Week 9: Visual System

Question 1

Rods

Answer 1

Black and White –> Peripheral vision

Question 2

Cones

Answer 2

Color –> Central vision

Question 3

Pathway of Vision

Answer 3

Visual information from the eyes travels through the optic nerve to the optic chiasm, where some fibers cross over while others continue on the same side. These split fibers form the optic tracts, which relay information to the lateral geniculate nucleus (LGN) in the thalamus. From the LGN, signals are sent to the primary visual cortex located in the occipital lobe, where the brain processes and interprets the visual information. Beyond this primary area, the brain integrates these signals with other sensory inputs and higher cognitive functions to form our perception of the visual world.

Question 4

Eye Lens accommodation

Answer 4

Adjusting the curvature of the lens
- Ciliary muscle flexion: ligaments loosen, curving the lens
- Ciliary muscle relaxation: ligaments tighten, making it flat

Lens flexibility decreases with age
- Cataracts surgery: artificial lens
- Curvature cannot be adjusted, leading to being far-sighted

Question 5

Glaucoma

Answer 5

Impaired filtration of vitreous humor, causing pressure buildup on periphery (Tunnel vision) Peripheral vision is lost

Question 6

Diabetic Retionathy

Answer 6

Prolonged high blood glucose damages small blood vessels
- Black dots

Question 7

Lesions to visual system

Answer 7

Impairment to visual fields depends on where is occurs along the visual processing system
Cut after chiasm on right side (loss of all vision in right eye)
Cut on chiasm in middle (Right visual field on left eye and left visual field on right eye)
Cut before chiasm on right side (Right visual field on both sides)
Cut at the bottom right (only a corner taken out on left side)

Question 8

Nystagmus

Answer 8

Repetitive, uncontrolled movements of the eye
- Caused by impairment to at least one of these
(Fixation, vestibulo-ocular reflex, and gaze-holding system (ability to hold gaze on an object)

Question 9

Amblyopia

Answer 9

Also known as “lazy eye”
- Patched placed over the good eye to force use of the lazy eye
- If not done early in life it can become permanent due to neurodevelopment and neuroplasticity

Question 10

Scotoma

Answer 10

Areas of blindness (One black spot at top corner)

Question 11

Peripheral Field Loss

Answer 11

AKA tunnel vision

Question 12

Glare Sensitivity

Answer 12

Inability to accommodate to change in lighting (can look blurry)

Question 13

Visual Field Cut

Answer 13

Field cuts involve partial blindness where the patient cannot see on the affected side.

Question 14

Optokinetic Reflex

Answer 14

Helps to hold images on the retina during stable and dynamic head movement (looking out the window of a moving vehicle)

Question 15

Visual Acuity

Answer 15

The ability to see visual detail

Question 16

Object Fixation

Answer 16

The ability to locate and focus on a stationary object or target (important for people with low levels of consciousness)

Question 17

Visual Pursuit/Tracking

Answer 17

The ability to lock onto and maintain fixation on a moving target across the whole visual field (Assessed with the X and the H test)

Question 18

Functional Acuity

Answer 18

The ability to see detail at both near and far distances
(i.e., does the person have visual deficits while performing functional tasks - reading a clock to tell time or finding clothes in a closet and then getting dressed)

Question 19

Diplopia

Answer 19

Double vision. The symptom of an ocular muscle imbalance

Question 20

Saccades

Answer 20

Quick precise eye movements made during visual scanning or a visual search (E.g., looking for a person in a crowded room)

Question 21

Accommodation

Answer 21

Allows for changing focal length (looking near to far or far to near)
Includes
- Changing the thickness of the lens
- Convergence of the eyes
- Pupillary constriction
Examples
- Driving and looking at road and speedometer

Question 22

Convergence

Answer 22

The ability of both eyes to move medially during a near task. Allows for reading.

Question 23

Visual Field

Answer 23

The space one is able to see when looking straight ahead
- Normal field of vision is approximately 160 degrees with both eyes

Question 24

Visual attention

Answer 24

The ability to visually direct attention within all visual fields

Question 25

Contrast sensitivity

Answer 25

Contrast sensitivity (CS) is the ability to perceive sharp and clear outlines of very small objects. It is also defined as the ability to identify minute differences in the shadings and patterns.

Question 26

Trochlear Nerve lesion

Answer 26

a unilateral trochlear nuclear lesion affects the contralateral nerve and superior oblique muscle, while a fascicular lesion affects the ipsilateral nerve and muscle

Question 27

Abducens nerve lesion

Answer 27

On exam, there is inability to abduct the affected eye. Abducens nerve palsy causes an incomitant esotropia due to the unopposed action of the antagonistic medial rectus muscle. The affected eye turns in toward the nose and is unable to abduct properly.

Question 28

Cone photoreceptors are responsible for _____ vision and are concentrated in the ____ portion of the retina

Answer 28

Color, Central

Question 29

Where do the medial portions of the optic nerve cross the brain hempisphere

Answer 29

Optic chiasm

Question 30

The ventral visual stream is responsible for _____ whereas the dorsal visual stream is responsible for _____

Answer 30

Perception (knowing); Action (doing)

Question 31

While the ciliary muscle of the eye is relaxed, the lens ligaments tighten. Which shape of the eye is the lens in?

Answer 31

Flat

Question 32

An inability to move the gaze of one eye medially suggest impairment to which cranial nerve

Answer 32

CN #3 Oculomotor

Question 33

An OTR has 2 clients with visual impairments
Clients A and B both have difficulty seeing in their left visual field. Client A is aware of the deficit and will turn their head more to see. Client B is unware of the deficit and will for example leave their left shoe untied.

Client A most likely has ____ and Client B most likely has a ____

Answer 33

Visual field cut; visual attention deficit

Question 34

An OTR is conducting an initial evaluation with diabetes. The outpatient complains of small black dots in their vision. The OTR refers the outpatient to an ophthalmologist for which of the following conditions?

Answer 34

Scotoma

Question 35

An OTR conducts a chart review with a client in acute care. The OTR notes that the client had a stroke that is impacting the right optic tract. Which of the following visual field losses should the OTR anticipate

Answer 35

3 (both left halves of visual field are affected)

Question 36

An OT student goes to fieldwork at a vision clinic. The OT student sees the OT administer an assessment where the client looks straight ahead at the therapists nose. The OT has a highlighter in their hand out of the clients field of view, and then moves the highlighter horizontally. The OT asks the client to let the OT know when they first see the highlighter come into view. Which of the following assessments is the OT most likely administering?

Answer 36

Visual Field Test

Question 37

An OTR observes a client trying to find utensils during a cooking task. The OTR notes that as the client scans the drawers and cabinets are disorganized and tend to undershoot or overshoot the visual target. This most likely indicates an impairment to which of the following.

Answer 37

Saccades