6.2 Applied Anatomy of the Eye

Question 1

Give 6 causes of blindness and state which is the most common

Answer 1

1) cataracts (47.9%)
2) glaucoma (12.3%)
3) age-related macular degeneration (8.7%)
4) corneal opacity (5.1%)
5) diabetic retinopathy (4.8%)
6) childhood blindness (3.9%)
7) trachoma (3.6%)

Question 2

Explain how a history of the eye should be taken

Answer 2

Question 3

List the structures, front to back, that should be examined

Answer 3

Question 4

What 5 things must we test in an eye examination?

Answer 4

1) best visual acuity
2) colour vision
3) field of vision
4) pupil reactions
5) appearance

Question 5

What 4 tests, will assess CN II?

Answer 5

1) best visual acuity
2) colour vision
3) field of vision
4) pupil reactions

Question 6

What 3 cranial nerves have eye motor functions?

Answer 6

II, III, IV, VI (2,3, 4,6)

Question 7

What is ‘visual acuity’ and explain how we assess this

Answer 7

How well the individual can resolve detail

Snellen Chart:

• Read at 6 metres (or look on chart)
• Distance glasses on!
• Right eye then left eye
• Then repeat with pinhole (eliminates refractive error)

Chart tells us: ‘You can see at 6 metres what a normal person can read at ___ metres’

Question 8

Explain how we assess ‘colour vision’

Answer 8

Ishihara Plates: usually used to assess congential defects (less used for nerve lesions)

• Use at 2/3m in good light, each eye in turn
• Glasses to suit patient

Vision >6/18 is good (less than 6/18 means patient will see blurring)

Question 9

State what the term for each of the following visual defects is

Answer 9

Question 10

How do we assess ‘Field of Vision’ and explain how this is done

Answer 10

Confrontation visual field:

1) Both eyes open, patient looking at bridge of examiner’s nose
* Ask if any part appears missing - gross homonymous defects
2) Patient to cover each eye in turn, examiner keeps opposite eye open, position the target equidistant between examiner and patient

• Move from unseen to seen (peripheral to central)
• Ideally a white pin for peripheral defects, red for central 30 degrees

3) Map out physiological blind spot (red pin ideally)
* Can be enlarged in optic nerve swelling

Question 11

What 2 stimuli does the pupil respond to?

Answer 11

light and accommodation

Question 12

What NS control is contriction vs dilation of the pupil under?

State what the response of a healthy eye would be to light

Answer 12

Constriction = Parasympathetic

Dilation= Sympathetic

A healthy eye constricts with exposure to light

Question 13

What would a healthy accommodation test show?

Answer 13

A healthy eye constricts and converges for near objects

Question 14

Briefly explain the PNS pathway + response to light shone in the LEFT eye

Answer 14

Light shone in LEFT eye ➞ message sent via optic nerve (CN II) to pretectal nucleus ➞ Edinger–Westphal nucleus ➞ sends reaction back to BOTH eyes through CN III to cause constriction

Vice versa for light shone in right eye

Question 15

What 5 things are we assessing in pupil reactions?

Answer 15

Ask patient to look at distant target:

1) Observe: Pupils equal?
2) Direct: constriction of ipsilateral eye (the pupil should constrict on direct light)
3) Consensual: constriction of contralateral eye (the pupil should constrict on shining light on the other eye)
4) Accommodation: pupils should constrict when focusing on near target
5) Relative Afferent Pupillary Defect (RAPD)

Question 16

What is RAPD?

Answer 16

Relative Afferent Pupillary Defect

This is a condition in which pupils respond differently to light stimuli shone in one eye at a time due to unilateral or asymmetrical disease of the retina or optic nerve

Question 17

Describe how you would test RAPD

Answer 17

1) Keep the lights low for maximum reaction
2) Focus at distance (reduce accommodation)
3) Shine light on right eye
5) Swing light across to left eye

Move the whole torch deliberately from side to side so that the beam of light is directed directly into each eye, pause for 2 seconds at each

Question 18

Describe and explain a negative RAPD test

Answer 18

Each pupil should constrict quickly and equally during exposure to direct light and to light directed at the other pupil (consensual light reflex)

Between swings (no direct light) both pupils should dilate

Question 19

Describe and explain a positive RAPD test

Answer 19

When light is shone on the unaffected eye both should constrict (as normal because consensual reflex is still present in THAT eye)

BUT when light is shone in the affected pupil after being shone in the healthy pupill it will remain dilated because the afferent stimulus is reduced relative to other eye

Question 20

What is Orbit Proptosis? (NOT Ptosis)

How must we observe the patient?

