Chapter 9 - The Eye Flashcards
- Define ‘Accommodation’ in respect of vision.
- The changing shape of the lens as it focuses on near and distant objects, facilitated by the ciliary muscles.
What is the ‘Iris reflex’?
The iris changing size according to available light.
What is the iris/pupil configuration in:
A. Low light
B. Bright light
A. Large pupil, narrow iris (iris contracts)
B. Small pupil, wide iris (iris relaxes)
What is ‘focal length’?
The distance between the lens and the focal point.
- What is a convex (converging) lens used to correct?
2. What is a concave (diverging) lens used to correct?
- Long-sightedness
2. Short-sightedness.
- Describe the function of the cornea.
2. Describe the adaptations of the cornea.
- Protects eye surfaces, and focuses light rays.
2. Is clear, colourless and curved.
- Describe the function of the lens.
2. Describe the adaptations of the lens.
- Focuses light onto the retina.
2. Is clear, colourless, curved, and can change shape.
- Describe the function of the retina.
2. Describe the adaptations of the retina.
- Detects light waves and produces impulses.
2. Contains rod cells, cone cells, and sensory neurones.
- Describe the function of the iris.
2. Describe the adaptations of the iris.
- Controls pupil size, and regulates amount of light entering the eye.
- Contains muscles.
- What is long-sightedness?
2. What is short-sightedness?
- When close objects are blurry.
2. When far objects are blurry.
- What is long-sightedness caused by?
2. What is short-sightedness caused by?
- An eyeball that is too short, or the cornea isn’t curved enough.
- An eyeball that is too long, or the cornea is too curved.
- What cells in the retina cause colour blindness?
- Cones.
- Name the eye problem that can be fixed by replacing the lens.
- Cataracts.
What muscles operate the lens?
Ciliary muscles.
What cells detect low levels of light?
Rods
What cells detect colour?
Cones.
What causes the pupil to dilate and constrict?
Iris muscles.
Why is it necessary for the iris muscles to cause the pupil to construct and dilate?
To control how much light enters the eye in order to protect the retina.
In which order does light reach the parts of the eye?
- Cornea
- Pupil
- Lens
- Retina
Can short-sightedness be corrected with surgery?
Yes
Can long-sightedness be corrected with surgery?
Yes
Can colour blindness be corrected with surgery?
No
Can cataracts be corrected with surgery?
Yes
How are cataracts corrected?
By removing the lens and replacing it with a plastic one.
How is long/short-sightedness corrected?
By using lasers to reshape the cornea.
What is the function of the optic nerve?
To transmit impulses to the brain.
Where is the blind spot in the eye?
Where the optic nerve attaches to the eye.
What is contained within the fovea?
Lots of cone receptors that give the best visual acuity.
What is the medical name for long-sightedness?
Metropia
What is the medical name for short-sightedness?
Myopia
What causes colour blindness?
It is a genetic defect primarily affecting boys that is passed to them by their mother.
What is the medical name for colour blindness?
Deuteranomoly
What are cataracts?
Damaged lens proteins that cause the lens to become cloudy.
What causes cataracts?
Dietary deficiency and long-term exposure to bright sunlight.
Where do rods and cones send signals?
Down the optic nerve to the visual area at the back of the cerebrum.
