is eccentric fixation a monocular or binocular phenomenon
monocular
what type of patients have eccentric fixation
- only in strabismic amblyopic eyes, but not all amblyopic eyes
- almost always unilateral
what are 3 ways to classify eccentric fixation
- location (direction)
- magnitude
- stability
is the eccentric fixation associated with direction of strab?
yes
for example, XT will have temporal EF
is the EF magnitude associated with magnitude or strabismus
no
most EFs have a magnitude of
3 or less prism diopters
how does stability change from central to peripheral
generally more peripheral, less stable
what are the objective and subjective tests for EF
objective: visuoscopy
subjective: Haidinger’s brushes, Brock-Fivner AI Transfer
some important set ups for visuoscopy
- monocularly
- demo with non-amblyopic eye first
- project target into AE with dim illumination
- repeat several times for reliability
- easier if dilated
- high myopes can wear optical correction
how can you make it easier to appreciate Haidinger’s brushes
- decrease room illumination
- increase working distance
- viewing through high plus lens
- extra blue filter
how do you measure the magnitude of Haidinger’s brushes
at 40cm: 4mm= 1pd
what does the patient have to have for you to use Brock-Giver after image transfer test
normal correspondance
b/c after image tags foveal on NAE and cortical transfers to fovea of AE
how do you measure the magnitude of Brock-Giver after image transfer test
at 1m: 1cm=1pd
in the Brock-Giver after image transfer test: if the patient has NEF in his left eye, what would he report?
after image to the right of fixation point
normal fixation depends on the fovea having what 3 things
- best visual acuity (BVA)
- principal visual direction (PVD)
- zero retinomotor value (ZRMV)
what is visual direction and how does it work
- direction in subjective space associated with a given retinal receptor
- each retinal element localizes a stimulus in a certain direction
