Vision Flashcards
What are the retinal photoreceptor cells?
Rods and cones
What are cone cells?
They are cells used primarily for day or high intensity light vision. They provide sharp acuity and color perception.
The center of the fovea has the highest concentration of cone cells but no rod cells.
What are rod cells?
They are cells used for night or low intensity light vision.
The retina has the highest concentration of rod cells
What is rhodopsin?
An extremely light sensitive chemical, also referred to as visual purple. Typically found within rod cells but is highly suspectable to bleaching from bright light
How long does it take to dark adapt?
30-45 minutes
When fully adapted, rod cells become 10000 times more sensitive to light. Total light sensitively can increase to 100000 times with a completely dilated pupil
What is the day blind spot?
Where the optic nerve attaches to the retina, covers about 5.5-7.5*. No rods or cones are present at the attachment point.
Compensated with binocular vision
What are the types of vision?
Photopic
Mesopic
Scotopic
What is photopic vision?
Experienced during daylight or under high levels of artificial illumination.
Produces sharp images and color vision
Requires the use of central vision
Involves cones only
What is mesopic vision?
Experienced at dusk, dawn, and full moon.
Reduces color vision and visual acuity
Involves rods and cones
What is scotopic vision?
Occurs dimly lit nights
Decrease visual acuity: 20/200
Loss of color perception
Rods only, night blind spot
Requires peripheral vision
What is the night blind spot?
Occurs when the fovea becomes inactive in low light, involves area from 5-10* in the center field of vision
What is myopia?
Nearsightedness
A person who views an image at a distance, the focal point is in front of the retinal plane, causing blurred vision, making nearby objects more in focus
What is night myopia?
When people with myopia view something under blue-green light at night, they may cause blurred vision
What is hyperopia?
Farsightedness
The focal point is behind the retinal plane, causing blurred vision and further objects being more in focus
What is astigmatism?
The inability to focus different meridians simultaneously, resulting from an unequal curvature of the cornea or eye lens that causes a ray of light to spread over different areas of the retina
