Which surface of the iris is responsible for determining the color of the eyes?

The anterior surface of the iris is responsible for determining the color of the eyes. This surface contains varying amounts of pigment, specifically melanin, which influences eye color. A higher concentration of melanin results in darker eye colors, such as brown, while lower concentrations contribute to lighter colors, such as blue or green. The structural characteristics of the anterior surface, including its texture and the light that reflects off of it, also play a role in how the color is perceived.

In contrast, the posterior surface of the iris is not involved in determining eye color; it is primarily responsible for providing a darker backdrop that enhances the appearance of the anterior surface. The ciliary body supports the iris and plays roles in focusing but does not influence eye color directly. The pupil, being the opening that allows light to enter the eye, does not have any significance in determining the color of the iris itself. Thus, the anterior surface is crucial for providing the characteristic colors we observe in human eyes.