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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