Actions Of EOMs

Question 1

Ductions x4

Answer 1

Ductions = monocular movement

One eye moving about its centre of rotation

Classified by direction that anterior pole moves away from primary position

Assumed that sagittal axis and visual axis coincide

Question 2

Centre of rotation

Location

Answer 2

Virtual point about which the eye is assumed to rotate

Eye does not have a truly fixed centre of rotation due to soft nature of the fat and relative actions of muscles.

Location - 13-14mm behind corneal apex and 1.65mm nasally to geometric centre of eye

Question 4

Duction movements

Answer 4

Top - supraduction
Bottom - infraduction
Left - abduction
Right - adduction

Rotate left (towards ear) - excycloduction

Rotate right (towards nose) - incycloduction

Question 5

Duction
Reference point
Movement

Location

Answer 5

Supraduction movement = up
Infra movement = down
Adduction = in
Abduction = out
ALL Reference point = anterior pole (pupil)

Incycloduction = rotates in
Excycloduction = rotates out
BOTH reference point - superior pole (top of globe)

Line of action - a line joining the insertion to the origin of the muscle (except for superior oblique)

Question 6

Vergence movements

Convergence vs cyclovergence

Answer 6

Convergence : when visual axes of both eyes move nasally to fixate on a near object.

Cyclovergence : rotation of the upper pole of the eye relative to the other.

Question 7

Version movements

Answer 7

Both eyes move :
Up = supra-version
Down = infra-version
Left = laevo-version
Right = dextro-version