9. Neurophthalmology Flashcards
What fibres join to form the optic nerve?
1.2 million afferent fibres from retinal ganglion cells.
What are the 5 signs of Optic Nerve Dysfunction?
- Reduction in Visual Acuity
- RAPD (Relative afferent pupillary defect)
- Reduction in Light Sensitivity
- Dyschromastopsia
- Visual Field Defects
What electrophysiological examinations may be used to test optic nerve function?
Electroretinogram (ERG) = Retinal Function
Electroculogram (EOG) = Epithelium Function
Visual Evoked Potentials = CNII i.e. Cortex to Eye Function
When might electrophysiological eye tests be used?
Especially useful in unexplained visual loss, to check if CN functioning properly.
What are the Ddx for UNILateral optic disc swelling?
Optic Neuritis (Assoc with MS)
Giant Cell Arthritis
Ischaemic optic neuropathy (Assoc w/hypertension)
Compressive optic neuropathy (lymphngioma, tumour)
Orbital pathology – eg TED (thickening of tissues+structures)
Ocular pathology – posterior uveitis, scleritis
What are the Ddx for Bilateral Disc Swellings?
Papilloedema (OD swelling due to raised ICP)
Optic disc drusen (No acutally swellingCalcification of the optic disc)
What congenital condition may cause optic disc swelling?
Leber’s optic neuropathy (inherited degeneration of retinal ganglion cells)
Who is usually affected by optic neuritis?
Most common in 3rd and 4th decade
Northern Europe + Scandinavia = High Rate
W>M
What are the two types of neuritis?
Papillitis
Retrobulbar
What is the appearance of most cases of retrobulbar optic neuritis?
Optic disc looks normal cause the inflammation is behind
What is the most common type of optic neuritis?
Retrobulbar
Most caused by demyelinating disease.
Which disease has a strong association with optic neuritis?
MS
75% of definite MS patients will experience optic neuritis.
What are the signs and symptoms of optic neuritis?
Colours Become Washed-out/dull
Pain on Eye Movement
Decline in Vision
What is the key test to be performed if you suspect optic neuritis?
MRI to detect demyelination/MS
What is the usual clinical course of optic neuritis?
Most get spontaneous visual recovery in 2-3 months.
But often not full.
What is the Tx for optic neuritis?
Tx with steroids speeds up visual recovery, but does not alter final visual outcome.
3 days High Dose IV Oral follow.
(Controversial. Cochrane Review. Not much benefit in MS patients and poor evidence, but a lower threshold for IV steroids for others)
What is giant cell arthritis? What is it AKA?
Inflammatory disease of blood vessels most commonly involving large and medium arteries of the head, predominantly the branches of the external carotid artery.
Affect primarily medium and large arteries.
Systemic so affect other vessels inc aorta/cornoary vessels
Ischaemic Type Arthritis
What is the most serious complication of GCA?
Occlusion of the ophthalmic artery, a medical emergency which can cause irreversible ischema and blindness if not treated promptly.
What are the symptoms of GCA?
Symptoms can be quite vague…
Headache scalp tenderness (combing, pillow, haridressers)
Unilateral headache
Jaw lock/pain= claudication due to involvement of masseter mucles/masseter artery.
Visable temporal arteries but they are non-pulsatile
In whom is GCA more common?
Much more common in 70yo+
With what disease is GCA associated?
Assoc with polyneuropic myalgia, many have hx of system symptoms (generally unwell, fevers, specific arthritic symptoms)
What are useful tests for GCA?
Tests that help = Inflam markers ESR/CRP/IgG in men = 1/2 age, women 1/2age+10
What is NAION?
Non Arthritic Ischemic Optic Neuropathy
NAION results from the coincidence of cardiovascular risk factors in a patient with “crowded” optic discs.
In whom is NAION more common?
Affects younger people compared with AION.
40-65
What are the risk factors for AION?
DISC
Small crowded discs “disc at risk” (more likely to have circulatory compromise or sudden hyper/hypotensive event )
CARDIOVASCULAR
Sudden hypotensive event
Diabetes, HTN, atherosclerosis, Smoking etc
What is the mechanism of action during NAION?
Mechanism – probably occlusion / impaired circulation in short posterior ciliary arteries – resulting in partial or complete infarction of optic nerve head.
What are the clinical signs of NAION?
- RAPD
- Unilateral disc swelling (acute) – often sectoral, often pale nerve later (chronic)
- Second eye may become involved later
- Visual field defect – often “altitudinal” (Affects the sup part Of the disc more often)
- ESR may be raised (but to a lesser extent than AION)
What is the Tx for NAION?
Exclude GCA
Controlling Risk Factors