergence mainly comes from the large index jump when light moves from air into the cornea combined with the cornea’s steep curvature. The anterior surface contributes the bulk of this power (roughly +48 D), while the posterior surface (from cornea to the aqueous) partially offsets it, making the net power closer to the mid-40s. When you include the cornea’s finite thickness, the total becomes about 43 D on average. That’s why 43 diopters is the best answer—the common, well-established corneal refractive power used in exams and keratometry readings. Other options are outside the typical range: about 40 D is a bit low, 45 D is a bit high, and 50 D would be much higher than average. The cornea’s power is generally cited near 42–44 D, with 43 D being a handy representative value.

The cornea provides the majority of the eye’s refractive power, and its typical value is about 43 diopters. This high convergence mainly comes from the large index jump when light moves from air into the cornea combined with the cornea’s steep curvature. The anterior surface contributes the bulk of this power (roughly +48 D), while the posterior surface (from cornea to the aqueous) partially offsets it, making the net power closer to the mid-40s. When you include the cornea’s finite thickness, the total becomes about 43 D on average. That’s why 43 diopters is the best answer—the common, well-established corneal refractive power used in exams and keratometry readings.

Other options are outside the typical range: about 40 D is a bit low, 45 D is a bit high, and 50 D would be much higher than average. The cornea’s power is generally cited near 42–44 D, with 43 D being a handy representative value.