Neurogenic palsies

Question 1

What is concomitant?

Answer 1

The angle of deviation is the same fixing either eye and in all positions of gaze. Not caused by neurogenic palsies.

Question 2

What is incomitant?

Answer 2

The angle of deviation varies depending on the eye used for fixation and direction of gaze.

Question 3

What are the causes of incomitance?

Answer 3

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

Question 4

What are neurogenic palsies?

Answer 4

Nerve supply to muscle affected e.g one or more of the muscles in 6th or 3rd just the one muscle is affected

Question 5

Palsies affect on VA

Answer 5

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.

Question 6

What causes low VA after a palsy?

Answer 6

• 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

Question 7

What are actions of the SR muscle

Answer 7

Elevation
Intorsion
Adduction

Question 8

What are the actions of IR muscle

Answer 8

Depression
Extorsion
Adduction

Question 9

What are the actions of the SO muscle

Answer 9

Depression
Intorsion
Abduction

Question 10

What are the actions of the IO muscle

Answer 10

Elevation
Extorsion
Abduction

Question 11

Muscle actions

Answer 11

Rad Sin
Superiors Intort = SIN Recti Adduct= RAD

Question 12

Most patients fix with the

Answer 12

Unaffected eye

Question 13

Characterstics

Answer 13

• 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

Question 14

Abnormal head posture

Answer 14

Observe head turn/ tilt and elevation and depression

Question 15

Longstanding

Answer 15

Observe in visual task and ask to put head straight straight and observe return to AHP looking for facial asymmetry – suggests longstanding

Question 16

Types of head postures

Answer 16

Chin up/ down
Head turn/ tilt
Vertical/ torsion

Tilts to lower eye to use this

Question 17

Torsion head tilt

Answer 17

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

Question 18

Cover test recording

Answer 18

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

Question 19

Ocular movements observations

Answer 19

• Smoothness of movement during pursuit
• Head movements in child may indicate avoidance of affected movement
• Pupils, Lid position, changes
• Globe position, changes, Nystagmus

Question 20

Further ocular movements observations

Answer 20

Check ductions and versions, interpret development of muscle sequalae, include the different eye movement systems e.g. smooth pursuit, saccades, OKN, VOR

Question 21

BIOS terminology

Answer 21

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

Question 22

Assessment of BSV

Answer 22

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

Question 23

Measurement of palsies

Answer 23

• 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

Question 24

Lees screen

Answer 24

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

Question 25

Field of BSV measurement

Answer 25

Records area in which BSV is maintained
Excellent record of patients symptoms