**Core Concept**
The refractive index of the cornea is a critical parameter in ophthalmology, influencing the eye's ability to focus light. The cornea's refractive index is higher than that of the surrounding aqueous humor, allowing it to contribute significantly to the eye's total refractive power.

**Why the Correct Answer is Right**
The correct answer, 1.37, is a well-established value for the refractive index of the cornea. This value is a result of the cornea's unique composition, primarily consisting of water, collagen, and other proteins. The refractive index of the cornea is influenced by the arrangement of its collagen fibers, which are densely packed in a specific pattern. This arrangement allows the cornea to refract light efficiently, contributing about two-thirds of the eye's total refractive power. The refractive indices of the cornea and the lens work together to focus light on the retina, enabling vision.

**Why Each Wrong Option is Incorrect**
**Option B:** 1.33 is the refractive index of water, which is incorrect for the cornea, as it is composed of a mixture of water and other substances.
**Option C:** 1.42 is too high and not representative of the cornea's refractive index, which is actually lower than that of the lens.
**Option D:** 1.45 is also too high and not accurate for the cornea's refractive index.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the cornea's refractive index is not uniform throughout its thickness. The anterior stroma has a higher refractive index than the posterior stroma, which contributes to the eye's total refractive power.

**✓ Correct Answer: A. 1.37**