Neurogenic palsies Flashcards
What is concomitant?
The angle of deviation is the same fixing either eye and in all positions of gaze. Not caused by neurogenic palsies.
What is incomitant?
The angle of deviation varies depending on the eye used for fixation and direction of gaze.
What are the causes of incomitance?
Primary causes:
-Neurogenic palsy e.g. third nerve oculomotor palsy
-Mechanical limitation e.g. physical limitation like ptosis
-Anisometropia this happens because of a difference in angle in fixing eyes
What are neurogenic palsies?
Nerve supply to muscle affected e.g one or more of the muscles in 6th or 3rd just the one muscle is affected
Palsies affect on VA
Palsies usually happen after vision is fully developed so they have normal VA. But if they have amblyopia previously this could cause reduced VA after a palsy.
What causes low VA after a palsy?
- Traumatic mydriasis
- Related to neurogenic condition e.g retrobulbar neuritis in MS
- If recent, can contribute to decompensation of longstanding palsy
- Co-incidental pathological cause
What are actions of the SR muscle
Elevation
Intorsion
Adduction
What are the actions of IR muscle
Depression
Extorsion
Adduction
What are the actions of the SO muscle
Depression
Intorsion
Abduction
What are the actions of the IO muscle
Elevation
Extorsion
Abduction
Muscle actions
Rad Sin
Superiors Intort = SIN Recti Adduct= RAD
Most patients fix with the
Unaffected eye
Characterstics
- Deviation in the primary position
- Fixing with unaffected eye (primary deviation)
- Fixing with affected eye (secondary deviation)
- Abnormal head posture (compensatory head posture) to avoid deviation
Abnormal head posture
Observe head turn/ tilt and elevation and depression
Longstanding
Observe in visual task and ask to put head straight straight and observe return to AHP looking for facial asymmetry – suggests longstanding
Types of head postures
Chin up/ down
Head turn/ tilt
Vertical/ torsion
Tilts to lower eye to use this
Torsion head tilt
E.g RE
Right eye intorts and left eye extorts thus if left extorsion is present, tilt right to match fellow eye to that eye position. Measure using PCT
Cover test recording
Ensure to record abnormal head posture; record first with AHP N+D then without AHP
Record size and type of deviation e.g.
-degree of incomitance
-differences in V Dev between N and D
-obliques larger at N, recti larger at D
Ocular movements observations
- Smoothness of movement during pursuit
- Head movements in child may indicate avoidance of affected movement
- Pupils, Lid position, changes
- Globe position, changes, Nystagmus
Further ocular movements observations
Check ductions and versions, interpret development of muscle sequalae, include the different eye movement systems e.g. smooth pursuit, saccades, OKN, VOR
BIOS terminology
Under action- reduced ocular rotation which improves on duction testing
Restriction- abnormal ocular rotation when movement doesn’t improve fully when testing ductions.
Limitation- abnormal ocular rotation
Assessment of BSV
Most patients with palsies have normal BSV but do not assume. They may have a previous deviation with suppression or AC, diplopia may occur with change in angle or traumatic loss of fusion
Measurement of palsies
- With / without AHP – latter more repeatable former only possible if longstanding
- With /without refractive correction - if indicated
- Near / distance
- Nine positions of gaze- PCT and Synoptophore
- Torsion- Synoptophore, Torsionometer and Double Maddox Rod
- Maddox Rod- Subjective where small vertical deviations
N.B. Expected deviation not always found due to a pre-existing deviation
Lees screen
Measurement of deviation in nine positions of gaze (up to 30°)
Compares one eye to fellow eye
Aids identification of affected eye and muscle
Aids differential diagnosis of neurogenic and mechanical limitations
Illustrates degree of concomitance
Used for monitoring patient
N.B Torsion can only be measured with a special adaptation
Not good for bilateral conditions
Field of BSV measurement
Records area in which BSV is maintained
Excellent record of patients symptoms
