Special Techniques Flashcards
What are the advantages of fan and block?
Easy to perform
No extra equipment needed (if already have fan and block)
Clear for high astigmats
Good for amblyopic px’s and those with corneal opacities (hard to perform ret)
What are the disadvantages of fan and block?
Hard to distinguish small axis changes
Hard to distinguish clear axis line for low astigmatism
If you are unable to get the blocks equal on fan and block, what should you do?
Give lower cyl power
Why is fog added on fan and block?
Brings both focal lines in front of the retina (creating myopic compound astigmatism) which allows you to find axis of minus cyl meridian (as it is clearer).
When finding power, both meridians are slowly brought closer to each other and the retina.
Why does Mohindra ret need to be done in complete darkness?
To dilate pupils as much as possible, to create as much of a cycloplegic effect as possible
Also stops easy distraction of child?
Why would you do Mohindra ret instead of a cycloplegic refraction?
Px has had adverse reaction or side effects previously
Anxious child
Legal issues
Why is -1.25 removed from the Mohindra ret result?
Normal WD adjustment would be -2.00 at 50cm but a small amount of accommodation is stimulated (+0.75) so this is removed from the WD adjustment
What should the patient report during gross perimetry?
When the target is first seen and if it disappears again
What are the limitations of gross perimetry?
Only one level of stimulus, so subtle defects may be missed(smaller/dimmer stimulus needed to detect), or extent of field may be underestimated (if stimulus was larger/brighter, field may be larger)
If stimulus moved too fast, small or subtle defects may be missed.
What is the extent of the superior visual field?
60 degrees
What is the extent of the inferior visual field?
70 degrees
What is the extent of the temporal visual field?
100 degrees
What is the extent of the nasal visual field?
60 degrees
