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Flashcards in Week 6- The eye Deck (112):

Where are the lacrimal glands located?

  • In a fossa on the superolateral part of the orbit 


What do the lacrimal glands produce?

  • Fluid that lubricates the eye
  • If lots if produced then it overflows and this is when you cry 


What is the lacrimal lake? Where does fluid drain from here?

  • The bottom part of the eye where fluid collects
  • It drains into the lacrimal sac via lacrimal canals
  • Then drains into nasolacrimal ducts and into the inferior meatus of the nasal cavity 


What is the orbit?

  • A pyrimidal shaped bony caivty in the facial skeleton.
  • It contains (and protects):
    • The eyeball 
    • Muscles 
    • Nerves 
    • Vessels 
    • Most of the lacrimal apparatus 


what are the boundaries of the orbit?

  • Apex
    • Orbital canal (site of entrance of optic nerve into orbit)
  • Superior (roof):
    • Frontal 
    • Sphenoid
  • Lateral: 
    • Zygomatic
    • Sphenoid
  • Medial:
    • Ethmoid
    • Maxillary
    • Lacrimal 
    • Sphenoid
  • Inferior 
    • Maxillary 
    • Zygomatic 


which is the weakest boundary of the orbit?

The inferior boundary 


Which bone of the orbit is the most likely to fracture?

  • the sphenoid
  • As it has lots of foramina/canals in 


Which bone contains all the holes of the orbit in? what are the exceptions?

  • Sphenoid
  • Except infra-orbital foramina which are in the maxilla and transmit the infra-orbital nerve 


What is the pneumonic to remember the nerves of the superior orbital fissure from suprior to inferior?

  • Litte (lacrimal branch of ophthalmic nerve (V1))
  • Friendly (frontal branch of ophthalmic nerve)
  • Tortoises (trochlear nerve)
  • Sit (superior division of oculomotor nerve)
  • Nicely (nasociliary branch of ophthalmic nerve)
  • In (inferior division of oculomotor nerve)
  • Anticipation (abducens nerve)


As well as cranial nerves what else runs through the superior orbital fissure?

  • Superior ophthalmic vein 


What runs through the optic canal?

  • Optic nerve 
  • Ophthalmic artery 


What runs through the inferior orbital fissure?

  • Inferior ophthalmic vein 
  • Maxillary nerve and its zygomatic branch 
  • Sympathetic nerves 


what are the 3 layers of the eyeball?

  • Outer fibrous layer 
    • Sclera and cornea 
  • Middle vascular layer
    • Choroid, iris and ciliary body 
  • Inner layer
    • retina 


what is the function of the outer fibrous layer of the eyeball? what is the sclera continuous with?

  • helps give the eye its shape 
  • It is continuous with the dural sheath covering the optic nerve as the back of the eye 


What it the iris?

  • Coloured part of the eye around the lens
  • It is a thin contractile diaphragm with a central apeture (pupil)


What is the function of the middle vascular layer of the eye?

  • has a rich network of blood vessels and supplies nutrients to the avascular areas e.g. lens and back of eye 


Where is the location of the rods and cone cells? What do they do?

  • The retina
  • They convert light signals to nerve impulses which are sent to the brain 


What are the two parts of the retina?

  • Optic and non-visual parts 


What shape is the lens? what is its function?

  • Bioconvex
  • Focuses light onto the retina 


What is the innervation and blood supply of the lens?

  • It has no innervation or blood supply and so receives its nutrients from aqueous humour that surrounds and bathes it 


How does the lens allow for long and short sighted vision?

  • Contraction of ciliary muscle fibres under parasympathetic control alters the tension in the suspensory ligaments 
  • This causes changes in the lens shape and so changes its refractive power allowing for long and short sighted vision 


what is the optic disc?

  • This is where the optic nerve enters the eye 
  • All blood vessels converge to his area (as this is where theyleave the eye)
  • It contains no rods/cones and so gives rise to the blind spot 


What is the macula/fovea?

  • The macula is a kind of circle with the fovea at its centre
  • Together this makes up the area of most accurate/acute vision 
  • Contains the most rod/cone cells which are involved in the conversion of light


Who do we look for papiledema in?

  • People who suffer migraines/headaches (it is a sign of raised intra-cranial pressure)


What is a fundus?

An image taken on a fundoscope


How can we figure out which eye we are looking at on a fundus?

