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 functionThe sccond function internal rectus muscleabduction Lateral rectus muscleoutwards Superior rectus muscle upwardsabduction and intorsion Inferior rectus muscle downwardsadduction and extorion Superior oblique muscle intorsiondownwards and outwards Inferior oblique muscleextorsionupwards 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

Synergist and Sntagonist Synergist: simple eye Sntagonist: simple eye

Yoke muscles primary position of eye Right superior rectus muscle Left inferior oblique muscle Right lateral rectus muscle Left internal rectus muscle Right inferior rectus muscle Left superior oblique muscle Left superior rectus muscle Right 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, 2 nd angle of strabismus >1 st angle of strabismus Treatment: 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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