Vision & Perception

8.1.4

You are working in an adult day center clinic with a 79-year-old client who is diagnosed with legal blindness. With which of the following does your client likely present? SELECT ALL THAT APPLY.

a. Central visual acuity of 20/200.

b. Horizontal visual field cut of each eye 10 degrees from center.

c. Pelli-Robson Contrast Sensitivity score of 2.0.

d. Esotropia.

a. Central visual acuity of 20/200.

b. Horizontal visual field cut of each eye 10 degrees from center.

You are working in a community-based vision care center with a 91-year-old client with advanced primary open-angle glaucoma. With which of the following does your client likely present? SELECT ONE.

a. Loss of central vision.

b. Increased intraocular pressure.

c. Sensitivity to glare.

d. Retinal edema.

b. Increased intraocular pressure.

You are working in an outpatient pediatric clinic with a 4-yer-old client who has autism spectrum disorder and does not attend to faces. Which of the following do you suspect to be damaged in your client? SELECT ONE.

a. lateral geniculate nucleus

b. pretectum

c. hypothalamus

d. superior colliculus

d. superior colliculus

You are working in a skilled nursing facility with a 54-year-old client who sustained a stroke of the posterior cerebral artery, primarily affecting the ventral stream. With which of the following does your client likely present? SELECT ALL THAT APPLY.

a. impaired visual attention

b. prosopagnosia

c. hemi-inattention

d. limited ability to interpret facial expressions

a. impaired visual attention

b. prosopagnosia

d. limited ability to interpret facial expressions

You are working in an outpatient occupational therapy clinic with an 88-year-old client who presents with right homonymous superior quadrantanopsia due to a brain tumor. Which of the following structures do you suspect to be most likely affected? SELECT ONE.

a. left temporal fibers of the optic radiation

b. right parietal fibers of the optic radiation

c. optic tract

d. optic chiasm

a. left temporal fibers of the optic radiation

low vision

visual impairment that cannot be corrected by medical or surgical intervention but is severe enough to interfere with ADL performance (Warren, 2020)

legal blindness

o not a medical condition, but rather, a legal one o allows for eligibility for services (vocational training, rehabilitation, education, disability benefits)

o people usually have some degree of usable vision or light perception

o distance acuity of 20/200 or poorer in the better eye, even with correction

o widest diameter of the visual field 20 degrees or less

OT Role

• assess occ performance to identify environmental and occupational modifications to maximize independence

• interventions:

  • educate on effect of low vision on occ, prep for pregression

  • training and edu of optical devices

extraocular muscles

¡ Superior rectus (CN-III) – elevation

¡ Inferior rectus (CN-III) – depression

¡ Medial rectus (CN-III) – adduction

¡ Lateral rectus (CN-VI) – abduction

¡ Superior oblique (CN-IV) – intorsion

¡ Inferior oblique (CN-III) – extorsion

strabismus

Misalignment of the eyes due to weakness of extraocular muscles

esotropia

deviation in nasal direction as a result of weak lateral rectus

exotropia

deviation in temporal direction as a result of weak medial rectus

hypertropia

deviation in superior direction as a result of weak inferior rectus

hypotropia

deviation in inferior direction as a result of weak superior rectus

diplopia

double vision

stereopsis

= normal 3-dimensional depth perception

¡ Diplopia results in disruption of stereopsis because eyes are not conjugate (looking in same direction) and send differing images to brain

¡ Brain compensates by identifying a dominant eye

¡ Diplopia is a perceptual condition that may be a result of a motor impairment

cornea

clear, outermost portion; protects eye from particulates and ultraviolet radiation; refracts light onto lens.

sclera

connective tissue that constitutes white parts of eye

iris (CN-III)

colored part of eye; responds to light via photopupillary response.

pupil

opening at center of iris

lens

biconcave structure that refracts light to focus image

aqueous humor

nourishes lens and eliminates waste

ciliary muscles

contracts to control shape of lens

vitreous chamber (posterior cavity)

filled with gel-like substance to maintain shape of eyeball

retina

posterior surface of eyeball; rods (low illumination vision, peripheral vision, sense motion); cones (detect color, central vision, fine detail visual acuity)

macula

central vision (high concentration of cones)

fovea centralis

very center of macula, only cones (no rods)

cataracts

¡ Clouding of the lens

¡ Reduced night vision (changes in contrast sensitivity)

¡ Increased glare

¡ Seeing halo around lights

axial length

distance from cornea to retina

myopia

(near sightedness) – axial length is longer than focal length, resulting in blurred distance vision

hyperopia

(far sightedness) – axial length is shorter than focal length, resulting in blurred near vision.

presbyopia

Stiffening of the lens, resulting in difficulty with accommodation (blurred vision)

astigmatism

multiple focal points, resulting in blurred vision.

glaucoma

Group of conditions that damage the optic nerve due to abnormal pressure in the vitreous chamber

