The Eye and Vision
The eye focuses light on the retina.
About this topic
The eye focuses light onto the retina. Light enters through the cornea (which does most of the bending), passes the pupil, whose size the iris controls, and is focused by the lens. Ciliary muscles change the lens shape to focus on near or far objects. The retina has rods (dim light) and cones (colour), which send signals along the optic nerve to the brain.
The image is inverted and the brain corrects it. Short and long sight are corrected by lenses, and colour blindness results from missing cone types.
When you look at a near object, the ciliary muscles contract, the suspensory ligaments slacken and the lens becomes fatter, bending light more; for distant objects the reverse occurs. The retina has rods for dim light and cones for colour, with the highest density of cones at the fovea. Signals pass along the optic nerve to the brain, which flips the upside-down image.
Short-sightedness (myopia) happens when the image focuses in front of the retina and is corrected with concave lenses; long-sightedness is corrected with convex lenses. Colour blindness involves faulty cones. In dim light, the pupils widen to let in more light. A frequent confusion is between the cornea, which does most focusing, and the lens, which fine-tunes it. Also, the blind spot is where the optic nerve leaves, and has no receptors.
Key ideas
- Cornea and lens refract light
- Iris controls pupil size
- Optic nerve carries signals
Quick check
Use cases: where The Eye and Vision helps
- Homework: review the key idea behind The Eye and Vision before you start a problem set.
- Exam revision: use the quick check to test whether you can recall The Eye and Vision without notes.
- Visual learning: play with the interactive lab to see how The Eye and Vision changes when you adjust its inputs.
- Teaching a friend: explain The Eye and Vision in your own words, then compare your version with the key ideas.
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Frequently asked questions
What is The Eye and Vision?
The eye focuses light on the retina.
What will I learn in The Eye and Vision?
Cornea and lens refract light. Iris controls pupil size. Optic nerve carries signals.
Is The Eye and Vision part of Biology?
Yes. It is one of 150 Biology topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the The Eye and Vision lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study The Eye and Vision?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.