  • Look for:
    • Optic disc (point of convergence of blood vessels)
    • Fovea/macula (appears as a dull spot)
  • The optic disc is always on the nasal side (closest to the nose) on the fundus 


What does the fundus appear like in someone with retinal detachment?

  • Part of the fundus becomes kind of cloudy looking and you can't see blood vessels in the affected area
  • You may also see retinal tears within the detachment (appear darker) 


Why can you get partial blindness even after surgery when you have retinal detachment?

  • If you leave the retinal detachment for too long the lack of blood supply to the retina means that it can't be fixed so even when it is reattached you still get partial blindness


Describe the layers surrounding the optic nerve

  • It is a continuation of the brain itself so has three layers of the brain around it:
    • Pia mater (inner layer)
    • Arachnoid mater
    • Dura mater (outer layer)


Why do we get photophobia when there is inflammation in the brain?

  • Because this also causes inflammation of the dura and because this  surrounds the optic nerve this causes compression of the nerve 
  • The caues pain especially when you look at light (photophobia)


What are the segments of the eye?

  • Anterior segment
    • Anterior chamber 
    • Posterior chamber
  • Posterior segment 
    • vitreous body (contains vitreous fluid which helps keep the shape of the eye)


Where is the anterior chamber of the anterior segment of the eye? How does it communicate with the posterior chamber?

  • it is between the iris and the cornea's innermost surface (endothelium)
  • It communicates with the posterior chamber through the pupil 


Where is the posterior chamber of the anterior segment of the eye?

  • Posterior to the iris but anterior to the lens 


what does the posterior chamber of the anterior segment of the eye?

  • Ciliary body and ciliary processes
  • These produce aqueous fluid which moves up round the lens and iris into the anterior chamber and helps supply nutrients to the avascular lens and cornea and helps maintain the shape of the eye 


Describe the drainage of the aqueous humour from the posterior chamber of the anterior segment of the eye

  • Drains into the irido-corneal angle 
    • This is the space between the anterior surface of the iris and posterior extremity of cornea
  • Drains from there into the canal of Schlemm via the tabecular meshwork into the venous circulation


What can occur as we get older that can lead to glaucoma? If untreated what can this cause?

  • a blockage of aqueous humour can occur as we get older causing an increase in intra-ocular presure so leading to glaucoma 
  • If untreated the increase in pressure can cause irreversible damage/death of the optic nerve causing impairment of vision or blindness 


What is the most common type of glaucoma?

Open-angle glaucoma 


Describe how open-angle glaucoma occurs

  • blockage within trabecular meshwork causes iris to be pushed away from cornea and the angle between them to increase (become more open)
  • It develops painlessly over time and can be difficult to pick up 


When is open-angle glaucoma screened for? What are other signs of it  as well as increased intra-ocular pressure?

  • By opticians in routine eye tests 
  • Intra-ocular pressure can be measured by a brief puff of air against the cornea 
  • Signs:
    • Cupping of the optic disc
    • Visual field loss 


Describe the treatment of open-angle glaucoma

  • Topical medications (eye drops) that recuce aqueous humour production (e.g. Beta-blockers, timolol) and/or increase its drainage
  • If these fail then surgery (trabeculectomy) may be needed 


Describe how closed-angle glaucoma occurs

  • Irido-corneal angle is narrowed by peripheral edge of the iris 
  • Access to the trabecular meshwork is blocked off leading to a rapid rise in intra-ocular pressure 
  • Acute presentation is a ophthalmological emergency and requires rapid management as irreversible sight loss can occur within a few hours 


Who is most as risk of closed-angle glaucoma?

  • Long-sighted middle aged or elderly people (with shallow anterior chambers) are most at risk


What does closed-angle glaucoma acutely present with?

  • Sudden onset of red painful eye 
  • Blurred vision or halos around objects (due to corneal oedema)
  • Fixed or sluggish semi-dilated often irregular, oval-shaped pupil 
  • Nausea and vomiting
  • Eye feels hard and tender to palpare through the upper eyelid 


What is the management of closed angle-glaucoma?

  • Muscarinic eye drops e.g. pilocarpine 
  • Strong analgaesia and drugs to reduce intra-ocular pressure while awaiting an emergency ophthamology opinion 


what happens to the lens as we age? What can this lead to?

