Which structure fills the center of the eye and is composed mainly of water, accounting for about two-thirds of the eye's volume?

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Multiple Choice

Which structure fills the center of the eye and is composed mainly of water, accounting for about two-thirds of the eye's volume?

The center of the eye is filled by the vitreous humor, a clear gel-like substance that is largely water. Its watery composition helps it maintain the eyeball’s shape and provides a transparent medium through which light can pass to reach the retina. This fill occupies the large posterior chamber behind the lens and makes up about two-thirds of the eye’s volume, which is why it’s described as the main internal fill of the eye. In contrast, the aqueous humor sits in the front part of the eye—in the anterior and posterior chambers in front of the lens—and is not the substance that occupies the central cavity. The optic nerve is a bundle of nerve fibers that carries visual information to the brain, not a fluid fill. Accommodation refers to the eye’s adjustment of the lens shape to focus on near versus far objects, not a location within the eye.

The center of the eye is filled by the vitreous humor, a clear gel-like substance that is largely water. Its watery composition helps it maintain the eyeball’s shape and provides a transparent medium through which light can pass to reach the retina. This fill occupies the large posterior chamber behind the lens and makes up about two-thirds of the eye’s volume, which is why it’s described as the main internal fill of the eye.

In contrast, the aqueous humor sits in the front part of the eye—in the anterior and posterior chambers in front of the lens—and is not the substance that occupies the central cavity. The optic nerve is a bundle of nerve fibers that carries visual information to the brain, not a fluid fill. Accommodation refers to the eye’s adjustment of the lens shape to focus on near versus far objects, not a location within the eye.

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