Eye Flashcards
Retina
Where the rod and cone cells are located. Contains light receptor cells
Rods
Detect light intensity
Cones
Detect colour
When there is a near object
- Ciliary muscle contracts
- suspensory ligaments loosen
- lens thickens
- so light is refracted STRONGLY
When there is a far object
- Ciliary muscles relax
- susepnsory ligaments tighten
- lens becomes thinner
- so light refracts less
Short sightedness
- Myopia
- rays of light focus in front of the retina
Long sightedness
Hyperopia
- where rays of light focus behind the retina
How can myopia be fixed
- using a concave lens to focus light on retina
How can hyperopia be fixed
- using a convex lense to focus light on retina
Treatments for myopia or hyperopia
- Hard and soft contact lenses (good for sport, comfortable)
- laser eye surgery (can change shape of cornea, which CHANGES HOW IT REFRACTS LIGHT ONTO THE RETINA)
- lens replacement surgery (replaces lens of eye with plastic artificial lens)
Laser eye surgery for myopia
- cornea is slimmed down, reducing refractive power
Laser eye surgery for hyperopia
Cornea shape is thickened so refractive power is increased
Risks and positives of hard contact lenses
- can be more uncomfortable
- causes damage if broken
- requires cleaning
- far more durable
- less environmentally damaging
Risks and positives of soft contact lenses
- more comfortable than hard contacts
- environmentally damaging
- higher risk of infection
Pupil reflex in dim light
- radial muscles of iris contract
- circular muscles of iris relax
- dilated pupil (more light enters eye)
Pupil reflex in bright light
- radial muscles relax
- circular muscles contract
- pupil is constricted (less light enters the eye)
Cornea
Transparent lens that refracts light as it enters eye
Iris
Controls how much light enters the pupil
Lens
Transparent disc that can change shape to focus light onto the retina
Retina
Contains light receptor cells
Optic nerve
Sensory neurone that Carries impulses between eye and brain