¡ Loss of peripheral vision

age-related macular degeneration (ARMD)

¡ Dry ARMD (80%): thinning of macula

¡ Wet ARMD (20%): abnormal growth of blood vessels in macula

¡ Blurring of central vision

¡ Difficulty seeing faces, reading, driving, cooking

cortical pathway

¡ Optic disc

¡ Optic nerve (CN-II)

¡ Optic chiasm

¡ Optic tract

¡ Lateral geniculate nucleus

¡ Superior colliculus

¡ Pretectum

¡ Hypothalamus

¡ Parietal optic radiation

¡ Temporal optic radiation

¡ Primary visual cortex

¡ Secondary visual cortex

¡ Dorsal stream

¡ Ventral stream

eye dominance

¡ Dominant eye is the eye one uses for visual fixation.

¡ Generally follows handedness; most people are right eye dominant.

¡ Provide client with a cardboard with a hole in it or a cardboard tube; instruct them to view an object

. ¡ Do not tell them what you are doing (checking eye dominance).

¡ Observe which eye they hold the cardboard up to.

visual acuity

Distance: >40 inches (e.g., reading street sign, watching television, recognizing faces) ¡ Intermediate: 20 to 40 inches (e.g., viewing computer screen, viewing dashboard)

¡ Near: 13 to 16 inches (e.g., reading, writing, dialing on a cell phone)

¡ Snellen chart

¡ LEA Numbers Intermediate Acuity Test Chart

contract sensitivity

¡ Ability to perceive minute changes in shading and patterns

¡ Closely associated with reading, mobility, driving

¡ Pelli-Robson Contrast Sensitivity Chart

o 2.0 normal contrast sensitivity

o 1.5 impairment

o <1.0 disability

¡ LEA Numbers Contrast Sensitivity Chart

central and peripheral visual field

¡ Ability to see objects and avoid obstacles

¡ Test in four quadrants (superior left and right; inferior left and right)

¡ Finger counting method

¡ Confrontation Test

¡ Amsler Grid

o 50 degrees nasal and superior o 90 degrees temporal o 60 degrees inferior

stereopsis (depth perception)..

¡ Binocular vision

¡ Remember that if the gaze is not conjugate, depth perception will be impacted.

¡ Titmus Stereopsis Test

smooth pursuits (tracking)

Ability to track moving objects with relatively smooth extraocular movements.

¡ Conjugate gaze

¡ Tongue depressor with stimulus held 16 inches from face

¡ Circumscribe circle, two rounds in clockwise direction, two rounds counter-clockwise

¡ Move about 4 seconds per round

¡ Note number of rotations client is able to complete

saccades

¡ Ability to shift gaze between two objects

¡ Useful in reading, obstacle avoidance

¡ Red/green stimuli

¡ Held 16 inches from face, 16 inches apart

¡ Have client complete five round trips

visual perception

Motor-Free Vision Perception Test –Vertical (MVPT-V)

o Spatial relationships o Figure-Ground discrimination o Visual discrimination o Visual closure o Visual memory

Scanning

¡ Ability to use vision to search for something in a systematic manner

o Letter Cancellation Test o Bells Test o Star Cancellation Test

¡ Hemi-inattention

¡ Visual field cut

¡ Cognitive organization

spatial relations

Ability to recognize relationships between objects in space

o Schenkenberg Line Bisection Test

¡ Presence of hemi-inattention or visual field cut

reading performance

o Reading speed, fluidity

o Consider illumination, text characteristics (font type, spacing)

writing performance

o Have client write a short paragraph from dictation

o Observe posture, head position, prehension pattern, legibility, quality of writing (drift, spacing)

OT Interventions

¡ Optical devices (magnifiers) ¡ Illumination (task lighting) ¡ High contrast markers ¡ Tactile markers ¡ Mainsteam technology

optic disc

where optic nerve synapses with retina; blind spot

optic nerve (CN-II)

lesion results in ipsilateral monocular vision loss

optic chiasm

where optic nerves decussate; objects in left visual field go to right hemisphere

optic tract

after decussation; lesions result in contralateral homonymous hemianopsia

lateral geniculate nucleus (thalamus)

relay station for visual information

superior colliculus (mesenceph/tectum)

processes visual info & coordinates oculomotor contro

pretectum

(mesenceph) – photopupillary response

hypothalamus

circadian rhythm for sleep-wake cycle

parietal (medial) optic radiation

contralateral homonymous superior quadrantanopsia

temporal (lateral) optic radiation

contralateral homonymous inferior quadrantanopsia

primary visual cortex

receives and processes visual information

secondary visual cortex

analyzes visual information for color, pattern complexity, object recognition/orientation

dorsal stream

spatial orientation, depth perception, location/movement of objects in space, impaired visual tracing, hemi-inattention (“where” of an object)

ventral stream

object recognition, reading text, learning/remembering objects; lesions result in impaired visual attention, prosopagnosia, inability to interpret facial expressions.