Ophthalmology #3 Flashcards
What is the strongest risk factor for developing dry age-related macular degeneration out of the following: Hypertension Poor diet Smoking Diabetes Mellitus Alcohol excess
Smoking
Which eye drops are used to confirm a Horner’s pupil?
What is the mechanism?
Apraclonidine eye drops
Apraclonidine stimulates alpha-1 and alpha-2 receptors. When added to the affected eye, it causes pupil dilation by >2mm because of relative supersensitivity of this pupil to alpha-1 receptor activity.
In a normal pupil, it causes constriction due to the more potent activity at the alpha-2 receptor which triggers reuptake of noradrenaline in the synaptic cleft.
After using Apraclonidine eye drops to confirm Horner’s pupil, what is Hydroxyamphetamine used for?
Hydroxyamphetamine is used to distinguish between first/second or third order neurones.
-> it will distinguish either a lesion in the brainstem, cervical cord, chest or next and one affecting above the superior cervical ganglion at the carotid bifurcation.
A normal pupil or a first/second order Horner’s pupil will dilate secondary to increased levels of noradrenaline released from the post-synaptic neurones.
In a third order neurone, this will not occur.
What is meant by a ‘first order neuron’ in relation to determining the cause of a Horner’s pupil?
Central (First Order Neuron) Horner's: - Anhydrosis of the face, arm and trunk Includes: - Stroke - Syringomyelia - Multiple Sclerosis - Tumour - Encephalitis
What is meant by a ‘Second Order Neuron’ in relation to determining the cause of a Horner’s pupil?
Preganglionic (Second Order Neuron) Horner's: - Anhydrosis of the face Includes: - Pancoast's Tumour - Thyroidectomy - Trauma - Cervical rib
What is meant by ‘Third Order Neuron’ or ‘Postganglionic Lesion’ in relation to determining the cause of a Horner’s pupil? /
Third Order Neuron (Postganglionic) Lesion: - No anhidrosis Includes: - Carotid artery dissection - Carotid aneurysm - Cavernous sinus thrombosis - Cluster headache
If ‘heterochromia’ is a feature of Horner’s syndrome, what does this tell you?
Heterochromia (difference in iris colour) is seen in congenital Horner’s.
What are the 4 cardinal features of Horner’s syndrome?
- Miosis (small pupil)
- Ptosis
- Anhidrosis (loss of sweating on one side)
- Enophthalmos (sunken eye)
- > in reality, the appearance is due to a narrow palpebral aperture rather than true enophthalmos
A patient has optic atrophy. What would you see on fundoscopy?
A pale, well demarcated disc.
Usually bilateral.
Causes a gradual loss of vision.
List some acquired causes of Optic Atrophy.
- Multiple Sclerosis
- Papilloedema (long standing)
- Raised intraocular pressure (glaucoma, tumour)
- Retinal damage (choroiditis, retinitis pigmentosa)
- Ischaemia
- Mitochondrial disorders (eg. Leber’s optic atrophy)
- Wolfram’s Syndrome (aka DIDMOAD): the association of Diabetes Insipidus, Diabetes Mellitus, Optic Atrophy and Deafness
A 34yo female attends A&E. Confused over the last 3 days.
Longstanding history of psoriasis.
Basic obs are normal. CT head unremarkable.
Fundoscopy reveals bilateral papilloedema.
What is the likely cause?
- Encephalitis
- Brain abscess
- Primary brain tumour
- Vitamin A toxicity
- Hydrocephalus
Vitamin A toxicity
- a rare cause of papilloedema
- Pt is likely to have been taking retinoids for psoriasis.
Notes:
- Encephalitis doesn’t usually present with papilloedema.
- All other options are less likely as CT head is normal.
Describe ‘papilloedema’.
Optic disc swelling that is caused by increased intracranial pressure. It is almost always bilateral.
What features might you see on fundoscopy of a patient with papilloedema?
- Venous engorgement
- Loss of venous pulsation
- Blurring of the optic disc margin
- Elevation of optic disc
- Loss of the optic cup
- Paton’s lines: concentrical / radial retinal lines cascading from the optic disc.
List some causes of papillodema.
- Space occupying lesion: neoplastic, vascular
- Malignant hypertension
- Idiopathic intracranial Hypertension
- Hydrocephalus
- Hypercapnia
Rare causes include:
- Hypoparathyroidism
- Hypocalcaemia
- Vitamin A toxicity.
A 71yo man who has recently been diagnosed with macular degeneration asks for advice regarding antioxidant dietary supplements. Which of the following may contraindicate the prescription of such supplements?
- Current smoker
- Pernicious anaemia
- Treated hypertension
- History of depression
- Previous episodes of tendonitis
Current smoker
- Beta-carotene has been found to increase the risk of lung cancer and hence antioxidant dietary supplements are not recommended for smokers.
Dorzolamide eye drops are given to a 67yo male who is known to have raised intraocular pressure (glaucoma). What is the mechanism of action of this drug?
Carbonic Anhydrase inhibitor.
How might a patient with Optic Neuritis present?
Typically a unilateral decrease in visual acuity over hours or days. There may be poor discrimination of colours and eye pain on movement.
Which one of the following is associated with the Holmes-Adie pupil?
- Decreased ankle reflexes
- Pupillary constriction
- Ptosis in 10 - 20% of cases
- Increased risk of developing MS
- Neurosyphilis
Decreased ankle reflexes
Holmes-Adie syndrome:
Association of Holmes-Adie pupil with absent ankle/knee reflexes.
What is a ‘Holmes-Adie’ pupil?
A benign condition most commonly seen in women. It is one of the differentials of a dilated pupil.
