Visual Perceptual Deficits

visual impairment

change in quality and amount of visual input to the brain; impacts how the brain processes and uses visual input; results from disease, trauma, aging

• neurological- TBI, concussion, PD, MS, AD

• limits occupational engagement, social isolation, risk for depression

visual field

fixated eye can detect visual stimulation in a specific part of the environment; photoreceptors and visual pathway take info into retina from a point of fixation

• factors: distance from eye, apparent size, stimulus duration, background lighting, intensity of stimulus, contrast, color, patient factors, adapting to light/dark

Visual pathway

Visual Streams

Vision and Lobes of the Brain

occipital: primary visual cortex, visual association cortex (analyzing orientation, position, movement, initiation of smooth pursuits, visual field loss)

temporal lobe- combines sensory info associated with the recognition and identification of objects (people, place things)

frontal lobe- saccades, attention

parietal lobe- locating objects, eye movement, drawing/constructing objects, neglect, movement through space

Warren’s visual perceptual hierarchy

oculomotor control- allow eyes to move smoothly, coordinated through pursuits, saccades, ability to accommodate and fixate, focus of target on fovea of retina (head movement, gaze shift, fixation); binocular vision

• impairments: diplopia, reduced depth perception, difficulty tracking, reduced fixating/localizing, strabismus, convergence insufficiency

visual field- amount of visual surroundings that can be seen when a person looks straight ahead; monocular peripheral vision and binocular cen

• impairments: hemianopia, quadrantopia, depends on lesion location where visual field deficit is

visual acuity- ability to see clear and precise images for small visual details

• impairments: difficulty focusing, damage to the retina, optic nerve, posterior cortical processing

Visual Attention and Scanning

focal/selective- distinguish visual details; used for object recognition and identification

ambient/peripheral- big picture, location of objects in the environment and proximity

• impairments: hemi-inattention (impaired vs lost, reactive vs processing, inattention to different sensory input contralateral from lesion), spatial bias, nonlateralized attention deficit, mental representation of space

Pattern Recognition

perceptual process of matching incoming visual stimuli with stored visual memories

visual memory

take in stimuli, retain details, store it for later retrieval

visual cognition

ability to use visual info to solve problems, make decisions, and complete planning and organizational tasks through mental manipulation

Form constancy

form, shape, and object is recognizable even when it changes in size, position, or is in a different environment

• clinical presentation: difficulty recognizing people wearing different clothing, difficulty following directions with pictures

figure ground perception

ability to distinguish foreground from background or differentiate an object from background

• clinical presentation: unable to sort/match socks while folding laundry, locating items in drawers, missing road signs or other obstacles when driving, locate toy in toybox

visual closure

ability to accuratly identify objects that are partially covered or missing

• clinical presentation: can’t identify traffic sign partially hidden behind a tree, difficulty locating objects in fridge that are partially hidden

visual organization

ability to group objects based on their identifying properties

• clinical presentation: poor spacing in handwriting, difficulty locating objects in the store

spatial orientation

ability to recognize that position of oneself or objects in relation to opposing positions, directions, movement, and environmental locations

• clinical presentation: letter/number reversal, spacing out writing

topographical orientation- ability to orient oneself within the environment and navigate

• clinical presentation: lost/wandering behavior

depth perception

visual ability to perceive relative distance

• clinical presentation: missing a step, missing the counter when setting things down, unable to catch a ball

visual discrimination

ability to identify unique characteristics of objects, shapes, colors, and people for comparison

• difficulty sorting

agnosias

visual agnosia: condition in which a person can’t interpret visual info

• see common objects and don’t know what it is, but can identify it with other senses like touch or smell

color agnosia: inability to recognize colors despite intact color perception, semantic memory for color, and color naming

• selective loss of associations between objects and color (can’t answer what color is a banana, name things that are red)

prospagnosia- inability to identify familar faces

simultanagnosia- inability to see more than one object or part of an object at the same time

metamorphopsia

objects or straight lines appear warped, distorted, or bent

OTs Role

Vision Screen

visual acuity- snellen eye chart for distance and near

accommodation- automatic adjustment of they eye for seeing at different distances; use near acuity chart and move until blurry

diplopia- double vision; note what quadrants are affected

pursuit- ocular motor skills of following a moving taret with head still; note lack of smooth moment, sluggish, overshooting/undershooting, double vision, pain

Vision Screen Assessments

Depth perception- stereo fly test

suppression- ability to disregard info from one eye through natural adaptation to make sense of info received

• frequently following prolonged double vision. red/green activities

Treatment approaches

remediation- preferred as first measure when they show potential for improvement, awareness of limitations, ability to receive feedback

• scanning/tracking to increase strength of eye muscles, increase in complexity, repeated practice, building confidence

• not affective for decreased acuity

compensation- internal/external strategies to improve performance; maximize function and safety

adaptation- change the environment or task demands to increase safety and function

• adjusting placement/intensity of lighting, increased contrast, adjust print size

compensation + adaptation- when remediation is not effective; introduce in VFD, use first when safety is at risk

visual acuity eval and intervention

observe function, especially reading

• screen high and low contrast acuity

• use best corrected vision for refractive errors

• measure person’s ability to identify progressively smaller letters/numbers/symbols

intervention: clean and prescribed glasses→referral to optometrist/ophthalmologist

• increase contrast, reduce patterns, good lighting, enlarge items, structured/predictable environment

Oculomotor eval and intervention

obtain visual history, listen to complaints, observe eye movements (pupil asymmetries, eyelid function, eye position)

• track moving target vertically, horizontally, diagonally

• track convergence with moving target towards nose

• diplopia- access each eye covered/uncovered for deviation

intervention- education on visual stress, identify triggers, environmental mod (contrast, increase size, reduce pattern, lighting), habits/routines

• under the supervision of eye physician: occlusion, prisms and lenses, eye exercises, surgery

Visual field eval and intervention

visual attention/scanning eval

first eval for aphasia, motor impairment, visual acuity, oculomotor, visual fields

• observe visual search task while monitoring for organized search strategies (L to R, top to bottom, symmetrical search of both sides), sustained visual search or drifting off, locate targets accurately

• cancellation tests: lines, rows, numbers, symbols; record time to complete and accuracy

intervention: modification (focus on environmental and task mod; minimize patterns, increase environment structure); compensation (visual scanning strategy, interact physically with target, conscious attention to detail, lighthouse)

Patching

quick, effective, inexpensive tool to decrease unilateral inattention; occluding one ye facilitates attention and visual saccades to contralateral side

• caution: studies found that once removed, did not translate into function

• hemi field patching demonstrated greater improvements in functional independence

Pattern recognition intervention

skills required in form constancy + figure ground perception + visual closure + visual organization + spatial orientation

• reduce visual stimulation and overlapping objects; change spatial arrangements, slow down processing times, proper scanning strategies, multi sensory techniques

• laundry sorting: form piles of clothes by type, sort by color, search for specific clothes using a L-R top-bottom scanning strategy

visual perceptual screening

unilateral inattention screening

depth perception screening

Functional Therapy Activities for Perceptual Deficits