Which structure in the eye contains no blood vessels and is critical for vision clarity?

The cornea is the transparent, dome-shaped surface that covers the front of the eye and plays a crucial role in focusing light onto the retina for clear vision. One of its unique characteristics is that it contains no blood vessels; instead, it receives nutrients from the tears and the aqueous humor, the fluid in the front chamber of the eye. This avascular nature is significant because it minimizes obstruction that could scatter light, thus maintaining clarity and preventing interference with vision.

In contrast to the cornea, the lens is indeed avascular as well, but it primarily adjusts focus rather than serving as a protective, light-refracting surface. The retina contains blood vessels that supply it with necessary nutrients and oxygen, while the iris, although it regulates the amount of light entering the eye, does not have the same role in directly contributing to vision clarity. Therefore, the cornea is the correct choice as it is essential for maintaining a clear view while lacking blood vessels that could distort vision.