Extrinsic muscles and Amblyopia

The Fourth Affiliated Hospital of China Medical University

Ophthalmology Hospital of China Medical University

Extrinsic muscles

• The globles depend on the contraction and relaxation of extrinsic muscles to give rises coordinate movement. There are 4 recti and 2 oblique muscles in each eye.

Superior rectus muscle

Inferior rectus muscle

※ Motor function of extrinsic muscle

Main function The sccond function

internal rectus muscle abduction

Lateral rectus muscle outwards

Superior rectus muscle upwards abduction and intorsion

Inferior rectus muscle downwards adduction and extorion

Superior oblique muscle

intorsion downwards and outwards

Inferior oblique muscle extorsion upwards and outwards

Motor function of extrinsic muscle

internal rectus muscle

Lateral rectus muscle

Superior rectus muscle

Inferior rectus muscle

Superior oblique muscle

Inferior oblique muscle

Motor function of extrinsic muscle

Motor function of extrinsic muscle

Synergist and Sntagonist

• Synergist: simple eye

• Sntagonist: simple eye

Yoke muscles

primary position of eye

Right superior rectus muscleLeft inferior oblique muscle

Right lateral rectus muscle

Left internal rectus muscle

Right inferior rectus muscle

Left superior oblique muscle

Left superior rectus muscleRight inferior oblique muscle

Left lateral rectus muscle

Right internal rectus muscle

Left inferior rectus muscle

Right superior oblique muscle

Cardinal positions and yoke musclec

Strabismus

• Definition : both eyes can’t be fixed on the target simultaneously and the optic axes are divergent. one eye is fixing on the target and the other eye is deviating from it.

Strabismus

Check of strabismus

§ History taking§ Inspection§ Visual acuity examination § Refraction examination § Qualitative and quantitative examination of strabismus a. Cover test b. Corneal reflection of light point c. Triangular prism d. Examination of synoptophore e. Diplopia test f. Bielschowsky test g. Visual apperception test

Cover test

1.alternative cover test

2.cover-uncover test

Corneal reflection of light point

Corneal reflection of light point (Hirschberg) It is the most simple but commonly used method to determine

the angle of strabismus.

Triangular prism

The base of prism towards outside in esotropia, towards inside in exotropia.

Examination of synoptophore

Diplopia test

Analytical procedure of diplopia diagram

1.Determine the diplopia is horizontal or vertical at first.

2.In horizontal one, if it is crossed, it indicates exotropia . if it is ipsilateral, it indicates esotropia.

In vertical one, if the moved image is higher, indicating the paralytic eye is lower than the healthy one.

3.Determine the biggest direction of diplopia .

The crossed diplopia in right exotropia

Bielschowsky test

Visual apperception test

• Sensory adaptation is important to realize that pathological suppression ,ARC and amblyopia develop only in the immature visual system.

• Classification: (1) test of suppression (2) test of sensory fusion (3) test of stereopsis

Classification of strabismus

• 1. esotropia

• 2.exotropia

• 3.A and V patterns strabismus

• 4.vertical strabismus

Esotropia

• Concomitant esotropia (1)non-accommodative esotropia congenital esotropia (2)accommodative esotropia (3)part accommodation esotropia

• Paralytic esotropia

Esotropia

Concomitant esotropia

• Congenital esotropia: it is a constsnt esotropia with 6 month after birth. The angle of squint is equal and constant for seeing far and near. The strabismus can’t be corrected by glasses,with less relation to ametropia.

• Treatment: the operation could be done after treatment of amlyopia.

accommodative esotropia

For the hyperopia isn’t corrected ,over use of accommdation induces too strong convergence plus the hypofunction of fusion divergence to cause esotropia.

Part accommodation esotropia

Paralytic esotropia

Clinical findings: Diplopia and Vertigo, Compensatory head position, Limitation of

motion, 2nd angle of strabismus >1st angle of strabismusTreatment: Only when the etiology has been got of and optical therapy has

been given for 6 months, does the surgery be considered.

exotropia

Incidence of exotropia is smaller than one of esotropia, especially for children.

• Classification: (1) Intermittent exotropia: it hasn’t relation with ametropia

in general. The age of onset is often about 1 years old, but it is obvious at about 5 years old. It shows angle increase when fixating at distant.

(2) Constancy exotropia: incidence of constancy exotropia is smaller than one of Intermittent exotropia.

• Treatment: surgery

intermittent exotropia

A and V patterns strabismus

• An A pattern is present when a horizontal deviation shows a more convergent alignment in upgaze compared with downgaze.

• V pattern describes a horizontal deviation that is more convergent in downgaze compared with upgaze.

• A clinically significant A pattern is one that measures 10 . A clinically significant V pattern is one that △measures 15 . △

• Treatment: surgery

Vertical strabismus

• Incidence of it is small. Usually acquired when growing up.it is named according to topper eye.

Amblyopia

• Amblyopia is due to congenital or insufficient light stimulation entering the eye at critical period of development.

Classification of amblyopia

• Classification: (1)strabismic amblyopia (2)ametropia amblyopia (3) amblyopia by visual deprivation

• Treatment: the younger the age is ,the better the therapeutic effect becomes.

Nystagmus

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