Session 9

Question 1

Borders of the orbit?

Answer 1

Roof- Frontal bone

Floor- Maxilla (maxillary sinus)

Lateral- Zygomatic

Medial- Lacrimal, Ethmoid (ethmoidal air cells)

Question 2

Blood supply to orbit?

Drainage?

What supplies general sensory to eye? (Conjunctiva/cornea)

Special sensory (retina)?

Motor nerves to muscles?

Answer 2

Ophthalmic artery

Sup/inf ophthalmic veins drain into cavernous sinus

Trigeminal (Va)

Optic nerve

3,4,6

Question 3

What spreads infection to eye?

Weakest point and why?

What causes the fracture?

Answer 3

Nasolacrimal duct

Medial and floor wall of orbit as thin and air spaces behind

Sudden increase in intra-orbital pressure.

Question 4

Presentation of orbital blow out fractures?

Answer 4

Prevention in upward gaze on affected side-as orbital contents can prolapse and bleed into maxillary sinus so extra ocular muscle can become trapped at fracture site.
Periorbital swelling/pain
Double vision on vertical gaze
Numbness over cheek-infraorbital nerve (branch of maxillary) runs along floor of orbit.

Question 5

Role of orbicularis oculi?

Levator palpebrae superioris?

Role are where found of Meiobian glands? If blocked?

What causes styes?

Answer 5

Lifts eyelid up

Pulls eyelid down

In tarsal plate, secretes oily part of tear fluid. Meiobian cyst.

Eyelash follicle or associated sebaceous gland blockage or infection.

Question 6

What is blepharitis?

What’s the orbital septum?

Answer 6

Inflammation of eyelids including Meibomian glands.

Thin sheet of fibrous tissue from orbital rim blending with tarsal plates. Together separating subcutaneous tissue and muscle from intra-orbital contents. Stopping infection spreading into post-septal space.

Question 7

Where does the infection occur in periorbital (pre septal) cellulitis?

Orbital (post-septal) cellulitis?

Complication?

Answer 7

Infection in eyelid tissue. Secondary to superficial infection from bites or bacterial sinusitis (ethmoidal). Ocular function unharmed.

In the orbit,posterior to septum. Site threatening. Eyeball pushed forward (proptosis),pain,reduced visual acuity.

Infection can spread via ophthalmic vein into carvernous sinus causing a thrombosis or meningitis as infection now intracranial.

Question 8

What produces years and how transported?

Role of blinking?

What can obstruction of the tear drainage system lead to?

Answer 8

Lacrimal duct transported by lacrimal sac and duct. Drained into nasal cavity.

Distributes year film across eye lubricating conjunctiva and cornea.

Epiphora-overflow of tears over lower eyelid

Question 9

3 layers to eyeball?

What maintains the eyeballs position?

Answer 9

Fibrous tunic (outer) transparent sclera and cornea.
Vascular tunic, choroid,iris,ciliary body.
Retina (pigmented and neural photosensitive layer)

Suspensory ligaments,extra ocular muscles, orbital fat.

Question 10

What is the conjunctiva? What does it cover?

Limbus?

Feature of conjunctiva?

Complication?

Answer 10

Transparent mucous membrane, covering ant surface of eyeball. Producing mucous component of tear film.

Junction of conjunctiva with cornea which has its own epithelial lining.

Highly vascular

Subconjunctival haemorrage

Question 11

What structures refract light onto back of retina?

Myopia?

Hypermetropia?

Answer 11

Cornea,Lens,aq humour

Short sited

Long sited

Question 12

Focusing of near objects requires? Why can’t the cornea help?

How does the eye accommodate a nearer object?

Presbyopia?

Answer 12

Greater refraction of light. Cornea is fixed in shape.

Pupil constricts (limiting light)
Eyes converge so image focused on same point of retina on both eyes.
Lense more biconcave (fat) by contraction of ciliary.

Age related inability to focus on near objects as lense is stiffer.

Question 13

Role of Rods? When Abundant?

Cones?

Where do retinal ganglion cells collect to form the optic nerve and significance?

Answer 13

Black and white at low levels of light abundant in peripheral parts of retina.

High definition colour vision in high levels of light. Abundant in macula of retina. Especially fovea.

Optic disc, blind spot as no photoreceptors.

Question 14

Cataracts?

Astigmatism?

Presbyopia?

What do these and retinal detachment have in common?

Answer 14

Opacity of lens

Irregularity of corneal surface prevents proper refraction

Inability of lens to change shape

All cause blurry vision

Question 15

What is the macula?

If blurring of vision improves with pin hole?

If doesn’t improve then what?

Answer 15

The point where light is focused on the retina

Refractive error as no refraction if light is travelling perpendicular.

Either retinal or optic nerve issue

Question 16

What helps maintain the shape of the eyeball?

What secretes humour?

It’s other role?

How it drains?

Answer 16

The anterior and posterior chambers full with aq humour

Ciliary processes in ciliary body

Nourishes lens and cornea

Through iridocorneal angle via trabecular mesh into canal of schlem (draining into venous system)

Question 17

What is glaucoma?

Two types?

Answer 17

Optic nerve damage due to raised intraocular pressure, caused by blockage of humour drainage from anterior chamber.

Chronic-open angle glaucoma-trabecular mesh deteriorates with age,increased IOP causing increased optic disc cupping so gradual loss of peripheral vision.

Acute-closed angle glaucoma-narrowing of iridocorneal angle, the lens pushes forward and it’s an emergency.

Question 18

Cupping?

Symptoms of acute glaucoma?

Answer 18

Optic nerve/disc ratio increases

Red painful eye, halo around lights due to corneal oedema, oval shaped pupil, blurring of vision.

Question 19

What eye muscles are under autonomic control?

6 key extra ocular muscles?

Origin of them all?

What must be for resting gaze? If maligned then?

Answer 19

Ciliary muscles controlling thickness of lens and muscles of iris (dilator and constrictor muscles of pupil).

Sup,inf,med,lat rectus muscles and sup,inf oblique

Common tendinous ring from the apex of the orbit

Their actions are balanced and visual axes of both eyes are aligned. If maligned then diplopia.

Question 20

Action nerve of medial rectus?

Action nerve of lateral rectus?

Action nerve of superior rectus?

Action nerve of inferior rectus?

Answer 20

Adduction, occulomotor nerve

Abduction, Abducens nerve

Elevates the eyeball,slight adduction and intortion, sup div of oculomotor.

Depresses eyeball,slight abduction, extortion, inf div of oculomotor

Question 21

Trochlear?

Nerve action of Sup oblique?

Inferior oblique?

Answer 21

Superior oblique muscle passes through it

Intorts the eyeball and depresses.slightly abducts. Trochlear nerve.

Extorts,elevates,adducts inf branch of oculomotor

Question 22

How do you differentiate sup/inf obliques in eye test?

For rectus?

What can affect cranial nerves?

Answer 22

Start medially then test elevation and depression

Start laterally then test

IntracraniL haemorrage,tumour,diabetes,hypertension

Question 23

Other than extra ocular muscles what does the oculomotor nerve innervate?

What does trochlear innervate? If damaged? When diplopia worse?

Abducens palsy?

Answer 23

LPS (eyelid) and sphincter pupillae

Superior oblique only. If damaged extorted,elevated,adducted. Looking down and medially.

Does lateral rectus so If damaged then unopposed pull of medial rectus and inability to abduct the eye.