341 Vision

sclera, uvea, retina

What are the 3 layers of the human eye?

3

How many layers comprise the human eye?

sclera

fibrous white outer layer of the eyeball, continuous with cranial dura mater; contains the cornea

sclera

What is the outermost layer of the eye? 

sclera

What layer of the eye does the cornea belong to?

dura mater

The sclera is continuous with what cranial meningeal layer?

cornea

transparent anterior portion of the sclera; lies in front of the iris and pupil

cornea, iris, pupil

The ____ lays in front of the ____ and ____. 

uvea

vascular middle layer of the eyeball, containing the choroid, iris, pupil, and lens

uvea

What is the middle layer of the eye? 

choroid, iris, pupil, lens

What four structures belong to the uvea? 

choroid

majority of the uvea; densely pigmented layer between the sclera and retina

iris

circular structure that forms the colored portion of the eye

pupil

circular opening in the center of the iris through which light enters

lens

portion of the uvea directly posterior to the iris which focuses light rights on the retina; has ability to change shape based on how near or far visual stimulus is

uvea

Which layer of the eye does the choroid belong to?

uvea

Which layer of the eye does the iris belong to?

uvea

Which layer of the eye does the pupil belong to?

uvea

Which layer of the eye does the lens belong to?

accommodation

process by which the ciliary muscle (innervated by CN III) contracts or relaxes to change the shape of the lens based on how near or far visual stimulation is

contraction

Does ciliary contraction or relaxation make the lens more convex to focus on nearby objects?

relaxation

Does ciliary contraction or relaxation make the lens flatter to focus on nearby objects?

retina

inner layer of the eyeball covering the posterior 2/3 of the inner eye; direct outgrowth of the diencephalon; contains the sensory receptors for vision (photoreceptors): rods and cones

rods, cones

What are the 2 types of photoreceptors found in the retina

diencephalon

The retina is a direct outgrowth of the ____.

retina

What is the innermost layer of the eye?

rods

photoreceptors specialized to receive peripheral visual input; function best in dim light; concentrated peripherally on retina

cones

photoreceptors specialized to receive colors and acuity; function best in bright light; concentrated centrally on retina

rods

Which photoreceptor functions best in dim light: rods or cones?

cones

Which photoreceptor functions best in bright light: rods or cones?

rods

Which photoreceptor is specialized to receive peripheral visual input: rods or cones?

cones

Which photoreceptor is specialized to receive colors and acuity: rods or cones?

peripheral, dim, colors, acuity, bright

Rods are specialized to receive ____ visual input and function best in ____ light, while cones are specialized to receive ____ and ____ and function best in ____ light.

false

True or false: rods and cones are distributed evenly on the retina.

rods

Which photoreceptor is concentrated peripherally on the retina: rods or cones?

cones

Which photoreceptor is concentrated centrally on the retina: rods or cones?

macula lutea

yellow circular part at the center of the retina that is important for central vision

fovea centralis

central part of the macula located directly in line with out visual axis; contains primarily cones and is the area of highest acuity on the retina

central

Are the macula and fovea important for central or peripheral vision? 

cones

What type of photoreceptors does the fovea centralis primarily contain?

optic disk

portion of retina where axons of retinal neurons, called ganglion cells, converge to leave the retina to become the optic nerve; contains no photoreceptors, so therefore there is a blind spot about 15 degrees lateral to the visual axis on each eye

ganglion cells

What are retinal neurons called?

false

True or false: the optic disk primarily contains cones.

true

True or false: the optic disk contains no photoreceptors.

macula lutea, fovea centralis, optic disk

Name the 3 structures of the retina.

optic disk

Which structure is responsible for the blind spot?

perceptual completion

process by which brain fills in the blanks of the eye’s blind spot

monocular

viewed with one eye

binocular

viewed with two eyes

stereoscopic vision

the ability to perceive three-dimensional depth using two eyes (binocular vision), where the brain combines two slightly different images (retinal disparity) to create a single, three-dimensional view

binocular, stereoscopic

Because we have ____ vision, we also have ____ vision, which aids in depth perception.

receptive field

location on (or beyond) body where application of an adequate stimulus causes a neuron to respond; can be spatially mapped in the CNS

visual field

visual surround; quantity of what one sees; region of space seen

retinal field

representation of outside visual field on retina

true

True or false: visual fields and retinal fields are both receptive fields.

visual field

Is the receptive field for vision typically referred to as the visual field or retinal field?

