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Ophthalmic Injuries
Published in Ian Greaves, Keith Porter, Jeff Garner, Trauma Care Manual, 2021
Ian Greaves, Keith Porter, Jeff Garner
The upper lid should be everted in order to check for foreign bodies. This should not be attempted if the eye is known to be perforated. Eversion of the upper lid should be carried out in stepwise fashion: Ask the patient to look down.Grasp the lashes between the thumb and the forefinger.Place a cotton bud at the top of the tarsal plate (10 mm from the lid margin).Push the cotton bud down and pull the lashes up; the upper lid should then evert. The iris should be flat and have a round pupil at its centre. A distorted iris or pupil indicates significant damage to the anterior segment of the eye. Blunt trauma can result in a dilated pupil after rupture of the sphincter pupillae muscle although occasionally blunt trauma will cause miosis (pupil constriction). The presence of blood in the anterior segment indicates damage to the iris, lens, ciliary body or drainage angle; this is a hyphaema (Figure 15.2).
The nervous system
Published in Peter Kopelman, Dame Jane Dacre, Handbook of Clinical Skills, 2019
Peter Kopelman, Dame Jane Dacre
The abducens nerve innervates the lateral rectus and the trochlear nerve innervates the superior oblique muscle. All the other external ocular muscles, the sphincter pupillae (muscle of accommodation) and the levator palpebrae are supplied by the oculomotor nerve. A simple way to remember the muscle innervation is LR6SO4 – Remainder 3: lateral rectus = abducens (cranial nerve no. 6), superior oblique = trochlear (cranial nerve no. 4) and the remainder = oculomotor ( cranial nerve no. 3).
Head and Neck
Published in Rui Diogo, Drew M. Noden, Christopher M. Smith, Julia Molnar, Julia C. Boughner, Claudia Barrocas, Joana Bruno, Understanding Human Anatomy and Pathology, 2018
Rui Diogo, Drew M. Noden, Christopher M. Smith, Julia Molnar, Julia C. Boughner, Claudia Barrocas, Joana Bruno
The oculomotor nerve (CN III) (Plate 3.14) innervates five ocular muscles (see Section 3.4.5 for details about the extraocular muscles). The superior division of the oculomotor nerve logically innervates the two more superior muscles—levator palpebrae superioris that elevates the eyelid and the superior rectus that elevates the eye. The inferior division of the oculomotor nerve innervates the inferior rectus that depresses the eye, the medial rectus that adducts the eye, and the inferior oblique that elevates and abducts the eye because it runs to the posterolateral portion of the inferior surface of the eye. The oculomotor nerve carries with it the axons of parasympathetic neurons located near its somatic motor neurons. These axons leave the oculomotor nerve to synapse in the ciliary ganglion in the orbit. Postganglionic fibers enter the eyeball and travel to the iris, where they cause contraction of the sphincter pupillae muscle, thereby constricting the pupil.
Amplitude of Accommodation in Patients with Multiple Sclerosis
Published in Current Eye Research, 2019
Bekir Küçük, Mehmet Hamamcı, Seray Aslan Bayhan, Hasan Ali Bayhan, Levent Ertuğrul Inan
When the target distance is changed, the lens power must be altered to clearly view it; this is known as ocular accommodation.25 The accommodation reflex starts in the retinal ganglion cells with the light reflex. These impulses are sent through the optic nerve, the optic chiasma, and the optic tract. Most optic tract fibers go to the pretectal area, although some fibers synapse with the second-order neurons in the lateral geniculate nucleus of the thalamus. Then, second-order neurons carry the impulses through the optic radiation to the visual cortex. Impulses pass from the visual cortex to the prefrontal cortex, and fibers pass through the internal capsule to reach the midbrain. Then, the fibers in the midbrain synapse with the oculomotor nucleus and the Edinger-Westphal nucleus.26 The motor fibers are carried by the oculomotor nerve from the oculomotor nucleus to the medial rectus muscle, where both eyes converge. The efferent fibers of the Edinger-Westphal nucleus (which is the parasympathetic autonomic nucleus) accompany the oculomotor nerve and synapse in the ciliary ganglion. Then, the postganglionic fibers of the ciliary ganglion pass the short ciliary nerves to supply the sphincter pupillae muscle and the ciliary muscle, which allows the lens to thicken27 (Figure 1). This mechanism is controlled by the autonomic nervous system.23