Answer 20

Eyes protruding from orbit (lid pulled back, eye pushed forwards). As the orbit is a fixed space, stuff behind the eyeball will push eyeball out

Observe patient from above, looking down over brow

Question 21

Give 4 causes of Orbit Proptosis

Answer 21

1) Infection (orbital cellulitis)
2) Inflammation (Thyroid eye)
3) Vascular abnormalities
4) Bony abnormalities
5) Tumours

Question 22

What is the difference between proptosis and exopthalmus?

Answer 22

Proptosis can describe any organ that is displaced forward, while exophthalmos refers to only the eyes

Question 23

What portable device can be used to look at optic nerves and why is it good?

Answer 23

Direct Ophthalmoscope: has very high magnification

Question 24

What 2 things should we ideally have to use an ophthalmoscope?

Answer 24

1) Darkened room
2) Dilated pupils

Question 25

How do we use an ophthalmoscope?

Answer 25

1) Start at “0”, or dial in the refractive prescription
2) your right eye to patients right eye and your left eye to patients left eye
3) Follow the red reflex and get in close
4) Follow vessels back to the optic disc

Question 26

What 3 filters can we have on an ophthalmoscope?

State what colour structures appear and what each may be useful for?

Answer 26

1) Red free (green) filter

• makes blood and blood vessels black
• ▪useful for seeing haemorrhages or new vessels

2) Cobalt blue filter

• makes fluorescein drops glow green
• useful for finding corneal epithelial defects

3) Slit beam
* useful for looking at the anterior chamber/cornea

Question 27

What is the range of measurement for Intraocular Pressure?

What does a higher pressure increase risk of?

Answer 27

Range: 10 – 22

High pressure = risk of glaucoma

Question 28

Give 4 problems that can occur with the eyelid and explain these

Answer 28

1) Cellulitis: preseptal vs orbital Cellulitis (dangerous)
2) Entropion: lashes rub against lower part of eye, if untreated front of eye can can wear away resulting in scarring and infections
3) Shingles: V1 of Trigeminal n ➞ Hutchinson’s sign
4) Blepharitis: edges of eyelids become inflammed
5) Chalazion: blocked duct
6) Dacrocystitis: infection of the lacrimal sac due to a blockage in the nasolacrimal duct

Question 29

Give 2 neurogeneic causes of Ptosis

Answer 29

1) 3rd Nerve Palsy
2) Horners

Question 30

Give 2 myogenic causes of ptosis

Answer 30

1) myotonic dystrophy
2) myasthenia Gravis

Question 31

Give 3 other causes of ptosis (+ examples)

Answer 31

1) Aponeurotic: ie. age related
2) Mechanical: oedema/tumors
3) Traumatic

Question 32

What is Horners Syndrome and give the triad of symptoms

Answer 32

Damage to the sympathetic pathway

Triad: Ptosis, Miosis, Anhidrosis

Question 33

Explain how hydroxyamphetamine can be used to determine a pre vs post-ganglionic lesions in Horners

Answer 33

Causes release of NA from intact nerve endings, so causes pupil dilation

1 hour post eye drops to both eyes:

• If both pupils dilate 1st or 2nd order neurone problem
• If the small pupil fails to dilate, it’s a 3rd order neurone problem

Question 34

Explain how cocaine can be used to asess Horners syndrome

Answer 34

Blocks reuptake of NA at synaptic cleft

So if there is some intact sympathetic innervation, the pupil will dilate BUT If there isn’t sympathetic innervation there will be no/minimal dilation because there is no/Little NA

Question 35

Describe the 3 types of conjunctivitis and clinical features of each

Answer 35

1) Bacterial: unilateral/bilateral, purulent
2) Viral: unilateral then bilateral, watery, gritty
3) Atopic: bilateral, itchy, watery

Question 36

What is a sub conjunctiva haemorrhage?

Answer 36

Small amount of blood in the conjunctiva due to shearring of small blood vessels

looks scary… BUT usually not dangerous

Question 37

Are alkali or acid chemical injurys to the eye worse?

What determines the extend of injury and what is the first thing you MUST do?

Answer 37

Alkali is more dangerous because it melts through the front of the eye

Extent of injury is determined by duration and extent of contact

Remember… Irrigation is key!!

