retinal artery occlusion (RAO)

introduction

sudden onset of relatively painless monocular vision due to ischaemia/infarction of the retina resulting from occlusion of central retinal artery blood flow which comes from the ophthalmic artery which is the 1st intracranial branch of the internal carotid artery although 14% have a cilioretinal artery anatomy
urgent Rx may restore some useful sight in ~20-30% of cases
~40% of cases are more distal occlusions of the branch retinal artery (BRAO)
5% are due to cilioretinal artery occlusions
1-2% develop bilateral occlusions
mean age is 7th decade of life
patients with RAO have a doubled risk of death within 9yrs cf age-matched population, and a life expectancy of 5.5yrs (cf 15yrs with age-matched controls)

complete occlusion of central retinal artery causes irreversible infarction of the retina after 105 minutes
whilst urgent Rx may be useful, the patient is at great risk of other pathology as these are usually the harbinger of further potentially life threatening events due to the underlying causes which should be investigated early

embolism (eg. AF, atherosclerotic carotid artery disease, endocarditis)
angiospasm
external occlusion of retinal artery
prolonged direct pressure to the globe
prolonged glaucoma
2/3rds have a PH hypertension
25% are diabetic
20% have > 60% carotid stenosis and this is the leading cause of those aged 40-60yrs
young patients tend to have IVDU endocarditis, HbS, thrombophilias such as antiphospholipid antibodies, and rarely, migraine may cause RAO
inflammatory endarteritis (rare)

sudden onset of relatively painless monocular vision
amaurosis fugax preceding persistent loss of vision suggests branch retinal artery occlusion (BRAO) or temporal arteritis
afferent pupil defect
fundoscopy with dilated pupil shows:
- tram tracking of vessels (interrupted lines)
- pale ground glass retina with cherry red macula (due to choroidal blood flow from ciliary vessels)
- emboli can be seen in 20%

contact ophthalmology reg ASAP
- consider massage of eye
- consider AC paracentesis
Mx as per acute stroke / TIA
- FBE, U&E, LFTs, CRP, ESR, Coags, glucose, HbA1c, lipids
- consider thrombolysis but be aware of risk/benefits of doing so
- further Ix and manage underlying cause:
  - ECG to exclude AF
  - CT brain
  - carotid doppler USS
  - echocardiogram
documentation that advised not to drive a car
will need ophthalmologist follow up in 2 months