wk11: BV - Strabismus 3 and 4 Flashcards
Where is fixation in patients with normal acuity?
always central
When might the patient not fixate centrally (i.e. with the macula)?
When the macula isn’t working properly (due to pathology or amblyopia)
Describe fixation when:
- amblyopia
- amblyopia but macula of deviating eye without motor superiority
A: may be central or unsteady
B: steady but eccentric
Where is the fixation in most amblyopic patients?
central
What is the purpose of Haidenger’s brushes? Are they used today?
subjective assessment of eccentric fixation (not used anymore)
List the 6 sensory aspects of strabismus
V.A Fixation Suppression Stereopsis Motor fusion Anomalouscorrespondence
How can we assess the steadiness and centrality of fixation?
Visuoscopy with direct ophthalmoscope
Explain the procedure for visuoscopy (4)
Use a target on opthalmoscope
Patient may need to be dilated for this
Patient looks at central target with bad eye (with good eye covered by px)
So their macula should be in the centre of the target when looking through the ophthalmoscope (unless it’s deviated)
How can we measure the amount of deviation away from fixation in visuoscopy?
Markings away from target in ophthalmoscope can be used for reference
What should you check before performing visuoscopy?
Cover bad eye first and check if patient can perform test with good eye, then if they can, you can then test the bad eye
Do patients with deviating strabismus respond to treatment such as occlusion?
No
How do Haidenger’s brushes work?
provides a polarised rotating target that only the macula can see which the child locates as being either straight ahead or off to the right or left, so it’s a subjective way of determining eccentric fixation
Do we use Haidenger’s brushes? Why/why not?
“this is only suitable for older children and we can use ophthalmoscope for younger so just use ophthalmoscope”
Describe how diplopia occurs
the non fixating eye will see the object of regard with receptors nasal to the macula and perceive it as being temporal
What is confusion and how does it work?
(different objects in same direction) is caused by
both macula seeing different objects but both perceiving them
as straight ahead
It’s also a psychic move with 50 base power