  • Degradation of the proteins in the lens occurs and it becomes cloudy and less transparent causing cataracts 
  • Cataracts occur gradually 


How are cataracts treated?

  • Simple non-invasive operation under anaesthetic in which the existing lens is removed and a new one put in 
  • This improves the patient's sight and quality of life


What is the accomodation reflex?

  • Autonomic contraction of pupils and convergence of the eyes that occurs when focusing on a near object, immediately after focusing on a distant object 


How is the accomodation reflex tested?

  • In a full cranial nerve examination 
  • With direct and consensual pupillary light reflexes 


Why does contraction of the pupil and convergence of the eyes occur during the accomodation reflex?

  • Contraction of the pupils 
    • so that light from the near object passes through the centre of the lens 
  • Convergence of the eyes
    • Ensures the retina are focusing on one object


What else occurs during the accomdation reflex which is not visible to the examiner?

  • Change in shape of the lens due to contraction of the ciliary muscle
    • This contraction 'loosens' the pull of the circular suspensory ligaments on the lens so allows it to become more bioconcave (round)


Why do people have to hold things with small writing e.g. menus at arms-length to focus as they get older?

  • As we age the lens becomes dense, less elastic and more difficult to change shape
  • The ability to accomodate and focus on near-objects becomes imparied as we get older (presbyopia)
  • This can be corrected with glasses 


How can we remember which cranial nerve is involved in opening the eye and which in closing it?

  • Opening the eye
    • CN III 
    • the 'III' looks like pillars holding it open 
  • Closing the eye 
    • CN VII
    • 7 looks like a hook pulling the eye closed 


How many extraocular muscles are there? How many cranial nerves are the innervated by?

  • 7 muscles (6 move the eye and 1 the eyelid)
  • 3 cranial nerves 


What are the extraocular muscles and their innervation?

  • Remember LR6,SO4,R3
  • Lateral rectus 
    • CN VI (abducens)
  • Superior oblique 
    • CN4 (trochlear)
  • The rest of them are CN III (oculomotor)
    • Medial rectus
    • Superior rectus 
    • Inferior rectus 
    • Inferior oblique 
    • Levator palpibrae superioris (eyelid)


Describe the origin and insertion of the rectus muscles

  • Origin 
    • Common tendinous ring at the apex of the orbit 
  • Insertion 
    • Surface of sclera of the eyeball
      • e.g. Lateral rectus into lateral surface of sclera, medial rectus into medial surface of sclera etc.


In which direction do the lateral and medial rectus muscles move the eye?

  • Lateral rectus moves the eye laterlly in a horizontal plane 
  • Medial rectus moves the eye medially in a horizontal plane 


What occurs in palsies of the abducens nerve?

  • Lateral rectus will not move 
  • This means the eye will remain central/medial due to unopposed action of the medial rectus 


Describe the action of superior oblique

  • Moves the eye downwards when it is medial 
  • Intorts the eye 

N.B. also moves the eye down when it is central but inferior rectus will also be acting on it in this position so this is not how it is tested 


Describe the origin and insertion of superior oblique

  • Origin: apex of the orbit above the optic canal 
  • It then goes through a trochlear (like a sling)
  • Insertion: posterior superior surface of the sclera of the eyeball 


When might you get problems with vision when walking downstairs or reading?

  • When doing these acitivites the eye is medial and down and this action is caused by superior oblique (innervated by trochlear nerve)
  • So trochlear nerve palsy can present in this way 
  • (this is often the only time a problem is seen with this palsy and so it can be hard to pick up on as sometimes the patient just tilts their head slightly to compensate)


How do you test the superior and inferior rectus muscles?

  • Ask patient to look up (superior rectus) or down (inferior rectus) when the eye is lateral 


Describe the action of inferior oblique

  • Moves the eye upwards when it is medial 
  • Extorts the eye 


what is the origin and insertion of inferior oblique?

  • Origin: floor of the orbit, lateral to the lacrimal groove 
  • Insertion: inferior surface of the sclera of the eyeball 


How can you test the action of the oblique and rectus muscles?

  • Ask the patient to follow your finger whilst making a H shape 
  • This checks both eyes at the same time 


If someone is hit in the eye so increasing pressure in the orbit what happens to this pressure?

  • The pressure goes to the inferior border (maxillary floor) of the orbit as this is the weakest
  • This is known as a blow-out fracture 


What is seen in a blow-out fracture?

