Accommodation, rods and cones
| English | Chinese | Pinyin |
|---|---|---|
| accommodation | 视觉调节 | shì jué tiáo jié |
| ciliary muscles | 睫状肌 | jié zhuàng jī |
| rods | 视杆细胞 | shì gān xì bāo |
| cones | 视锥细胞 | shì zhuī xì bāo |
Focusing near and far
- Your eye can switch focus from a distant hill to a book in your hands almost instantly.
- This focusing is accommodation 视觉调节, and seeing in colour and dim light depends on two cell types.
To focus on a NEAR object, the lens becomes:
A fatter lens bends light more for near objects.
The eye changing focus between near and far objects is called ______.
The lens changes shape to focus at different distances.
Accommodation
- The lens changes shape to focus on near or far objects.
- For near objects: the lens becomes fatter (more curved).
- For far objects: the lens becomes thinner (flatter).
The eye focuses light onto the retina; the lens changes shape to focus on near or far objects
Accommodation — focusing the eye
The eye changes the shape of its lens to focus on near or far objects.
The lens shape is changed by the:
Ciliary muscles (and suspensory ligaments) change lens shape.
Controlled by the ciliary muscles 睫状肌
- The ciliary muscles and suspensory ligaments change the lens shape.
- Near object: ciliary muscles contract, lens fattens. Far object: they relax, lens flattens.
Rods are light-sensitive cells that:
Rods are sensitive in dim light; cones detect colour.
Cones detect colour and work best in bright light.
Cones need bright light; rods handle dim light.
Rods 视杆细胞 and cones 视锥细胞
- The retina has two light-sensitive cells: rods and cones.
- Rods: very sensitive, work in dim light, but give no colour. Cones: need bright light, detect colour.
In the dark you see in black and white. Only rods work in dim light, and they can't detect colour. That's why colours fade at night even though shapes are still visible.
You've got it
- accommodation: the lens fattens for near objects, flattens for far ones
- the ciliary muscles change the lens shape (contract = fatter lens)
- rods = dim light, no colour; cones = bright light, colour