4

How many visual fields does each eye have (not including central and peripheral visual fields)?

temporal visual field, nasal visual field, superior visual field, inferior visual field

Name the 4 visual fields of each eye (not including central and peripheral visual fields). 

100º

About how large is the temporal visual field (in degrees)?

60º

About how large is the nasal visual field (in degrees)?

60º

About how large is the superior visual field (in degrees)?

75º

About how large is the inferior visual field (in degrees)?

quadrant

quarter of a visual field

central visual field

area directly around focal point and area of highest acuity; also called foveal vision, focal vision, central vision

foveal vision, focal vision, central vision

Name 3 additional terms used to describe the central visual field.

peripheral visual field

area outside of central visual field; not as good acuity, but good at movement detection; helps with balance, movement, coordination, and posture; also called ambient vision or peripheral vision

ambient vision, peripheral vision

Name 2 additional terms used to describe the peripheral visual field.

nasal hemiretina, temporal hemiretina

Name the 2 halves of a retina if a vertical line is drawn through the fovea.

superior hemiretina, inferior hemiretina

Name the 2 halves of a retina if a horizontal line is drawn through the fovea.

nasal hemiretina, temporal hemiretina, superior hemiretina, inferior hemiretina

Name the 4 retina fields created with vertical and horizontal lines drawn through the fovea.

right, left, inverted

The images of objects in the visual fields are ____-____ reversed and ____ on the retina.

nasal

Images present in the temporal visual field of the left eye fall on the ____ hemiretina of the left eye. 

inferior

Images present in the superior visual field of the left eye fall on the ____ hemiretina of the left eye. 

central

The ____ visual fields of both eyes overlap and are projected onto both retinae.

medial rectus (MR), CN III (oculomotor)

Which extraocular muscle and cranial nerve is responsible for the following eye movement: in (adduction)

superior rectus (SR), CN III (oculomotor)

Which extraocular muscle and cranial nerve is responsible for the following eye movement: up (elevation)

inferior rectus (IR), CN III (oculomotor)

Which extraocular muscle and cranial nerve is responsible for the following eye movement: down (depression)

inferior oblique (IO), CN III (oculomotor)

Which extraocular muscle and cranial nerve is responsible for the following eye movement: extorsion (external rotation) 

superior oblique (SO), CN IV (trochlear) 

Which extraocular muscle and cranial nerve is responsible for the following eye movement: intorsion (internal rotation) 

lateral rectus (LR), CN VI (abducens)

Which extraocular muscle and cranial nerve is responsible for the following eye movement: out (abduction)

conjugate

two eyes moving the same amount in the same direction; used to move an object’s image onto the fovea or to keep an object’s image on the fovea

vergence

two eyes moving in opposite directions

conjugate, vergence

Name the two general types of eye movements. 

conjugate

Which type of eye movement is used to move an object’s image onto the fovea or to keep an object’s image on the fovea? (conjugate or vergence)

saccades

fast, steplike conjugate movements that redirect gaze so a different image falls on the fovea

smooth pursuits

visual tracking; keeping an object’s image on the fovea

vestibuloocular reflex (VOR)

conjugate movement that helps keep image on fovea when head is moving

saccades, smooth pursuits, vestibuloocular reflex (VOR)

Name 3 types of conjugate movements.

vestibuloocular reflex

What does “VOR” stand for?

convergence, divergence

Name 2 types of vergence movements.

convergence

type of vergence movement in which both eyes adduct to focus on an object coming near to the body 

divergence

type of vergence movement in which both eyes abduct to focus on an object moving away from body

brainstem, cerebellum, cerebrum

Name 3 brain structures that contribute to the initiation and coordination of eye movements.

suprachiasmatic nuclei

hypothalamic nuclei that sends visual information about lightness/darkness to the pineal gland to regulate circadian rhythms

superior colliculi 

Which midbrain structure receives visual information related to eye movements? 

32

There is a minimum of how many cerebral cortex areas involved in vision?

12

There is a minimum of how many brainstem areas involved in vision?

anterior

Which component of the visual system (anterior or posterior) is more vulnerable to aging and traumatic brain injury (TBI)?

posterior

Which component of the visual system (anterior or posterior) is more vulnerable to perinatal and postnatal syndromes (such as shaken baby syndrome and periventricular hemorrhage), strokes, and traumatic brain injury (TBI)?

acuity

Visual ____ deficits are problems with the quality or clearness of vision.