Visual Field Loss Flashcards
What effects can a brain lesion which causes hemianopia cause
- hemiplegia
- loss of higher visual functions
- occulomotor problems
- personality changes
Management strategies for visual field loss
- illumination and glare control
- optical methods
- visual field enhancement for sighting , minimised image produced
- VF enhancement for mobility where objects from the missing part of the field
Field enhancement for sighting
- reverse telescope
- amorphic lens
- concave lens
- convex mirror
Field enhancement for mobility
- mirror system
- prism system
- scanning
- electronic systems
What does an amorphic lens do
- minifies only in the horizontal plane,
- expands horizontal field
- preserves VA
- image distortion
Where should the edge of the prism be placed for prism systems
- edge of pupil/limbus
- prisms should be binocular
What are trifold lenses
- lens design is proposed to increase the FoV in Px with tunnel vision
- 2 prisms separated by vertical junction are fitted apex to apex
Disadvantages of prism system
- small VF
- VA 6/30
- jump a apex
- prism scotoma
- poor vision
Functional effects of central field loss
- acuity loss
- distortion
- photophobia
- depth perception
- colour vision
- Charles bonnet syndrome
What is Charles bonnet syndrome
Visual hallucinations after visual field loss
- patterns/animals/people
Contributing factors to Charles bonnet
Cognitive defects
Social isolation
Sensory depravation
Anticholinergic drugs
Management of Charles bonnet syndrome
- explaination and reassurance
- increase lighting
- improve visual function
Reduce social isolation
What is the occulomotor reference for eye movement
Fovea
What is preferred retinal locus
Point of parafoveal focus in presence of macular scotoma
Signs optimum PRL is not met, with central field loss
- newspaper headlines as difficult as small print
- can’t tell the difference between magnifiers of different strengths
- acuity improvement
- can read single letters/short words but not long words
- moves head
