GNK485

The eye

and

related structures

Prof MC Bosman © 2012

• Surface anatomy

• Bony orbit

• Eyeball and Lacrimal apparatus

• Extra-ocular muscles

• Movements of the eye

• Innervation

• Arterial supply and venous drainage

• Visual- and reflex pathways

• Clinical applications

Sclera

Cornea

Palpebral fissure

Sclerocorneal juncture

Pupil

Iris

Superior eyelid

Inferior eyelid

Eyelashes

Conjunctiva – bulbar and scleral

Conjunctival sac

Medial angle of the eye: lacrimal lake, lacrimal caruncle,

semilunar conjunctival fold

lacrimal punctum, lacrimal papilla

Surface anatomy

Bony orbit

•Orbit

- Cone-shaped

- Roof

- Floor

- Medial wall

lamina papyracea

- Lateral wall

- Apertures

optic canal

orbital fissures

superior

inferior

nasolacrimal canal

Bony orbit

•Orbit

- Cone-shaped

- Roof

- Floor

- Medial wall

lamina papyracea

- Lateral wall

- Apertures

optic canal

orbital fissures

superior

inferior

nasolacrimal canal

Eyeball

Eyeball

Eyeball

Eyeball - layers Outer: Fibrous [white of eye]

Sclera – opaque [posterior 5/6]

Cornea – transparent [anterior 1/6]

Middle: Vascular [uvea]

Choroid – dark, reddish brown,

blood vessels located near sclera, capillaries innermost

Ciliary body – folds are ciliary processes – secrete aqueous humor

suspensory ligaments to lens

Iris – pupil

sphincter and dilator pupillae [autonomic control]

Inner layer Retina - optic part: neural layer, pigmented layer

non-visual part: covers ciliary body and iris

Fundus – posterior part with optic disc, macula lutea with fovea centralis

Ora serrata – optic part terminates

• Eyelids

• Conjunctiva

• Peri-orbital fat

• Fibrous attachments

Eyelids

Eyelids

• Orbital septum

• Palpebral ligaments

Lacrimal apparatus

Extra-ocular muscles

• Rectus muscles

- Superior

- Inferior

- Medial

- Lateral

• Superior oblique

• Inferior oblique

• (Levator palpebrae superioris)

Movements of the eye

Abduction Lateral rectus

Adduction Medial rectus

Depression

Adduction, Extorsion

Inferior rectus

Elevation

Adduction, Intorsion

Superior rectus

Elevation

Extorsion, Abduction

Inferior oblique

Depression

Intorsion, Abduction

Superior oblique

Elevation of upper eyelid Levator palpebrae superioris

Movements of the eye

Innervation

• III

• IV

• VI

•V1

Lacrimal glands

Eyelids

• VII (Greater petrosal n)

Lacrimal glands

• Autonomic

Sympathetic

Deep petrosal n via

plexus on ICA

Parasympathetic

Short ciliary nn from

ciliary ganglion (III)

• (LR6SO4)3

Arterial supply

•Arterial supply from

the ophthalmic branch

of the internal carotid

artery

•Facial artery joins the

dorsal nasal branch of

the ophthalmic artery

•Maxillary artery –

infra-orbital artery

Venous Drainage

•Venous drainage via

superior and inferior

ophthalmic veins

•Pterygoid venous plexus

•Facial vein and danger

area

•Cavernous sinus

Visual pathway

Optic radiations

(Meyer’s loop)

Visual association

cortex, areas 18 & 19

involve posterior

temporal lobe (Wernicke)

Reflex pathway

Ciliary muscle

Red nucleus

Edinger-Westphal nucleus

Pretectal area

Short ciliary nerves

(postganglionic fibres)

Ciliary ganglion

Optic tract

Lateral geniculate body

Brachium of superior

colliculus

Constrictor pupillae

Pulvinar of thalamus

Superior colliculus

Posterior commissure

Medial geniculate body

Substantia nigra

Optic nerve

CN III (preganglionic fibres)

Reflex pathway

Corneal reflex

Any stimulus to the conjunctiva or cornea

excites blinking. Afferent fibres travel via

the ophthalmic division of the trigeminal nerve

and synapse in the spinal tract and nucleus

of CN V. Efferent impulses in branches of the

facial nerve to orbicularis oculi.

Patient not blinking:

Either V1 or VII

Test V1 on forehead to exclude

Accommodation reflex

Pathways from visual cortex

Pretectal area

Fibres from III, IV and VI cause:

(i) Vergence of the extra-ocular muscles via frontal eye fields (squint)

(ii) Parasympathetic activation of the constrictor and ciliary muscles within each eye

Clinical applications

Trochlear nerve (IV)

The patient is attempting to look down and to the

left, but his movement is impaired in the right eye.

The patient present with diplopia, especially when

reading, and difficulty in walking downstairs.

Oculomotor nerve (III)

Dense ptosis due to CN III lesion - eye rests in ‘down and out’ position

Parasympathetic component – ciliary ganglion – dilated pupil with lack of

constriction – sphincter pupillae = loss of normal pupillary reflex

Loss of accommodation – ciliary muscle

Abducent nerve (VI)

Strabismus en diplopia

Weakness or paralysis of ipsilateral lateral rectus – cannot abduct

past midline (LMN lesion)

Several mechanisms: vascular (aneurysms, infarct in pons)

4th ventricle (will also affect CN VII), infection (esp. in otitis

media), skull-base fractures, cavernous sinus pathology

Sympathetic supply

Horner’s syndrome:

(oculosympathetic

paresis)

Ipsilateral injury to

cervical sympathetic

trunk / T1 – C8

•Ptosis (partial)

•Miosis (parasymp)

•Facial anhidrosis

Facial nerve palsy

Paralysis of orbicularis oculi – closure of eyelids

Ectropion – turning outward of eyelid margin

Movement of eye unaffected

Lacrimation affected – dry eye

• Old age

• Spasm of orbicularis oculi

Entropion

Blood in the anterior chamber of the eye

http://www.eyeatlas.com

Hyphema

Position:

• In ethmoid or sphenoid sinuses erodes orbital walls

• Compression of CN II

• Proptosis

Tumour metasteses

Middle cranial fossa superior orbital fissure

Temporal / Infratemporal fossa inferior orbital fissure

Tumours

Foreign object

Retinal detachment

Trauma

http://www.oftalmo.com

Displacement of orbital wall

Unstable muscle attachments

Medial wall: -Ethmoid

-Sphenoid

Floor: Maxillary sinus

Proptosis: intra-ocular bleeding

Restricted left upgaze caused by orbital floor fracture.

http://www.eyecasualty.co.uk

Trauma ‘Blowout’ fracture

Raccoon eyes Peri-orbital bruising, # frontal skull area,

cavernous sinus thrombosis

Trauma