The Eye PMT Flashcards
Describe how dim light affects the size of the pupil
- Light receptors detect dim light
- Circular muscles relax
- Radial muscles contract
- Pupil dilate
- More light enters the pupil
Describe how bright light affects the size of the pupil
- Light receptors, detective bright light
- Circular muscles contract
- Radial muscles relax
- Pupil contracts
- Less light enters the pupil
Why is the Iris reflex important?
It prevents bright light from damaging the retina
What is accommodation?
- Process by which the elastic lens changes its shape to focus on near or distant objects
- Light is focused onto the retina
Describe how the eye focuses on near objects
- Ciliary muscles contract
- Suspensory ligaments slacken
- Lens becomes more convex
- Light is refracted more
- Light rays focused onto the retina
Describe how the eye focuses on distant objects
- Ciliary muscles relax
- Suspensory ligament tighten
- Lens becomes less convex
- Light is refracted less
- Light rays focused onto the retina
What is long sightedness?
an focus on distant objects clearly but not near objects
What are the causes of long sightedness?
- Eyeball is too short
- Lens is less elastic
- Therefore light ray are not focused onto the retina, instead converging behind the retina
How is long sightedness treated?
- Using a convex lens in glasses or contact lenses
- Replacement lenses
- Laser eye surgery
What is short sightedness?
Can focus on near objects clearly but not distant objects
What are the causes of short sightedness?
- Eyeball is too long
- Lens is too thick and too rounded
- Therefore light rays are not focused onto the retina, instead converging in front of the retina
How is short sightedness treated?
- Using a concave lens in glasses or contact lenses
- Replacement lenses
- Laser eye surgery
What are cataracts?
- A cloudy patch forms on the lens of the eye which negatively affects vision due to a protein buildup
- Vision becomes blurry, difficult to see the intensity of colours
How are cataracts treated?
The clouded lens is exchanged for a synthetic lens during surgery
What is colour blindness?
A deficiency of the eye that makes it difficult to distinguish between colours
What is the cause of colour blindness?
Damage to cone cells in the retina
