Week 3 lecture 1- Visual disorders Flashcards
Information processing
Passive
Bottom-up process
Perception
Active
Both top-down and bottom-up
Can be disturbed
Representation
Knowing the position of things
Visual perception
Reconstruction of a distal stimulus based on a (weaker) proximal stimulus
Allows us to understand the environment and interact with it
Allows us to predict out environment
Types of neuro visual disorder (visual disorders after ABI)
- Lower order
-Hemianopia, achromatopsia
-assessed by optometrist or ophthalmologist - Higher order
-Visual agnosias
eg. prosopagnosia, balint’s syndrome
-assessed by neuropsychologist
prosopagnosia
Not being able to recognise faces that should be similar
still recognise people by the way they walk, talk, posture, clothing
Can be caused by damage to fusiform face area (ffa)
Alternative approach to causes of impaired visual perception
- Eyesight not optimal for circumstances (brain has to work harder)
- Quality of distal stimulus
- Something goes wrong in reconstruction process
Hemianopia symptoms
Visual:
restricted overview
feeling disoriented
bumping into objects or people; not seeing them in time
reading problems (not understanding what they read)
Non visual:
Anxiety
Mood disorders
Interventions for hemianopia
Adjustment of environment
Adaptation
Restoration of brain function
training of impaired brain function
compensation
distal and proximal stimulus
Distal: real world, far away
Proximal: what your eyes can see
Agnosia
Agnosia: inability to visually recognize or identify objects or people despite having ‘normal’ visual functions, memory, attention, etc
interventions for prosopagnosia
compensating- Look at voices, hair, clothing
Change distal stimulus
balint’s syndrome
Disorder of the reconstruction of the space around us
Types of balint’s syndrome
- Dorsal simultanagnosia
- Optic ataxia
- Oculomotor apraxia (‘sticky fixation’)
Dorsal simultanagnosia
- Not being able to ‘see’ two objects at the same time (i.e. not able to keep an active representation of more than one object at the same time)
- Not being able to relate objects in different spatial positions to each other
- Impaired spatial cognition
- Impaired spatial attention
Optic ataxia
- Seeing an object, but being unable to locate it, relate it to a certain position in space
- Disturbed direction of hand and arm movements to reach for an object (because the position of body with respect to the object is not
clear)
Oculomotor apraxia
- Not being able to make voluntary eye movements from one object to an other object (i.e. not being able to perform a visual search task)
- Bottom up processing of objects that ‘demand’ attention is still possible
Alternative to traditional approach to visual disorders
-Neurovisual disorders can be defined as ‘disorders of reconstruction’ of the distal stimulus
-agnosias and anopsias: One specific aspect of reconstruction is impaired or not taking place at all. Typically occurring after focal brain damage (e.g. ischemic stroke)
PD Visual problems
Difficulty reading
Blurred vision, trouble focussing
Problems with reduced contrast
Being blinded more often by (bright) light
Needing more light
Double vision, hallucinations, needing more time to see, participation
in traffic
Greater impact of visual problems in daily life compared to control
group
MS visual problems
Being blinded by bright light
Having difficulties adjusting to changes in light
and dark
Needing more light
Needing more time to see
Reduced contrast
