Defective Vision Flashcards
Hypermetropia
Long sightedness (can’t see short distances).
Image forms before retina.
Have to have converging lens.
Myopia
Short sightedness (can’t see long distances).
Image forms before retina.
Have to have diverging lens.
Presbyopia
Long sightedness caused by age.
Elasticity of ciliary muscles reduces/ becomes less flexible with age, decreasing accommodation.
45-50 age.
Astigmatism
Imperfections in cornea or lens
Cause difficulties in resolving fine detail.
More common with age.
Can be SYMPTOMLESS.
(Individually tailored lens)
Cataracts
Colouring of lens
Can Lead to blindness
Often associated with age
Brought on : exposure UV light
Glaucoma
Pressure increase of liquid in eye. Can lead to blindness Cured: surgery / drugs Found: eye pressure test Acute pain in eye Blurred vision Sensitive high light levels Visual field deterioration.
Colour vision deficiency
Difficulty distinguishing colours Genetic inheritance CAUSED: Underlying health issues. - diabetes, glaucoma -side effect of meds Harmful UV Find out using ISHIHARA TEST(the numbers in weird colour pattern)
Flash blindness
Lightening flashes
- temporary blindness
Turn cockpits lights to MAX BRIGHTNESS
Wear sunglasses
Contact lenses
Could damage cornea - low levels of humidity
Easily dislodged
Bi-focal versions = prohibited
Pilots must carry normal glasses in case
Vision and speed
Speeds greater 450 knots at low light levels
(-visual input, brain reaction, perception, recognition, evaluation, decision M,action & responses) 5-7 seconds
Visual perception: cascade 1 second
Sunglasses
Impact resistant Thin metal frames Coated with polycarbonate - strength Good quality 10-15% luminance transmission Light sensitive lens (photochromic), generally FORBIDDEN. Polarised lens DISCOURAGED.
