Lecture 7 - Orbit, Eyelids, and Lacrimal Apparatus PDF

The Orbit ± The orbits are two bony cavities shaped like a pyramid with the apex directed posteriorly and the base anteriorly. ± They are formed by the following bones: ± Frontal ± Greater and lesser wings of the sphenoid ± Zygomatic ± Ethmoid ± Maxilla ± Lacrimal ± BOUNDARIES: ° Supraorbital margi...

The Orbit ± The orbits are two bony cavities shaped like a pyramid with the apex directed posteriorly and the base anteriorly. ± They are formed by the following bones: ± Frontal ± Greater and lesser wings of the sphenoid ± Zygomatic ± Ethmoid ± Maxilla ± Lacrimal ± BOUNDARIES: ° Supraorbital margin ± Supraorbital notch ± Frontal notch ° Lateral margin ± Orbital tubercle ± Lateral palpebral ligament ° Infraorbital margin ° Medial margin ± Anterior lacrimal crest ± Fossa of the lacrimal sac ° Posteriorly ± Superior orbital fissure ± Inferior orbital fissure ± Optic canal THE ORBIT Clinical Considerations ±Orbital Fractures °Because of the thinness of the medial and inferior walls of the orbit, a blow to the eye may result in orbital fractures. °Indirect trauma that displaces the orbital walls is called a “blowout” fracture. °Fractures of the medial wall may affect the sphenoidal and ethmoidal sinuses, whereas fractures of the inferior wall may affect the maxillary sinus. A 76-year-old man fell from a six-foot ladder, incurring trauma to the right side of the face. He complained of paresthesias of the infraorbital nerve distribution with right maxillary ecchymosis and pain Clinical Considerations ±The superior orbital wall is stronger than the medial and inferior walls, but it is thin enough to sustain injury. ±Therefore, a sharp object may penetrate the wall and enter the frontal lobe of the brain. Clinical Considerations ±Orbital fractures often result in intra-orbital bleeding, which may increase the pressure and push on the eyeball causing a condition known as exophthalmus. Clinical Considerations ±Any trauma to the eye may also affect adjacent structures: °Bleeding into the maxillary sinus °Displacement of maxillary teeth °Fracture of nasal bones causing hemorrhage, airway obstruction, and infection that could spread to the cavernous sinus via the ophthalmic vein. Clinical Considerations ±Periorbital Ecchymosis °Direct trauma (blows) to the periorbital region often causes swelling and hemorrhage into the eyelids and extravasation of blood into the periorbital skin (ecchymosis). °These types of injuries are common in contact sports and boxing. This 17-year-old man presented with a three-day history of double vision on upward gaze after having been struck in the right eye with a clenched fist. The periorbital ecchymosis, edema, subconjunctival hemorrhage, and paresis on upward gaze are suggestive of a particular injury. ORBITAL FLOOR FRACTURE WITH ORBITAL STRUCTURE ENTRAPMENT. NOTE THE BLOOD IN THE MAXILLARY SINUS AND EXTRUSION OF ORBITAL CONTENTS THROUGH THE DEFECT THE EYELIDS The Eyelids ±The eyelids cover the eyeball anteriorly (when closed), thereby protecting it from injury and excessive light. ±They also protect the cornea by keeping it moist and spreading the lacrimal fluid over it. ±The place where the eyelids meet is the angle (canthus) of the eye - medial and lateral canthi. These measurements indicate the width of the normal palpebral fissure. It is important to know these measurements because there are a number of diseases in which they are altered. For example, the palpebral fissure may be widened in peripheral facial muscle paralysis or narrowed in ptosis due to oculomotor nerve palsy. 3 mm 2 mm 9 mm (6-10) 28-30 mm Width of the Palpebral Fissure The Eyelids ±The eyelids are moveable folds covered by thin skin externally and internally by palpebral conjunctiva. ±The palpebral conjunctiva is reflected onto the eyeball, where it becomes continuous with the bulbar conjunctiva. ±The bulbar conjunctiva covers the sclera, and it is adherent to the periphery of the cornea. ±The bulbar conjunctiva contains small apparent blood vessels. * * Superior tarsal muscle This muscle is under the control of the SNS The Eyelids ±The superior and inferior eyelids maintain their shape and rigidity due to the presence of a tarsal plate in each eyelid. ±The tarsal plates form the “skeleton” of the eyelids. ±The tarsal plates are suspended in the eyelids by the orbital septum (connective tissue membrane that spans from the tarsal plates to the margins of the orbit where it is continuous with the periosteum). The Eyelids - Glands of the Eyelids ±Meibomian (Tarsal) Glands °These glands are embedded in the tarsal plates. °They produce and oily secretion which lubricates the edges of the eyelids and prevents them from sticking together when the eyelids are closed. °This lipid secretion also forms a barrier to prevent the overflow of tears (i.e., at the lid margins, the oily layer prevents normal amounts of tears from flowing out of the eye). The Eyelids - Glands of the Eyelids ±Ciliary (of Zeis) Glands °These are large sebaceous glands associated