Lecture 15 - Central Loss Flashcards
Ocular diseases affecting central VA include:
• ARMD - most common
• Macular holes
• Centrak serous retinopathy
• Cystoid macular oedeoma
• Toxic maculopathies
Functional effects of central field loss include:
• Acuity Loss
- Mainly impaired reading and face recognition
• Distortion
• Photostress
- Impaired dark and light adaptation
• Photophobia
- better vision at night
• Impaired depth perception
• Charles Bonnet Syndrome
- Visual Hallucinations after sudden loss of vision
- 13% of patients with AMD experience CBS
Charles bonnet syndrome: symptoms + management
• Incidence 10-15%
• Symptoms:
- Visual hallucinations: (Patterns, animals, plants, people…)
- Contributing factors: Cognitive defects, social isolation, sensory deprivation, anticholinergic drugs
• Management
- Explanation and reassurance
- increase lightning
- Improved visual function
- Reduce social isolation
- (Drug Tx)
When theres central field loss - which part of retina represents retinal locus?
• Macula is usually oculomotor reference
• If scotoma in only one eye, Px will not notice as will ignore with other eye.
• Central field loss only a problem if condition is bilateral
• If foveal involvement there will be severe acuity loss, and may try fixation using parafoveal area - at edge or scotoma
• This is defined as Preferred retinal locus
- will have lower VA furthest from fovea, we expect them to use edge of scotoma as closer to fovea = better VA
In early stages it central vision loss how is the scotoma seen by the Px:
• May not be aware of missing vision
• Vision appears distorted and patchy, coming and going
- Therefore acuity maybe worse than predicted
• Some Px may have learned to use PRL effectively (e.g children with central scotomas)
- Older Px are less likely to change preference and will perform uncoordinated eye movements
Treatment of field loss:
• Train Px to use optimum PRL all the time (can have diff for distance + near)
- ideally this will become oculomotor reference
• Should ideally be above or below the macula, as vertical training prevents scotomas caused by optic nerve physiology
How are scotomas detected in practice?
Amsler grids
• Correct viewing distance!
• Full Rx!
• MONOCULAR!!!
• Can you see the spot? All corners, all sides? Holes, blurry areas? Horizontal & vertical lines straight? Moving/shimmering lines or coloured areas?
Scanning laser ophthalmoscope or video fundus camera
- asking Px to fixate on target
Central field loss vs intact central field
Central field loss
- Finds newspaper headlines just as difficult to read as small print
- Has a variety of magnifiers of different strengths but can’t tell any difference between them
- The acuity improvement produced by magnification is less than expected, and often reaches a plateau
- Can often read a single letter (or the first letter of a line) and sometimes very short words, but cannot attempt long words
Intact central field
- Can see large print, but difficulties progressively increase as print gets smaller
- Accurately ranks magnifiers in terms of power and their usefulness for reading
- Progressive increases in magnification produce accurately predictable increases in reading acuity
- Reads single letters, short and long words equally easily
What is EV training?
• Eccentric viewing training teaches Px to adopt Steady eye strategy where the eye is kept still and the moving material is moved in front of eye. Good to use with magnifier.
- Move print, not eye
- Read letter by letter
- Different tasks (faces, clocks …)
- Speed reading software (RSVP)
- Scrolling text (MD EVreader)
How is EV training done
• Methods vary, usually done by trained professional not an optometrist
• Usually done for near tasks
• Practice sheets done first, the harder
- Not “real” text at first, as too frustrating
• Training done slow at first, e.g 5mins/day working up
• Use high mag lens such as 10-15x
- This is gradually reduced as Px improves
What is Prism relocation?
• Prism used to move retinal image out of scotoma + place on optimum PRL without need for Px to refixate
How is Prism relocation done in practice?
• Test monocularly
- Use trial lenses for distance Rx and add for working distance (20cm)
• Put 4^ Prism rotatable front cell of trial frame
- Ask px to rotate to find clearest vision for reading chart
- If no improvement change prism power
• When optimum prism found, optimising sphere
• Repeat other eye
• Prescribed yoked prism
• Most popular high success prism is base up - possibly placebo effect
Surgical treatment of field loss:
• Macular translocaton
- Involves detaching and rotating sensory retina on macular receptors so that theyre supplied by RPE, preserving macular function
What diseases cause central loss:
• Macular degeneration
• Best’s disease
• Stargadt’s disease
• Achromatopsia
• Cone dystrophies
What conditions cause peripheral vision loss?
Retinitis pigmentosa
Strokes (hemianopia)
Chorioretinitis
Glaucoma
Aniridia
Marfan’s syndrome
Retinal detachment
Leber’s amaurosis
combined loss - Coloboma
Optic nerve disorders e.g. optic atrophy
Optic dysplasia and hypoplasia strokes
