Incomitant deviations

_ a deviation tha changes in magitude with direction of gaze (NOT W/ viewing distances)

• deviation = biggest in direction of max action of msc

1. Hering;s law of equal innervation - equal impulse sent to msc & contralateral synergist

2. Sherington's law- whenever an extraocular muscle receives a neural impulse to contract, its antagonistic muscle receives a signal to relax

• target = pen torch ( esp. to see corneal refllexes) + non acomodative

• for child = small toy

• tip of pen for px if uncomfortable ( can cause latent dev to decompensate.

technique

• 50cm

• head stationary + remove specs

• px reports any pain/dip (subjective) + observe you mvt ( objective)

• do 6 cardinal points then up and down ( doesnt isolate individual msc) OR H pattern

• alternating cover test at angle of gaze

• shows type and direction

• if ophoria, px wont report dip bz motility is not a dissociated test

• if tropia, px might supress = no reported diplopia

1. underaction of affected msc

2. overaction of contralateral synergist

3. overaction of ipsilateral antagonist

4. underaction of contralateral antagonist

Ad: spread of comitance = easier to manage to prism or surgery

to compensate for limited FOV of binocular single vision

head will point in direction of max action of affected msc to avoid eye turning in that direction.

type and direction should be noted: AHP turn,tilt,lift or chin depress

** straighten head before performing motility

AHP can be due to shyness, hearing impairment, arthritis, habit