with the eyelashes. °They secrete sebum into the eyelash hair follicles thus preventing the eyelash from becoming brittle. The Eyelids - Glands of the Eyelids ±Glands of Moll °Modified sweat glands near the lid margins, may empty several places including same route as glands of Zeis. °Their function is unknown. The Eyelids - Ligaments of the lids ±Between the nose and the medial canthus of the eye is the medial palpebral ligament, which connects the tarsal plates to the medial margin of the orbit. ±The orbicularis oculi muscle originates and inserts onto the ligament. The Eyelids - Ligaments of the lids ±A similar lateral palpebral ligament attaches the tarsal plates to the lateral margin of the orbit but does not provide for muscle attachment. The Eyelids - Muscles ± Levator Palpebrae Superioris ° Elevates the eyelid ° Inserts into the superior tarsal plate with the orbicularis oculi ° Supplied by CN III ± Superior Tarsal Muscle (Mueller’s muscle) ° Involuntary, smooth muscle innervated by sympathetic fibers ° Assists in elevation of the eyelid and inserts in the superior tarsal plate ±Inferior Tarsal Muscle °Thought to depress the inferior eyelid, and widen the palpebral fissure °Supplied by SNS ±Orbicularis Oculi Muscle °Closes the eyelids °Supplied CN VII The Eyelids - Nerves ±Sensory °CN V1 (ophthalmic division) to upper lid °CN V2 (maxillary division) to lower lid ±Motor °CN VII to Orbicularis Oculi muscle °CN III to Levator Palpebrae Superioris muscle °Sympathetic postganglionic fibers from the superior cervical ganglion to Superior and Inferior Tarsal muscles Clinical Considerations ±Inflammation of the Palpebral Glands °Any of the glands of the eyelids can become inflamed due to infection or obstruction of their ducts. °If the ducts of the ciliary glands (of Zeis) become obstructed, a painful, suppurative swelling - a stye (hordeolum) - develops on the eyelids. °Staph bacteria is usually the cause. Clinical Considerations ±Obstruction of the tarsal meibomian lead to cyst formation referred to as chalazion a glands, producing a non-painful inflammation that may protrude toward the eyeball and rub against the cornea. Clinical Considerations ±Hyperemia of the Conjunctiva °The bulbar conjunctiva is colorless except when its blood vessels become congested and dilated “bloodshot eyes”. °Hyperemia of the conjunctiva may be caused by local irritation (e.g., from dust, smoke, chlorine). °Conjunctivitis -”pinkeye” - is a common, contagious infection of the eye. °Viral (adenoviruses) – very contagious. Can lead to outbreaks °Bacterial (strep, staph, H. influenza, chlamydia, Neisseria, etc.) Clinical Considerations ±Subconjunctival Hemorrhages °Common °Manifested by bright or dark red patches deep to and in the bulbar conjunctiva. °These hemorrhages may result from injury or inflammation. °A direct blow to the eye, excessive hard blowing of the nose, and paroxysms of coughing or violent sneezing may cause hemorrhages resulting from rupture of the small subconjunctival capillaries. Clinical Considerations ±Injury to the nerves supplying the eyelids °A lesion of the oculomotor nerve (CN III) will cause paralysis of the levator palpebrae superioris muscle causing ptosis (drooping) of the upper eyelid. °Loss of sympathetic supply to the eye may result in paralysis of the superior tarsal muscle leading to partial ptosis. °Damage to the facial nerve (CN VII) will cause paralysis of the orbicularis oculi muscle resulting in inability to close the eyelids. The normal rapid blinking protective reflex is also lost. Clinical Considerations °The loss of muscle tone in the lower eyelid causes the lid to sag (become everted) away from the surface of the eye. This leads to drying of the cornea resulting in irritation which leads to excessive but insufficient lacrimation. The unprotected cornea is susceptible to damage from foreign particles which could result in scratches and ulcerations. Injury of the Nerves of the Eyelid-Summary ±Injury to CN III causes inability to voluntarily open the upper eyelid. ±Injury to the sympathetic postganglionic fibers from the superior cervical ganglion will result in constant partial ptosis. ±Loss of innervation to the orbicularis oculi by CN VII causes an inability to voluntarily close the eyelids tightly and the lower eyelid droops away (ectropy), resulting in spillage of tears (epiphora). SYMPATHETIC NERVE INJURY TO THE EYE (e.g., Horner’s Syndrome) partial-ptosis CN III INJURY - Full-ptosis The Lacrimal Apparatus ±The lacrimal gland is located at the superolateral quadrant of the orbit. ±The lacrimal sac is located at the medial margin of the orbit. The lacrimal sac is connected to the nasolacrimal duct. ±Secretory fibers to the lacrimal glands are from the greater petrosal nerve (CN VII) and the nerve of the pterygoid canal. ±The nasolacrimal duct drains into the inferior nasal meatus. Clinical Considerations ±Excessive lacrimation may result from obstruction of the lacrimal duct. ±People often dab their eyes constantly to wipe the tears, resulting in further irritation.