Which part of the eye gives it its color?
AnswerIris
The iris is the colored ring of muscle that controls the size of the pupil.
Science · Facts & stats
Eye facts & stats
7 fact-checked facts about the human eye and vision, each with the reason behind it. 5 more are in today's round and join this page after it closes.
The basics
Which nerve carries signals from the eye to the brain?
AnswerOptic nerve
The optic nerve carries visual signals from the retina to the brain.
Going deeper
Which cells in the retina are mainly responsible for color vision?
AnswerCones
Cone cells detect color and fine detail in bright light; rods work best in dim light.
Why does each eye have a blind spot?
AnswerThe optic nerve exits there, with no light-sensing cells
Where the optic nerve leaves the retina there are no rods or cones, so that spot cannot detect light.
What is the common medical term for nearsightedness?
AnswerMyopia
Myopia means distant objects look blurry while close objects are clear.
Expert level
How many types of cone cells do most humans have?
Answer3
Most people have three cone types, sensitive roughly to short, medium and long wavelengths of light.
The light-sensitive pigment in rod cells is built from a molecule derived from which vitamin?
AnswerVitamin A
Rhodopsin in rods uses retinal, a form of vitamin A, to detect light.
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