  • Inferior border (maxillary floor) is fractured
  • Contents of the orbit can leak out causing a tear-drop sign on MRI
  • damage to veins etc. can cause bruising 
  • The inferior rectus runs along the inferior border and it can become tethered and stuck down with the broken bit 
    • The eye becomes stuck looking down even though the muscles moving the eye upwards are still working


Describe the blood supply to the eye

  • The internal carotid gives rise to the ophthalmic artery 
  • This gives rise to:
    • Central retinal artery 
      • runs through optic nerve to supply retina 
    • Terminal branches (end arteries)
      • If blood supply is disrupted this can cause necrosis


what does central retinal artery occlusion appear as on a fundus?

  • A 'cherry red spot' on a pale background


Describe th venous drainage of the eye

  • Central retinal vein 
    • Drains through the optic nerve
    • Drains to the superior ophthalmic vein which drains into the cavernous sinus 


what is seen in central retinal vein occlusion?

  • The vein can't drain so causes oedema
  • Can be caused by dehydration amongst other things


What is the conjunctiva?

  • A thin, clear film that extends up to the edge of the cornea (limbus) and is reflected onto the inner surface of the upper and lower eyelids 


What are the two parts of the conjunctiva?

  • Bulbar conjunctiva 
  • Palprebral conjunctiva 


What is conjunctivitis?

  • Infection (bacterial or viral) and inflammation of the conjuncitva
  • It appears red as blood vessels running through it dilate as it becomes inflamed 


what is the function of the eyelids?


  • To protect against injury, excessive light and dryness (especially of the cornea)
  • The eye blinks reflexively when the cornea becomes dry and the eyelids carry a film of fluid over the cornea while also sweeping any dust and foreign material across to the medial angle of the eye


What can be caused by dust/particles damaging the cornea?

  • Corneal abrasions and ulcerations
  • These are extremely painful 


What are tarsal plates?

  • dense bands of connective tissue that give the eyelids their shape and stregnthen them 
  • They contain the tarsal (Meibomian) glands


What two glands are found in the upper eyelid?

  • Tarsal gland (meibomian gland)
  • Ciliary gland 


What do the tarsal glands produce? What is inflammation of the tarsal glands called?

  • Produce oily secretions which lubricate the edge of the eyelids and mix with the tear film over the surface of the eye preventing tears from evaporating too quickly
  • Inflammation of the tarsal gland:
    • Meibomian cyst
    • Painful 
    • Causes swelling in the eyelid 


What is a stye? How can it be treated?

  • Inflammation of the ciliary gland due to infection 
  • Can treat with antibiotics or warm compress and warm salty water 


Why is complete ptosis and a down and out position of the eye seen in CN III lesions?

  • Complete ptosis
    • paralysis of levator palpebrae superioris 
  • Down and out due to paralysis of extra-ocular muscles except:
    • Lateral rectus (out)
    • Superior oblique (down)


What is the action of obicularis oculi? What is its innervation?

  • Closes the eye 
  • Innervated by CN VII (facial nerve) 


What are possible causes of nerve lesions?

  • Trauma 
  • Tumour
  • Diabetes
  • Hypertension 


what is the pupillary light reflex? What is meant by the direct and consensual reflex?

  • Constriction of the pupil in response to light 
  • If light is shined in the left eye 
    • Constriction of the left pupil (direct light reflex)
    • Constriction of the right pupil (consensual light reflex)
  • Each eye must be tested inividually whilst looking for both direct and consensual light reflexes 


What is the afferent limb of the pupillary light reflex?

  • Sensory afferent to light from the left retina (CN II) 
  • To the pretectal nucleus in the brainstem

(this just occurs on the side of the eye that the light was shined into)


What is the efferent limb of the pupillary light reflex?

  • Connection with edinger westphal nuclei on the left and right 
  • Parasympathetic fibres from the EDW nuclei leave the brain stem 
  • They hitch hike on CN III (left and right)
  • Pass via the ciliary ganglion 
  • Reach the sphincter pupillae causing constriction of the pupil 


how do we check visual acuity?

