12.1 Information Flashcards
Vision problems
Age can affect the ability to focus
Can be fixed by a lense
Far sightedness
Hyperopia
Can see close objects but not far objects
Light entering is focused on the retina and not directly on it
Eye cannot make the lense thick enough
Fix place converging convex lense
Near sightedness
Mytopia
Can see close objects clearly but not distant objects
Light entering is focused in front of the retina not directly on it
Eye can’t flatten lense to project
Place diverging I cave lense in front of eye
Astigmatism
Inability of the eye to form a clear image due to an irregularly shapes lense/cornea Cornea shapes like an oval or football Light focuses on more than one point 2 types horizontal and vertical Causes headaches and fatigue Fix glasses contacts laser surgery
Laser eye surgery
Involves correcting vision by reshaping the cornea using energy from a laser
Laser eye surgery benefits
Can correct near and far sightedness and astigmatism millions of success stories
Laser eye surgery risks
Poor night vision
Dry eyes
Long term effects are unknown
Total blindness
The person can not detect any light at all
Legally blind
People with very low vision or substantially reduced field of view
Can detect some light
Can form some image
Visual field is less than 20 instead of less than 180
Low vision
Most people can have most of their sight restored by glasses lenses or surgery
Lens capsule
An elastic bag that is like a bag that holds the lens in place
Cataract surgery
Front portion of the lens capsule is gently opened to remove the cataract
Cataractvis gently Brocken apart using ultrasonic vibrations
Cataract is vacuumed out
Lens capsule is left undistirved and tiny lens implant is inserted
Glaucoma
Caused by a buildup of vitreous humour fluid Fluid pressure collapses blood vessels No constant supply of oxygen Nutrients and neutrons dies Peripheral vision loss is tunnel vision
True colour blindness
Ability to only sheenshades of grey rare 1 in 40000
Colour vision defiexienxh
Ability to distinguish some colours but not others 1% females 8% males