Applied Anatomy of the Eye Flashcards
Give 6 causes of blindness and state which is the most common
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%)
Explain how a history of the eye should be taken
List the structures, front to back, that should be examined
What 5 things must we test in an eye examination?
1) best visual acuity
2) colour vision
3) field of vision
4) pupil reactions
5) appearance
What 4 tests, will assess CN II?
1) best visual acuity
2) colour vision
3) field of vision
4) pupil reactions
What 3 cranial nerves have eye motor functions?
II, III, IV, VI (2,3, 4,6)
What is ‘visual acuity’ and explain how we assess this
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’
Explain how we assess ‘colour vision’
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)
State what the term for each of the following visual defects is
How do we assess ‘Field of Vision’ and explain how this is done
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
What 2 stimuli does the pupil respond to?
light and accommodation
What NS control is contriction vs dilation of the pupil under?
State what the response of a healthy eye would be to light
Constriction = Parasympathetic
Dilation= Sympathetic
A healthy eye constricts with exposure to light
What would a healthy accommodation test show?
A healthy eye constricts and converges for near objects
Briefly explain the PNS pathway + response to light shone in the LEFT eye
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
What 5 things are we assessing in pupil reactions?
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)
What is RAPD?
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
Describe how you would test RAPD
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
Describe and explain a negative RAPD test
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
Describe and explain a positive RAPD test
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
What is Orbit Proptosis? (NOT Ptosis)
How must we observe the patient?
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
Give 4 causes of Orbit Proptosis
1) Infection (orbital cellulitis)
2) Inflammation (Thyroid eye)
3) Vascular abnormalities
4) Bony abnormalities
5) Tumours
What is the difference between proptosis and exopthalmus?
Proptosis can describe any organ that is displaced forward, while exophthalmos refers to only the eyes
What portable device can be used to look at optic nerves and why is it good?
Direct Ophthalmoscope: has very high magnification
What 2 things should we ideally have to use an ophthalmoscope?
1) Darkened room
2) Dilated pupils
How do we use an ophthalmoscope?
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
What 3 filters can we have on an ophthalmoscope?
State what colour structures appear and what each may be useful for?
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
What is the range of measurement for Intraocular Pressure?
What does a higher pressure increase risk of?
Range: 10 – 22
High pressure = risk of glaucoma
Give 4 problems that can occur with the eyelid and explain these
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
Give 2 neurogeneic causes of Ptosis
1) 3rd Nerve Palsy
2) Horners
Give 2 myogenic causes of ptosis
1) myotonic dystrophy
2) myasthenia Gravis
Give 3 other causes of ptosis (+ examples)
1) Aponeurotic: ie. age related
2) Mechanical: oedema/tumors
3) Traumatic
What is Horners Syndrome and give the triad of symptoms
Damage to the sympathetic pathway
Triad: Ptosis, Miosis, Anhidrosis
Explain how hydroxyamphetamine can be used to determine a pre vs post-ganglionic lesions in Horners
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
Explain how cocaine can be used to asess Horners syndrome
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
Describe the 3 types of conjunctivitis and clinical features of each
1) Bacterial: unilateral/bilateral, purulent
2) Viral: unilateral then bilateral, watery, gritty
3) Atopic: bilateral, itchy, watery
What is a sub conjunctiva haemorrhage?
Small amount of blood in the conjunctiva due to shearring of small blood vessels
looks scary… BUT usually not dangerous
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?
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!!
Give 2 problems that can occur with the Sclera
1) Episcleritis
2) Scleritis: inflammation causes sclera to thin away, appears blue due to the dark choroid underneath
Give 4 problems which can occur with the cornea
1) Corneal abrasion: break in the epithelium of the cornea
2) Bacterial Ulcer
3) Herpetic ulcer
4) Foreign body
5) Keratoconus/hydrops
Give 3 problems which can occur within the anterior chamber
1) Uveitis
2) Hypopyon: precipiating white blood cells which can be sign of severe uveitis or infection
3) Hyphaema
What common problem may occur with the lens?
Cataracts: opacification of the lens, appears cloudy
Give 3 problems which may occur with the retina
1) Retinal Detachment
2) Central Retinal Artery Occlusion
3) Central Retinal Vein Occlusion
What is the key presentation of retinal detachment?
1) Flashes, floaters, curtain-like loss of vision
2) If extensive ➞ RAPD
3) Elevated retina +/- folds
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?
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
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
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
Give 4 risk factors for central retinal vein occlusion
1) Age
2) HTN
3) arteriosclerotic vascular disease
4) conditions that increase blood viscosity (polycythemia vera, sickle cell disease, lymphoma, leukemia)
What would be seen in dry ARMD?
Deposits of lipofuscin within the retina
Slowly progressive
What would be seen in wet ARMD?
How would the patient present and how would you treat?
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
How can we easily assess whether a person is a risk of macula degeneration?
Amsler grid
What is the leading cause of blindness amoung working age adults?
How does this present?
Diabetic Retinopathy: caused by end organ damage of diabetes leading to progressive damage to retinal vessels
Presents as Dots, Blots and Cotton Wool Spots
Describe the patho of Diabetic Retinopathy
Explain why angiogenesis occurs in diabetic retinopathy and how we can treat?
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
What is glaucoma and give the 3 types
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
What is Acute Angle Closure?
Give 6 symptoms
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!!
What is Papilloedema?
Optic disc swelling caused by raised intracranial pressure
Almost always bilateral (except in very unusual cases)
What is Giant Cell Arteritis?
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
What are the criteria required to be diagnosed with Giant Cell Arteritis?
3/5 of the following:
- Age ≥ 50
- New Headache
- Temporal artery abnormality
- Raised ESR ≥ 50
- Abnormal biopsy of Temporal Artery
