WINDSOR UNIVERSITY SCHOOL OF MEDICINE DEPARTMENT OF ANATOMY Head and Neck Dr. SREEKANTH THOTA

Gross Anatomy Eye

ORBIT The orbits are bilateral structures in the upper half of the face below the anterior cranial fossa and anterior to the middle cranial fossa that contain the eyeball, the optic nerve, the extraocular muscles, the lacrimal apparatus, adipose tissue, fascia, and the nerves and vessels that supply these structures.

Bony orbit Seven bones contribute to the framework of each orbit 1. Roof 2. Medial wall 3. Floor 4. Lateral wall

Openings Into the Orbital Cavity 1. Supraorbital notch (Foramen) 2. Nasolacrimal canal 3. Superior orbital fissure 4. Optic canal 5. Infraorbital groove and canal

Eyelids The layers of the eyelids, from anterior to posterior, consist of 1.Skin, subcutaneous tissue 2. Voluntary muscle 3.orbital septum 4.Tarsus 5. Conjunctiva

Muscles of the Eyelid 1.Orbicularis oculi: Closes the eyelid…. Important in blinking. Facial nerve palsy results in inability to close the eye & can cause excessive dryness & irritation of the eye. [patient may sleep with eyes partially open!] 2. Muscles for elevating upper eyelid 1. levator palpebrae superioris 2. Superior tarsal (Muller’s muscle)

Orbicularis oculi

Ptosis: Can result due to oculomotor nerve palsy (levator palpebrae superioris) OR Due to Damage to sympathetic nerves supplying Muller’s muscle. (Horner’s syndrome)

The eye lid

Chalazion: A chalazion , is a cyst in the eyelid that is caused by inflammation of a blocked meibomian gland or tarsal gland usually on the upper eyelid.

Chalazion

Stye An external stye is an infection of the sebaceous glands of Zeis at the base of the eyelashes, or an infection of the apocrine sweat glands of Moll.

Extra occular muscles

NERVE SUPPLY OF EXTRAOCULAR MUSCLES (LR6SO4)3

Muscles of the orbit Muscle Action on the Eyeball Nerve supply Medial rectus Adducts (pupil moves medially) CN III Lateral rectus Abducts (moving the pupil laterally) CN VI Superior rectus Elevates, adducts

Muscles of the orbit Inferior Rectus Depresses, adducts CN III Superior Oblique Depresses, abducts CN IV Inferior Oblique Elevates, abducts

Movements of the eyeball

ACTION OF INDIVIDUAL MUSCLES ON THE EYEBALL

BLOOD VESSELS OF THE ORBIT Ophthalmic Artery Branch of the internal carotid artery Passes through the optic canal Branches: 1.central artery of the retina – 2.ciliary arteries – 3.lacrimal artery – to the lacrimal gland 4.supratrochlear 5.supraorbital arteries – skin of forehead 6. Anterior and posterior ethmoidal artery

Ophthalmic Veins 1. Superior ophthalmic vein – communicates anteriorly with the facial vein. 2.Inferior ophthalmic vein – communicates through the inferior orbital fissure with the pterygoid plexus of veins 3.both veins drain into the cavernous sinus

Ophthalmic Nerve (CN V1) a. Lacrimal nerve passes to the lacrimal gland providing secretomotor fibers b. Frontal nerve Divides into supratrochlear and supraorbital nerves C. Nasociliary nerve: Anterior and posterior ethmoidal nerve

Oculomotor nerve Just before entering the orbit the oculomotor nerve [III] divides into superior and inferior branches.

Lacrimal apparatus Production, movement and drainage of fluid from the surface of the eyeball Composed of -Lacrimal glands and its ducts -Lacrimal canaliculi -Lacrimal sac -Nasolacrimal duct

Tears(Lacrimation) Parasympathetic innervation Greater petrosal branch of facial nerve.

Conjunctiva Bulbar conjunctiva covers exposed part of sclera Palpebral conjunctiva – covers inner surface of eyelids.

The eyeball Contains the optical apparatus of the eye Has 3 layers Outer Fibrous layer-opaque sclera and transparent anterior cornea Middle Vascular layer- Choroid -(posterior), Ciliary body and Iris (uvea)- (anterior), Inner layer (sensory)-Retina

Ciliary body composed of the ciliary processes and ciliary muscle A. Ciliary processes – folds or ridges on internal surface ciliary body  secrete aqueous humor; posterior surface encircles the lens and connected to it by the suspensory ligament of the lens. B.Ciliary muscle – consists of smooth (intrinsic) muscle; contraction releases tension in the suspensory ligament of the lens making it more convex and increasing its refractive power (for near vision); nerve supply – parasympathetic (CN III).

Production of Aqueous Humor and Intraocular pressure Ciliary Process: Produces Aqueous Humor 2. Posterior Chamber: Aqueous Humor flows from this chamber through the pupil in Anterior Chamber Canal of Schlemm Reabsorbs Aqueous Humor Glaucoma: Increase in intraocular pressure due to build up of Aqueous Humor

Iris consists of two smooth (intrinsic) muscles that control the size of the pupil Sphincter pupillae – circular arranged fibers; constricts (closes) pupil in presence of bright light; nerve supply - parasympapathetic (CN III) Dilator pupillae – radially arranged fibers; dilates (opens) pupil in presence of low intensity light or in presence of excessive sympathetic activity as occurs in fright; nerve supply – sympathetic

Lens It is an encapsulated, elastic, biconvex transparent structure. Suspensory ligament connects it to the ciliary body.

Cataracts Cataracts - clouding or opacification of the natural lens of the eye Cataract Vision

Cataract A cataract is any opacity within a lens. The opacity can be very small (incipient cataract) and not interfere with vision. It can involve more of the lens (immature cataract) and cause blurred vision. Eventually, the entire lens can become cloudy, and all functional vision lost. This is called a mature cataract.

How can cataracts be treated? The only treatment for cataracts is surgical removal. Cataract surgery is the removal of the eye lens and replacing it with an artificial one.