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Head and Neck > The Eyes > Flashcards

The Eyes Flashcards

1
Q

Which walls of the orbit are weakest and why

A

Inferior wall - formed by maxilla. Presence of maxillary sinus means the inferior wall is thin

Medial wall - formed by ethmoid bone. Is very thin as it has air cells within the bone

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2
Q

Name some of the openings in the orbtial apex and what structures enter into and out of the orbit

A

Optic canal - optic nerve and ophthalmic artery

Superior orbital fissure - CN III, IV, VI, Va, superior ophthalmic vein

Inferior orbital fissure - infraorbital nerve (branch of CN Vb), inferior ophthalmic vein

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3
Q

What is the blood supply to the orbit and eye

A

Main artery supply is ophthalmic artery - central retinal artery pierces dura surrounding optic nerve to enter with it into the eye

Ophthalmic veins drain venos blood into cavernous sinus, pterygoid plexus, facial vein

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4
Q

What is the nervous innervation to the eyes

A

General sensory - CN Va

Special sensory - CN II

Motor function - CN III, IV and VI

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5
Q

What are the layers of the eye

A

Sclera - outer

Choroid/Middle

Retina - inner

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6
Q

How is the eyeball position maintained

A

Suspensory ligament

Exra-ocular muscles

Orbital fat

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7
Q

Describe the sclera

A

Outer protective layer

Is tough and fibrous

Provides attachment for extraocular muscles, gives shape to eyeball and is continuous with dural sheath covering optic nerve

Is covered by the conjunctiva

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8
Q

Describe the conjunctiva

A

Thin transparent layer of cells that covers the eyeball, except for the cornea

Covers the sclera and lines inside of eyelids forming conjunctival sacs

Blood vessels run through the conjunctiva to supply blood to sclera

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9
Q

Describe the middle layer of the eyeball

A

RIch, vascular area of the eyeball

Includes choroid, ciliary process and iris - the uvea

Ciliary body connects choroid with the iris and consits of ciliary process and muscle

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10
Q

Describe the retina

A

Inner layer of the eye and consists of photosensitive and non-photosensitive parts (pigmented layer)

Pigmented layer lies between choroid and neurosensory layer of retina. Cells contain melanin which help absorb scattered light that has passed into the eye to focus light onto the retina (macula)

Neurosensory layer senses light and is where photoreceptors (rods and cones) are found

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11
Q

Describe the differences between rods and cones

A

Cones are responsible ofr high visual activity and colour vision. Are concentrated in the macula - fovea is found in centre of macula where only cones are found

Rods - responsible for vision in low intensity light and do not discern colours. Most abdunant towards peripheral parts of retina

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12
Q

What are the chambers of the eye and what is found in each

A

Vitreou chamber - vitreous humour found within

Anterior chamber - aqueous humour

Posterior chamber - aqueous humour

Aqueous humour important in supporting shape of eye and in nourishing lens and cornea

Aqueous humour drains through irido-corneal angle into canal of Schlemm via trabecular network

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13
Q

Describe the iris

A

Thin contractile diaphragm with a central appeture, the pupil, for transmission of light

Gives eye colour

Sphincter and dilator pupillae form iris and control size of pupil

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14
Q

Describe the lens

A

Transpartent biconvex structure enclosed in a capsule

Recieves nutrients from aqueous humour

Edges attach to ciliary body by circular suspensory ligament

Contraction of ciliary muscle alters tension in suspensory ligament allowing for changes in shape of the lens and its refractive power

Becomes fatter to allow focusing of near-objects

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15
Q

How do cataracts develop

A

Proteins degrade as we age causing the lens to become cloudy and less transparent resulting in cataracts

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16
Q

What structures help refract light towards the macula

A

Cornea and tear film - main refractor but cannot cope with near-objects

Lens

Aqueous humour and vitreous humour

17
Q

Describe the accomodation reflex

A

Pupillary constriction occurs to ensure light from near-object passes through centre of the lens

Eye convergence ensures both retina focus on one object

Contraction of ciliary muslce causes lens to beocme more biconvex by loosening circular suspensory ligaments

Lens becomes more biconvex to allow for better focusing of near-objects on the retina

18
Q

Why do patients develop presbyopia

A

Because as patients age, lens becomes more dense, less elastic and more difficult to change shape

This means ability to accommodate and focus on near-objects is impaired

19
Q

What does the eyelid consist of and what glands are found in it

A

Eyelid consists of skin, subcutaneous tissue, tarsal plate and muscle

Meibomian gland - secretes oily substance onto edges of lid to help prevent evaporation of tear film and tear spillage. Bocked = meibomian cyst

Sebaceous glands - assocaited with lash follicle. Can be blocked causing Syles - painful, white head and red eyelid

20
Q

What is the orbital septum and what is its function

A

Orbital septum is a thin sheet of fibrous tissue originating from orbital rim that blends with tarsal plates

Orbital septum and tarsal plates separate subcutaneous tissue of eyelid and orbicularis oculi from intra-orbital contents

21
Q

Describe the lacrimal apparatus

A

Consists of lacrimal gland, ducts and canaliculi

Glands secrete lacrimal fluid -> enters conjunctival sac through lacrimal ducts -> passes into lacrimal lake

Fluids drains into canaliculi -> lacrimal sac -> passes into nasal cavity via nasolacrimal duct

Obstruction of drainage system causes epiphora

22
Q

What muscles move the eyelid, what are their movement and what are they innervated by

A

Orbicularis oculi - closes eyelid. Innervated by facial nerve

Levator palpebrae superioris - opens eyelid. Innervated by oculomotor nerve

Superior tarsal muscle - sympathetic nervous system

23
Q

What muscles are responsible for eyemovements and what are they innervated by

A

Extra-ocular muscles

Superior, inferior, medial and lateral rectus

Superior and inferior oblique

Oculomotor innervates superior, inferior and medial rectus and inferior oblique

Lateral rectus - abducens nerve

Superior oblique - trochlear nerve

24
Q

Where do the extraocular muscles arise

A

Recti muscles originate from common tendinous ring

Oblique muscles originate from bony walls of orbit

25
Q

What are the actions of the recti muscles

A

Medial rectus - adducts eye

Lateral rectus - abducts eye

Superior rectus - elevates, slightly intorts, slightly adducts eye

Inferior rectus - depresses, slightly extorts, slightly adducts eye

26
Q

What are the actions of the oblique muscles

A

Superior oblique - intorts, depresses, slightly abducts eye

Inferior oblique - extorts, elevates, slightly abducts eye

27
Q

Describe how muscles are tested during the clinical examination of extraocular muscles

A

When eyes abducted:

  • Elevation = superior rectus
  • Depression = inferior rectus

When eyes adducted:

  • Elevation = inferior oblique
  • Depression = superior oblique
28
Q

Describe the steps in the clinical examination of the eye

A

IVA FORM

I - inspection

VA - visual acuity - snellen chart

F - visual fields

R - reflexes

O - opthalmoscope

M - eye movements

Head and Neck (22 decks)

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