Deviation in Incompetence in Business

Key Concepts

• Primary and Secondary Deviation

  • Primary Deviation: Deviation when fixing with the unaffected or sound eye.
  • Secondary Deviation: Deviation when fixing with the affected eye.
  • In concomitance, the deviation is the same regardless of which eye is fixing.

• Differences in Deviation Based on Fixation Eye

  • More deviation when the affected eye is fixing due to excessive innervation needed.
  • Example: Right lateral rectus palsy increases deviation when fixing with the affected eye.
  • Recent deviations show more distinction between primary and secondary deviations.
  • Long-standing deviations become more concomitant.

Neurogenic Palsies

• Deviation in primary position is opposite to the action of the palsied muscle.

  • Example: Adductor palsy results in esotropia due to unopposed ipsilateral antagonist.
  • Complex Example: Left superior oblique palsy causes elevation, adduction, and excyclorotation.

• Effects of Head Posture

  • Abnormal head postures can alter deviation.
  • Example: Head tilting to achieve binocular single vision (BSV).

Gaze Positions

• Deviation is greatest in the direction of action of the affected muscle.
• Least deviation in the direction opposite to the affected muscle's action.
• Example: For a vertical muscle palsy, deviation is greatest in its field of action.

Mechanical Restrictions

• Deviation may be minimal in primary position despite significant movement limitations.
• Mechanical restrictions can cause reversal of deviation direction.
  • Example: Reversal of hyper deviation in specific gaze positions.
• Contrast with neurogenic palsy:
  • In neurogenic palsies, deviation in primary position relates to the severity of the palsy.

Summary of Differences

• Neurogenic Palsies:

  • Secondary deviation > Primary deviation.
  • Deviation greatest in the direction of action of the palsied muscle.
  • Deviation in primary position opposite the action of the palsied muscle.

• Mechanical Restrictions:

  • Minimal deviation in primary position.
  • No direct relationship between limitation and deviation in primary position.
  • Likely to cause reversal of deviation.