For Your Eyes Only Trivia Quiz

Answer: Iris

The human iris is almost always shaded brown or black. The appearance of other colors such as green or blue is because of Tyndall scattering of light. The iris also controls the the diameter of the pupil which controls how much light makes it to the back of the eye.

Answer: Pupil

The pupil is the black dot surrounded by the iris. It absorbs light entering the eye and, with relatively little light exiting, it appears black. The actual pupil is somewhat smaller than it appears due to the magnifying effects of the cornea. In dim light, the pupil is somewhat larger and in bright light it is somewhat smaller.

Answer: Sclera

The sclera, or "white of the eye", contains collagen and elastic fiber. The white of the sclera contrasts with the color of the iris, which helps an observer see where someone else's eye is looking. If blunt force ruptures the sclera, it is very rare for full vision to return.

Answer: Cornea

The transparent cornea covers the iris and pupil. It is a reflex to close your eyelid when the cornea is touched because of the nerves in the cornea. Though the cornea is less than one millimeter thick, it has five layers: corneal epithelium, Bowman's layer, corneal stroma, Descemet's membrane, and corneal endothelium.

Answer: Optic disc

The optic disc is the head of the optic nerve, which connects the eye to the brain. The "blind spot" in your eye is caused by the lack of rods and cones there. A normally functioning optic disc is orange or pink. The optic disc is less than two millimeters in diameter.

Answer: Cone

Cone cells are photoreceptors that are found in the retina. They come in three types. Each type is sensitive to a different wavelength of light which allows them to perceive color. Cone cells are very small--measuring in micrometers.

Answer: Rod

Rod cells work better in dimmer light as opposed to cone cells which work better in brighter light. They tend to be found on the edges of the retina and are used in peripheral vision. Like cone cells, rod cells are also very small, measuring in micrometers.

Answer: Orbit

The orbit is a cavity in the cranium that holds the eye. In addition to the eyes, the orbits also contain several other structures including the extraocular muscles and the cranial nerves. The orbit has the volume of roughly one ounce.

Answer: Uvea

The term uvea comes from the Latin word "Uva" (grape). The uvea is in fact roughly grape sized and reddish-blue or black in color. The nutrition and gas exchange of the eye takes place in the uvea. It also serves to reduce the amount of reflected light inside the eye.

Answer: Vitreous body

Also called vitreous humor, the vitreous body is a gel-like substance in the space between the lens and retina. The vitreous body is four-fifths of the volume of the eyeball. It becomes more liquid like near its center. It has no blood vessels and is over 98% water.