Ocular Motility Flashcards
Define versions.
Binocular conjugate eye movements
Both eyes move in the same direction
Dextroversion-right
Levoversion- left
Supra/infraversion- up and down
Define ductions.
Eye movement tested under monocular conditions
ADduction, AB, incyclo, Supra
Define incomitant strabismus.
Strabismus where angle of deviation varies with angle of gaze
Define comitant strabismus.
Strabismus where angle of deviation is independent of angle of gaze
Define paralysis, paresis, palsy, contracture.
Paralysis: complete loss of muscle function
Paresis: partial loss of muscle function
Palsy: partial or complete loss of nerve function
Contracture: inability of contracted muscle to relax fully
Define primary and secondary angle of deviation.
Primary angle of deviation: deviation when fixating with unaffected eye
Secondary angle of deviation: deviation when fixating with affected eye
Incomitant deviations may be due to:
Paresis due to trauma
Mechanical restriction
Innervational deficiencies (3, 4 and 6)
What is the innervation and primary movement of medial rectus?
3
Adduction
What is the innervation and primary movement for lateral rectus?
6
Abduction
What is the innervation and primary, secondary and tertiary movement for inferior rectus?
3
Depression
Excycloduction
Adduction
What is the innervation and primary, secondary and tertiary movement for superior rectus?
3
Elevation
Incycloduction
Adduction
What is the innervation and primary, secondary and tertiary movement for inferior oblique?
3
Excycloduction, elevation, abduction
What is the innervation and primary, secondary and tertiary movement for superior oblique?
4
Incycloduction
Depression
Abduction
What angle does the superior and inferior rectus make with the median plane? How can this be used to test the function of these muscles?
23 degrees
Abduct by 23 degrees elevate to test superior, depress to test inferior. This can indicate normal function or a problem with the muscle
What angle does the superior and inferior obliques make with the median plane?
55 degrees (51-55 for IO)
ADduct by 55 degrees depress for superior oblique, elevate for IO to test for normal function
How can we test medial and lateral recti?
Adduction and abduction
What is defined as the diagnostic action field (DAF)?
The direction in which you have to look in order to test the muscle
DAF for RSR is up and to the right
When is the deviation caused by the restricted muscle the greatest?
When you look towards the DAF
Describe Sherrington’s Law.
Contraction os a muscle is accompanied by simultaneous and proportional relaxation of its antagonist
SO contracts, IO relaxes
Describe herring’s law of equal innervation. What are contralateral synergists?
Contralateral synergist are equally innervated when a movement is executed by both eyes (extra innveration is sent to the abnormally functioning muscle, overaction of contralateral synergist)
Contralateral synergists are pairs of muscles with the same DAF (RSR and LIO up and right)
What are the secondary sequelae of a muscle restriction (RLR)?
Overaction of the contralateral synergist (LMR)
Contracture of the direct antagonist (RMR)
Secondary inhibitional palsy of the contralateral antagonist (LLR)
2 overacting (LMR, RMR)
2 underacting (RLR, LLR)
What are developmental anomalies contributing to the etiology of incomitant strabismus?
Aplasia (incomplete development)
Paradoxical or anomalous innervation
Musculo-facial anomalies:
Incomplete differentiation of muscle sheaths
Malinsertions
Defective muscle attachments
Defective muscle sheaths
Fibrotic muscles
What is the acquired etiology of incomitant strabismus?
Trauma affect nerve or muscle
Vascular lesions affecting nerve
Space occupying lesion
Infective
Demyelinating disease
Myasthenia gravis (fatigue)
Metabolic disorders (diabetes, thyroid)
Iatrogenic (surgery, retinal detachment)
What muscle are commonly affected by entrapment?
IO or IR