Visual System Flashcards
What is the cornea
A transparent protective tissue that is located at the front of the eye
What is the iris
Round colored part of the eye that regulates the size of the pupils thus regulating the amount of light that enters
What does the pupil do
Allow light into the eye
What do cone cells do
Identifies color, 1:1 ratio for cone to neuron cells, produces lodosin
What are rod cells
Identifies shapes and silhouettes, have a poor visual acuity and poor color response though, 10:1 ratio to neuron cells
What is the fovea centralis
Contains only cone cells and provides day vision, allows for sharp 20/20 vision
What is considered a blind spot
Where the optic nerve sits there are no rods or cones there
What degrees is the day blind spot
5.5-7.5 degrees
What degrees is the night blind spot
5-10°
What component of the eye contains rods and cones
Retina
*What chemical lets you see black white and gray
Rhodopsin
*What is the function of the pupil when looking at an object
Pupil allows light to enter the eye and stimulate the retina
What is an astigmatism
Due to unequal curvature if the cornea you can not focus on vertical and horizontal features at the same time
Glare disability
Inability to detect objects against varying shards or backgrounds related to contrast
People with myopia
Have near sighted ness
Hyperopia
Farsightedness
What is presbyopia
Hardening of lens, loss of elasticity and cataracts
What are the types of corneal surgical procedures
LASIK PRK and LASEK
What surgical procedure is less likely to cause damage due to the thinness of the flap
LASEK
What is the condition result of blinded focal point behind renal plan or wall causing blurred vision (near objects are not seen well)
Hyperopia farsightedness
What is it called when lens becomes less elastic over time
Presbyopia
What are the three types of vision
Photopic, mesopic, scotopic
What is photopic vision
Daylight, central vision, color Spence and image is sharp, 20/20 vision
Mesopic vision
Transition day to night, dawn dusk moon light, use of parafoveal region (rods and cones), decreased visual acuity and color sense
What should you do during Mesopic vision
Use increased scanning, no hoist
What is scotopic vision
Night vision, peripheral vision (rods only), acutely degraded to silhouette recognition, loss of color perception, off center view technique
What type of vision is the most dangerous
Mesopic vision
Typed of monocular cues (GRAM)
Geometric, Retinal, Aerial, Motion
What monocular cue is most important for depth perception
Motion parallax
What is geometric perspective
Objects have different shapes when viewed at different angles Farther you are from an object the less detail there is compared to if you were closer
Geometric Perspective - LAV
- Linear perspective
- Apparent Foreshortening
- Vertical Position in the field
Retinal Image Size - KITO
- Known Size
- Increasing/decreasing size
- Terrestrial association
- Overlapping contours
How can you use terrestrial association
Compare one object to another object that you know the size off can help one estimate the size of the object you don’t know that size of
Aerial Perspective - FLP
- Fading
- Loss of detail
- Position of light source
What are the two aspects of motion parallax
Stationary objects and observing moving Rate depends on relative distance of the object from the observer
What are some limitations for night vision
Loss of depth perception, loss of visual acuity, night blind spots, dark adaption, color perception, night myopia, visual cues
What is dark adaptation time
30-45 min time it takes for eyes to adjust from rods to cones
Two most important monocular factors
Motion parallax Retinal image size
At night what is the best visual city you can get
20/200
With NGV at night what’s the best you can see
20/40
What vitamin helps with production of rhodopsin
A
What is night myopia
Blue wavelength pervades in visible position causes this
What are four examples of flight hazards
- Solar flare
- Birds
- Lasers
- Nerve agents
What are active ways to protect against lasers
Counter measures, evasive action scanning with one eye
What are some passive ways to protect against lasers
Take cover, squint, goggles