  • Do when patient is wearing their normal glasses
  • Near vision (30cm): record smallest print they can read
  • Distance vision:
    • Use a snellen chart
    • 6 metres away 
    • Recorded as 6/x (top number is distance at which the test is made, bottom number is row number that the patient can read)
  • Also check CNII (optic) using ichihara plates to check for colour vision 
  • Check visual fileds by comparing the patient's fields to your own


What is visualisation of the retina using an ophthalmoscope called? what should the conditions be like? How do you carry it out? What is the red reflex? How do we see the macula?

  • Fundoscopy 
  • Room should be dark 
  • Should start at 30cm from patient and 15 degrees from line of fixation then gradually move towards the eye 
  • When at 30cm the pupil should appear pink- this is the red reflex 
  • Ask the patient to look straight at the light to view the macula


If there is no red reflex in children, what might this be a sign of?





What does this x-ray show?

  • Blow-out fracture with teardrop sign 








What can drainage of the aqueous humour from the anterior segment of the eye be impeded by?

  • A blockage in the trabecular meshwork
  • Or if the iris is pushed forwards so blocking the irido-corneal angle 


Why is it impossible to lose a contact lens behind the eye?

  • The conjunctival membrane reflects off the sclera to line the inner surface of the eyelids
  • It cannot extend beyond the margin of this reflection 


What is the difference between papiledema and optic disc cupping?

  • Papilloedema
    • Caused by increased intra-cranial pressure
    • Usually bilateral
    • Optic nerve is surrounded by dura and CSF. If there is increase in pressure in the brain/CSF this compresses the nerve preventing axoplasmic flow and causes the nerve to swell
    • Optic disc appears swollen with blurry edges
  • Cupping
    • Caused by raised intra-ocular pressure e.g. glaucoma
    • Increased diameter of the disc 
    • Disc doesn't appear swollen and the margins are still well defined 


What can cause raised intra-cranial pressure?

  • Haemorhage
    • Intra-cerebral
    • Extra-dural 
    • Sub dural 
  • Brain tumour 


As well as papiloedema what else can cause swelling of the optic disc?

  • Optic neuritis (inflammation of the nerve)


Why is the cornea not affected in conjunctivitis?

  • The conjunctivae ends at the limbus so does not overly the cornea 


What is the location of the tarsal and sebaceous (ciliary) glands?

  • Tarsal 
    • Posterior to eyelash within the tarsal plates (eyelid)
  • Sebaceous gland 
    • At base of eyelash (lash follicle)


In a blow-out fracture the infra orbital nerve (branch of trigeminal) can be damaged. What does this lead to?

  • Reduced sensation over the cheek 


Why is suturing of a wound of the medial angle of the eye not straightforward?

  • May involve damage to lacrimal canaliculi or nasolacrimal ducts 
  • Suturing here can cause stenosis of the lacrimal drainage system directly beneath it and the patient can be left with long term problems:
    • Excessive tearing 
    • Recurrent conjunctivitis due to impedence of tear drainage
  • Stents can be used to make sure it remains patent as the wound heals 


What effects would there be on lacrimation if there is damage to the obicularis oculi?

  • It is a sphincter surrounding the palprebral fissure
  • When it contracts tears are swept across the eye from lateral to medial allowing lubrication and the removal of foreign bodies
    • Damage may stop eye closing so stop it from effectively lubricating and protecting the surface of the eye 
    • Weakness of the muscle can cause the lower eyelid to fall away from the eye causing pooling of tears in the lower fornix and creating an environment for potential infection 
    • Causes lack of protection to cornea which can dry out and ulcerate


What can blockage secondary to thrombosis before the central retinal artery divides into its small branches in the retina cause?

Instant, painless loss of vision due to ischemia to all tissues distal to the site of blockage 


Why can thrombophlebitis of facial veins spread into the interior of the cranial cavity?

  • Facial veins connect to cavernous sinus via ophthalmic veins 
  • Veins are valveless so blood can travel both ways
  • In thrombophlebitis of facial vein blood clots may pass into the intracranial venous system


Why can damage to the ophthalmic division of the trigeminal nerve be dangerous to the eye?

  • it provides sensation to the conjunctiva and cornea so damage leads to loss of corneal reflex
  • Any dust/grit will not be felt so can lead to corneal injury, ulceration and scarring


Why can reactivation of the varicella (herpes) zoster virus (from previous chicken pox) infection involving the ophthalmic division of the trigeminal be sight threatening?

  • Ophthalmic shingles
  • The rash, while affecting the skin innervated by the ophthalmic division can also involve the conjunctiva and cornea causing inflammation