Unit 2 - Visual Perception Flashcards
Visual Perception
the total process responsible for the reception and cognition of visual stimuli including components of visual reception and visual cognition
functions of visual perception interaction
- Respond and adjust to retinal stimuli (requires anatomic and physiologic integrity)
- Move both the head and eyes to collect “raw” visual data (occulomotor and vestibule-ocular control)
- Effectively interpret visual information (visuoperceptual ability)
- Respond to visual cues through efficient limb movement (visuomotor ability)
- Accomplish integration of all these abilities
visual-receptive components
taking in visual information
Approximately 70% of sensory receptors in the human body are allocated to vision
Visual-receptive components depend on the integrity of anatomy and physiology of the eye structures (ie. cone, rods, pupil, optic nerve, etc).
visual fixation
the ability to maintain visual gaze on person or object. This is a prerequisite eye movement for higher level skills of tracking and scanning. Requires conjugate eye movements.
visual pursuits
visual tracking of a moving object, involves the continued fixation on a moving object so that the image is maintained continuously on fovea (located near the retina, it s the point of sharpest and clearest vision in the eye, it transmits the signal to the optic nerve).
• Typically seen as a child is following a ball throw to him/her, enable coordinated motor act of catching the ball.
• Pursuits are seen in infants 7 weeks of age (tracking parent), but is not fully developed until 16 to 18 years (Lane, 2005).
• Requires control of eye movements (oculomotor integrity)
visual saccades
visual scanning, the rapid change of visual fixation from one point in the visual field to the other. Seen in tasks of reading and copying, especially important for success in both tasks!
info about visual saccades
- The brain can’t handle all the visual information available to it, ¾ of the visual information available to the brain is ignored (Smith, 2014).
- When we read, we don’t take in large amounts of visual information
- In reading, the eyes “jump” from word to word so that when each word is fixated, it is processed rapidly and the next eye movement is planned.
- Saccadic eye movements start to develop during 2 to 5 months of age, but are typically inadequate until about 7 years of age. Many 5-year olds have difficulty performing saccadic eye movements accurately.
- During reading, we move our eyes from one fixation (word) to another fixation (word) by saccadic eye movements. When we move to the next word, the cognitive information continues, but the visual information should terminate (thus allowing for new visual information to be processed). ~75% of childrenwith reading disabilities have deficits with overlapping words (Smith, 2014):
How to spot a child with poor saccadic eye movement
Eye movements include head movements when reading
Frequently loses place when reading
Omits words when reading
Skips lines when reading
Is a slow reading, has to re-read lines that are missed
Poor reading comprehension
• A child in first grade only takes in about 45% of a word, pauses 224 times per 100 word, pauses for .33 seconds. (Vogel, 2015).
• Typically, a person can read 250 words per minute or about 4 words per second (Smith, 2014).
• During these short pauses of fixation, visual information is extracted and processed by the brain.
• by improving a child’s eye movement, you can help improve a child’s reading and copying speed and efficiency
acuity
the ability to discriminate the fine details of an object with clarity. 20/20 means that a person can perceive as small an object as an average person can perceive at 20 feet.
accommodation
– the ability of each eye to compensate for a blurred image. The process used to obtain clear vision (ie. to focus on objects at varying distances). Typically, only takes a split second for accommodation to occur.
binocular vision
The ability to mentally combine the images from the 2 eyes into a single perception. The 2 prerequisites for binocular vision include alignment of both eyes on object and the size and clarity of these 2 images are compatible. When this occurs, the brain can combine the 2 images into a single perception.
convergence and divergence
the ability of both eyes to turn inward toward the medial plan and outward from the medial plane.
Visual-Cognitive Components
the processing and interpretation of visual stimuli is a mental process involving cognition, which gives meaning to the visual stimulus.
visual attention
the selection of visual input
alertness
the child’s natural state of arousal
selective attention
the ability to choose relevant visual information while ignoring the less relevant information; it is conscious, focused attention
visual vigilance
the conscious mental effort to concentrate and persist at a visual task. The skill is exhibited when a child plays diligently with a toy or when writing a letter, completing homework.
divided or shared attention
the ability to respond to 2 or more simultaneous tasks. This is seen when a child is engaged in 1 task that is automatic while visually monitoring another task.