What is the strength of the cornea as a refracting surface?

The strength of the cornea as a refracting surface is indeed approximately +43 diopters. This value indicates the cornea's ability to bend light as it enters the eye, playing a crucial role in focusing images on the retina. The cornea contributes the majority of the eye's total refractive power, primarily due to its curved shape and the significant difference in refractive indices between air and the corneal tissue.

When light travels from air into the cornea, it slows down and bends, allowing for proper focusing. The corneal surface's curvature and the refractive index of the tissues surrounding it set this power around +43 diopters. This value is essential for understanding how focusing mechanisms work in the eye, influencing conditions such as myopia (nearsightedness) and hyperopia (farsightedness).

While the other options present values that are higher or lower than the accepted refractive power of the cornea, the specific nature of the cornea's anatomical and optical properties validates the selection of +43 diopters as the most accurate representation of its refracting strength.