Question 38

Give 2 problems that can occur with the Sclera

Answer 38

1) Episcleritis
2) Scleritis: inflammation causes sclera to thin away, appears blue due to the dark choroid underneath

Question 39

Give 4 problems which can occur with the cornea

Answer 39

1) Corneal abrasion: break in the epithelium of the cornea
2) Bacterial Ulcer
3) Herpetic ulcer
4) Foreign body
5) Keratoconus/hydrops

Question 40

Give 3 problems which can occur within the anterior chamber

Answer 40

1) Uveitis
2) Hypopyon: precipiating white blood cells which can be sign of severe uveitis or infection
3) Hyphaema

Question 41

What common problem may occur with the lens?

Answer 41

Cataracts: opacification of the lens, appears cloudy

Question 42

Give 3 problems which may occur with the retina

Answer 42

1) Retinal Detachment
2) Central Retinal Artery Occlusion
3) Central Retinal Vein Occlusion

Question 43

What is the key presentation of retinal detachment?

Answer 43

1) Flashes, floaters, curtain-like loss of vision
2) If extensive ➞ RAPD
3) Elevated retina +/- folds

Question 44

Describe the presentation of central retinal artery occlusion

Why MUST we be aware of this condition and what is the characteristic feature on an opthalmascope?

Answer 44

Sudden painless and often severe visual loss

!!! permanent damage can occur due to prolonged interruption of retinal arterial blood flow

Characteristic “cherry-redspot ” on opthalmascope

Question 45

What would be seen in central retinal vein occlusion on an opthalmascope?

What type of vision loss would the patient experience and what is this condition a major risk factor for

Answer 45

Opthalmoscope: disc swelling, venous engorgement, cotton-wool spots and diffuse retinal hemorrhage

Subacute loss of vision

Patient will be at a long term risk for neovascular disease

Question 46

Give 4 risk factors for central retinal vein occlusion

Answer 46

1) Age
2) HTN
3) arteriosclerotic vascular disease
4) conditions that increase blood viscosity (polycythemia vera, sickle cell disease, lymphoma, leukemia)

Question 47

What would be seen in dry ARMD?

Answer 47

Deposits of lipofuscin within the retina

Slowly progressive

Question 48

What would be seen in wet ARMD?

How would the patient present and how would you treat?

Answer 48

Fluid/blood within the retina due to breakthrough of vessels from the choroid

Patient would experience a sudden reduction in vision

Treated with intravitreal injections anti-VEGF

Question 49

How can we easily assess whether a person is a risk of macula degeneration?

Answer 49

Amsler grid

Question 50

What is the leading cause of blindness amoung working age adults?

How does this present?

Answer 50

Diabetic Retinopathy: caused by end organ damage of diabetes leading to progressive damage to retinal vessels

Presents as Dots, Blots and Cotton Wool Spots

Question 51

Describe the patho of Diabetic Retinopathy

Answer 51

Question 52

Explain why angiogenesis occurs in diabetic retinopathy and how we can treat?

Answer 52

Because the vessels in the eye are getting damaged due to the retinopathy, the eye isn’t getting enough oxygen. It combats this by trying to make new blood vessels ➞ angiogenesis

Treat using Panretinal Photocoagulation: this is a type of lazer which damages the peripheral retina to reduce oxygen demand, and attempts to save central retina/macula by reducing angiogenesis

Question 53

What is glaucoma and give the 3 types

Answer 53

High intraocular pressure leads to progressive thinning of nerve fibres at the optic disc (optic neuropathy). As a result patients gets progressive loss of their visual field

Types

• Open angle
• Closed angle
• Secondary to other problems in the eye

Question 54

What is Acute Angle Closure?

Give 6 symptoms

Answer 54

Severe form of closed angled glaucoma: If trabecular meshwork completely blocks, suddent high pressure builds up within the eye until the iris becomes paralysed

Symptoms: vomiting, pain, blurred sision, haloes, fixed, distorted mid dilated pupil, shallow anterior chamber, cloudy cornea, abdominal pain

Medical emergency!!

Question 55

What is Papilloedema?

Answer 55

Optic disc swelling caused by raised intracranial pressure

Almost always bilateral (except in very unusual cases)

Question 56

What is Giant Cell Arteritis?

Answer 56

This is a vascultis (inflammation of blood vessels). Can cause swelling and thickening of the temporal artery which results in a temporal headache and extreme pain

It is rapidly progressive and can cause bilateral Ischaemic Optic Neuropathy

Question 57

What are the criteria required to be diagnosed with Giant Cell Arteritis?

Answer 57

3/5 of the following:

• Age ≥ 50
• New Headache
• Temporal artery abnormality
• Raised ESR ≥ 50
• Abnormal biopsy of Temporal Artery