Pathophysiology
Central retinal artery occlusion occurs when we have impaired blood flow through the central retinal artery (branch of the ophthalmic artery which is a branch of the ICA). It is essentially a “stroke of the eye”.
It is caused by:
- Thromboembolism - due to atherosclerosis
- Giant cell arteritis
🏘 Epidemiology
It is relatively rare. It occurs less frequently than central retinal vein occlusion.
⚠️ Risk factors
- Increasing age
- Obesity
- Family history
- Smoking
- Alcohol consumption
- Hypertension
- Diabetes
- Poor diet
- Inactivity
The risk factors are pretty much the same for atherosclerosis as ultimately that is what will cause CRAO in most cases.
The risk factors for giant cell arteritis is white patients >50 years old. Females have a higher incidence.
😷 Presentation
- ⭐️ Sudden, painless, unilateral vision loss
- ⭐️ Relative afferent pupillary defect - the affected eye constricts less when the light is shone directly, and constricts more with the consensual/indirect response. The reason for this is that the retina that senses the light directly is ischaemic and the photoreceptors are not detecting the light changes. However, the unaffected eye is able to relay the consensual response via the Edinger-Westphal nucleus → ciliary ganglion → iris sphincter muscle for contraction.
Fundoscopy will show:
⭐️ A distinct pale retina (due to a lack of perfusion) with a cherry red spot (which is the the macula, as it has a thinner surface and shows the red coloured choroid that lies beneath it
CRAO shows a pale retina with a cherry red spot while CRVO shows a blood and thunder appearance.
CRP or ESR must be checked to ensure that it is not GCA.
🧰 Management
Acute management
Acute management is difficult and the prognosis is not good. Techniques aim to try and dislodge the thrombus but the evidence is poor.
- Intraarterial thrombolysis
- Ocular massage
- Sublingual isosorbide dinitrate
- Acetazolamide - may reduce pressure.
Long-term management
🏆 Risk factor management is ultimately the treatment of choice.