TYPES OF VISION

Question 1

What are the 5 major components of the eye?

Answer 1

1) Cornea
2) Iris
3) Pupil
4) Lens
5) Retina

Question 2

What is the Cornea?

Answer 2

A circular, transparent protective tissue that projects forward and protects the eye

Question 3

What is the Iris?

Answer 3

The colored portion of the eye which adjusts the size of the pupil to regulate the amount of light entering the eye.

Question 4

What is the Pupil?

Answer 4

The dark portion in the center of the Iris. It allows light to enter the eye and stimulate the retina.

Question 5

What is the Lens?

Answer 5

A transparent, biconvex membrane that directs (refracts) light upon the retina.

Question 6

What is the Retina?

Answer 6

A complex, structured membrane that contains photoreceptor cells called rods and cones. Rods and cones are connected to nerve cells that transmit information to the brain via the optic nerve.

Question 7

What are the 3 types of vision?

PMS

Answer 7

Photopic - day OR bright/high light levels

Mesopic - dusk/dawn OR medium to low level light

Scotopic - night OR low light levels

Question 8

Describe Photopic vision.

Answer 8

• Vision used in daylight or when there is a high level of artificial illumination.
• The cones are primarily used. The rhodopsin is bleached out and rods become less effective.
• Characterized by sharp image interpretation and color vision.
• Best visual acuity: 20/20

Question 9

Describe Mesopic vision.

Answer 9

• Used at dawn, dusk or during full moonlight.
• Uses rods and cones.
• Characterized by decreased visual acuity and decrease in color perception.
• Best visual acuity: varies based on conditions.

Question 10

Describe Scotopic vision.

Answer 10

• Used under low light levels.
• Rods are primarily used and cones become ineffective.
• Characterized by a loss of color perception, visual acuity and detail.
• Best visual acuity - 20/200

Question 11

What are the visual deficiencies?

MANSHPR

Answer 11

• Myopia - nearsightedness (distant objects are not seen clearly)
• Astigmatism - unequal curvature of the cornea causes an out of focus condition when looking at things in 2 different planes (i.e. power poles vs power lines)
• Night Myopia - slightly myopic individuals experience visual difficulty at night when viewing blue-green light causing blurred vision.
• Surgical Procedures - PRK/LASIK
• Hyperopia - farsightedness (close objects are not seen clearly)
• Presbyopia - The lens of the eye becomes hardened (happens during the normal aging process) and could cause clouding of the lenses (cataracts).
• Retinal Rivalry - eyes trying to focus on two different things at the same time (like the HUD). Can cause pain.