Vision > Perception - Guest Lecture

True or false: OT does not diagnose visual disturbances, but they do link presence of visual impairment to functional performance impairments

true

What are some ways an individual can be affected by disability?

- increased anxiety

- decreased confidence

- decreased participation

- more passive

True or false: no matter how limited someone's vision is, they will still attempt to use vision to complete occupations

Visual acuity

the ability to see clearly

What is a way to assess visual acuity?

the Snellen chart

- can do this with both eyes, and then with one eye at a time

Visual motor

the alignment of our eyes and their ability to move - how well do our eyes work?

Visual perception

a complex process of determining the meaning out of what we see

- take in sensory information, and then it goes to the occipital lobe where it will be processed

True or false: the visual pathway does not cover a lot of real estate in the brain

false - it does. About 1/3- 1/2 of the brain is devoted to visual processing

True or false: vision conveys a tremendous amount of information in seconds

true - using the other senses requires more time to recognize at object

What is the concept of the hierarchical pyramid created by Mary Warren?

start with foundational concepts, and then continue to move on. All in place because then we are able to adapt to many things.

What are some others way to test visual acuity with younger, non-verbal children who don't know letters or numbers?

Visual acuity = how clear vision is. Test this with the Snellen chart that uses letters. Instead, can use a chart that has four shapes on it: a circle, house, apple, and square.

What is a visual field?

- being able to pick up objects in our periphery

- sides we can see about 30 degrees out

- up = we can't see as much

- lower = we can actually see pretty far down, and this helps with walking and to not trip

What are the different things related to oculomotor control?

alignment, fixation, saccades, tracking/smooth pursuits, accommodation, convergence

Ocular alignment

- when looking at the eye, the extrinsic eye muscles (controlled by CN III, CN IV, CN VI) all play a part in making sure the eye is aligned and centered.

- we can tell if the eye is misaligned by looking at the corneal reflection --> light will be reflected in the cornea, and it should be in the center

- misaligned when: eye inward (esotropic) or eye outward (exotropic)

What happens when CN III is impaired?

- innervates 4/6 extrinsic eye muscles, and we are specifically thinking about the medial rectus

- medial rectus = allows for the eye to move medially

- if this is impaired, the lateral rectus will be unopposed, allowing for the eye to be more lateral

What happens when CN VI is impaired?

- innervates the lateral rectus muscle, which helps to draw the eye laterally

- when there is an impairment, the medial rectus is unopposed, so the eye will sit more medial

What happens when CN IV is impaired?

- innervates the superior oblique muscle, which helps to draw the eye up and out

- when there is an impairment, the eye will sit down and in

- we can compensate with a head tilt due to potentially getting diplopia. tilt our head = goes away

Fixation

holding an image on the fovea

True or false: infants have good fixation even though visual acuity is not fully developed

true

Saccades

- quick eye movements from one fixation to the next (from one finger to the other)

- small saccades = used during reading

- large saccades = used during play and mobility

Why is reading considered using visual saccades?

once we develop more skills, we will jump over some words, which is what a saccade is

Smooth pursuits

- smooth eye movements

- make sure the object is about 18" away

- maintain fixation on the object while the object is moving and not moving the head with the eyes

- be sure to test the eyes together and separate

When does a person move away from moving their head and their eyes together, instead just using their eyes to follow?

6 months of age

Accommodation

- the ability to quickly focus the lens in order to foveate (bring into focus)

- near to distance quickly (example: looking at Ipad to quickly looking at the board)

- when there are small interruptions in the ability to quickly foveate occurring several times a day, this can be fatiguing!

Convergence

- bringing an object closed to one's face/looking at their own nose

- the eyes will turn inward as the object comes closer

- focusing and convergence occur simultaneously

- things to watch out for : eye loses visual fixation, and eye may break away

What are the normal developmental progressions?

- near vision before distance vision

- recognition of high contrast items develops before low contrast

- color before detail

- pictures before letters/numbers

Amblyopia

- decreased visual acuity in one eye that is often associated with misalignment

- not getting good information from the one eye, so the brain decides to not rely on that eye at all for information and only pay attention to the other eye. then the "impaired" eye is now misaligned due to not using it as much

- patching is prescribed to force the other eye to be used

Strabismus

- misalignment of the eyes

- inward = eso

- outward = exo

How is strabismus assessed?

perform the cover-uncover test; the client will focus on an object and will cover-uncover the eyes; the eye that is covered should remain aligned, and when the eye is uncovered there should be no saccade to fixate on object

What are some vision specific pediatric concerns?

- neonate: retinopathy of prematurity --> blood vessels grow too much and lift retina away from the eye and then there will be spots in vision, tears, and low vision

- cancer: accommodation

- abnormal tone: disorders such as cerebral palsy can cause high or low tone, which can affect the ciliary muscles that control constriction/dilation of pupil

- cortical visual impairment, cortical blindness

- optic nerve hypoplasia

How does high tone affect vision?

- see more clearly with near vision

visual clarity fluctuates

- can not be corrected by glasses

- may become accustomed to blurred image and loss of details

How does low tone affect vision?

- weak and delayed accommodation is common

- often seen in those with down syndrome

What is the most common visual field deficit in adult brain injury?

visual field deficit

True or false: compensations for visual field deficits can be spontaneous

false - they are learned; may not know that they even have a problem

What does a left visual field cut look like?

- first, will be the left visual field in both eyes

- we don't just see nothing --> brain can fill in what should be there due to cues and things we know.

Visual field deficit vs. neglect

- neglect = visual field deficit + inattention

- usually there is neglect of visual field, body, and environment

What do we do when an patient has diplopia?

- occlude what is the most important until the vision calms down

- put tape on the inside or outside of the glasses

- tape on glasses is considered a compensation, NOT a fix

What do we commonly see with concussions?

convergence insufficiency

What are some common visual impairments for the older adult?

- cataract

- glaucoma

- diabetic retinopathy-damaged retina

- macular degeneration

Cataract

cloudy lens; can't see well and looks dirty; can get this taken out

Glaucoma

increased intra-ocular pressure resulting in damage to the optic nerve

Macular degeneration

everything in the fovea drops out, and then now we are only left with peripheral vision

What are the two main types of OT intervention?

- remediation: change the person

- compensation: change the occupation and/or environment

What are some examples of compensations?

- increased the use of contrast or color

- decrease the pattern

- make use of less shadows and glare

- enlargement

- multisensory: add movement, sound