Visual Perceptual Functions and Skills

Visual Acuity

• ability to see small visual details

• keenness or sharpness

Fovea

• part of the retina which has the highest visual acuity

High-contrast acuity

• can be either distance acuity or near acuity

• measure how clearly you can see details with a high level of contrast

Myopia

• nearsightedness

• foreground is clear, background is blurry

Hyperopia

• Farsightedness

• Background is clear, foreground is blurry

Astigmatism

• abnormal curvature of cornea

• causes lights to be seen as dispersed

Presbyopia

• age-related loss of ability of eyes to focus on near objects

• middle- to older-aged adults to read at arm’s length rather than near their eyes

40s

• age when presbyopia onsets

Cataract

• causes blurry vision

• due to clarity of lens

Visual Field

• external world that can be seen when we look straight

• boundary of what is seen while looking straight ahead

Hemianopia

• loss of vision on half of the visual field

Quadrantanopia

• loss of ¼ quarter of the visual field

Homonymous Hemianopsia

• loss in same half of visual field for both eyes

• changes in head position when viewing objects within field

Visual Scotoma

• Blind or blurry spots

• reduced vision in some areas

Glaucoma

• tunnel vision

• loss of peripheral vision

Macular Degeneration

• loss of central vision

Diabetic Retinopathy

• dark floating spots in visual field

Perimetry

• process of measuring the visual field

Confrontation Test

• static targets are placed on four quadrants

• moving targets are placed along all quadrants

Eye Alignment

• eyes point to the same direction

Foveation

• position the fovea towards the object of interest

• necessary to maintain focus on a visual target especially during motion

Fixation

• ability to maintain gaze on a static target

Smooth Pursuits or Tracking

• ability to maintain continued fixation on a moving target

Saccades

• ability to rapidly and accurately shift vision from one point to another

Accommodation

• ability of the eyes to adjust its focus to see objects at different distances clearly

Binocular Vision

• depends on good eye alignment and ability of eyes to work as a team

• allows sensory fusion

Strabismus

• misalignment of the eye

Diplopia

• Double vision

Convergence Insufficiency

• eyes drift outward when looking at near objects

Nystagmus

• rapid, uncontrollable eye movements

Visual Attention

• ability to observe objects closely and carefully

• ability to ignore irrelevant sensory input and random thoughts

Visual Scanning

• motor respoinse to the desire to shift visual attention from one target to another

• accomplished using saccadic eye movements

Hemi-inattention

• loss of ability to attend, respond, or react to sensory stimuli

• spatial bias to the unattended side

• difficulty forming a mental representation of the affected side

Unilateral Neglect

• broader category of disorders that refers to the failure to detect, report, or respond to stimuli on affected side

Sensory

• Unilateral Neglect

• not aware of the visual, auditory, or tactile stimuli on the affected side

Motor

• Unilateral Neglect

• impaired initiation and execution of movements on the affected side

Representational

• Unilateral Neglect

• impaired ability to create mental visualizations of a task, action, or environment

Personal

• Unilateral Neglect

• lack of awareness of the affected side of the body

Spatial

• Unilateral Neglect

• failure to respond to stimuli in the space of the affected side

Peripersonal Space Visual Search

• assessment of attention and scanning at close range

• line bisection, single-letter cancellation, design copy, draw a clock

Extrapersonal Space visual search

• assessment of attention and scanning at large environment

Visual Perception

• gateway to cognition

• ability to interpret sensory information from the environment and process it in the brain’s cognitive centers

Visual Cognition

• ability to manipulate and integrate visual input with other sensory information to complete cognitive functioning

Pattern Recognition

• Identifying the most salient features of an object

• distinguish an object from surroundings

Visual Discrimination

• ability to distinguish distinctive features and know if a stimuli is different or same as others

Visual memory

• create and retain picture of an object in the mind’s eye

  • integration of visual information with various experiences

Visual Sequential Memory

• ability to recall a series of visual stimuli

Visual Form Constancy

• ability to recognize objects despite differences in orientation or detail

Visual figure ground

• ability to differentiate foreground and background forms and objects

• ability to separate essential data from distracting surrounding data

Visual closure

• ability to identify objects from incomplete presentations

Visual Spatial Relation

• orientation of one object to another object

Position in Space

• orientation of an object to oneself

Stereopsis or Depth Perception

• ability to determine the relative distance between objects and figure

Topographic orientation

• ability to determine location of objects and route a location

Agnosia

• inability to identify an object through visual means

Color Agnosia

• inability to remember and recognize specific colors of common objects

Color Anomia

inability to name colors of objects

Metamorphosia

• visual distortion of objects, such as physical property of size and weight

Prosopagnosia

• inability to recognize and identify familiar faces

Simultagnosia

• inability to recognize and interpret a visual array as a whole