tailieunhanh - Ebook Comprehensive ophthalmology (4/E): Part 2

(BQ) Part 2 book "Comprehensive ophthalmology" has contents: Ocular injuries, ocular therapeutics, lasers and cryotherapy in ophthalmology, systemic ophthalmology, community ophthalmology, clinical ophthalmic cases, darkroom procedures,. and other contents. | 13 CHAPTER 13 Strabismus and Nystagmus ANATOMY AND PHYSIOLOGY OF THE OCULAR MOTILITY SYSTEM Extraocular muscles Ocular motility BINOCULAR SINGLE VISION Definition Pre-requisites Anomalies STRABISMUS Definition and classification ANATOMY AND PHYSIOLOGY OF THE OCULAR MOTILITY SYSTEM NYSTAGMUS Physiological Sensory deprivation Motor imbalance EXTRAOCULAR MUSCLES A set of six extraocular muscles (4 recti and 2 obliques) control the movements of each eye (Fig. ). Rectus muscles are superior (SR), inferior (IR), medial (MR) and lateral (LR). The oblique muscles include superior (SO) and inferior (IO). Origin and insertion The rectus muscles originate from a common tendinous ring (the annulus of Zinn), which is attached at the apex of the orbit, encircling the optic foramina and medial part of the superior orbital fissure (Fig. ). Medial rectus arises from the medial part of the ring, superior rectus from the superior part and also the adjoining dura covering the optic nerve, inferior rectus from the inferior part and lateral rectus from the lateral part by two heads which join in a ‘V’ form. All the four recti run forward around the eyeball and are inserted into the sclera, by flat tendons (about 10-mm broad) at different distances from the limbus as under (Fig. ): Evaluation of a case Pseudostrabismus Heterophoria Heterotropia - Concomitant strabismus - Incomitant strabismus Strabismus surgery Medial rectus Inferior rectus Lateral rectus Superior rectus : : : : mm mm 6. 9 mm mm The superior oblique muscle arises from the bone above and medial to the optic foramina. It runs forward and turns around a pulley — ‘the trochlea’ (present in the anterior part of the superomedial angle of the orbit) and is inserted in the upper and outer part of the sclera behind the equator (Fig. ). The inferior oblique muscle arises by a rounded tendon from the orbital plate of maxilla just lateral to the .