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Dr Geraint Preest, Clinical Section Editor at BMJ OnExamination, gives you some hints and tips for sudden visual loss.
Acute eye problems crop up in the AKT exam quite often. The topic of Sudden Visual Loss is very popular. I’m going to go through six topics with you today;
Giant Cell Arteritis
Retinal Artery Occlusion
Giant cell arteritis is an important cause of visual loss. There are a few important points to bear in mind with this. The first is that it’s a sudden eye loss. It tends to occur in people over the age of 50. The important investigations are the ESR and CRP. When you are interpreting the ESR result, the upper limit of normal for men is half the age. The upper limit of normal for women is half the age plus ten. If you are using ESR and CRP to diagnose Giant Cell Arteritis, then it has a 99.2% sensitivity. The full blood count can also give you important clues of Giant Cell Arteritis. If a patient has a thrombocytosis, then the risk of Giant Cell Arteritis is six times greater. The biopsy result is unaffected by treatment with steroids, so don’t delay treatment before getting a biopsy.
More causes of sudden eye loss. If you’re sitting an exam, Amaurosis Fugax is another possibility. When you are trying to work out the diagnosis, think about the risk factors because these are really important. When you’re looking at the lead-in; look for hypertension, diabetes, elevated lipids, thrombophilia. Giant Cell Arteritis can present in a very similar fashion.
Another cause of eye loss is Retinal Artery Occlusion. With this, the loss is sudden and painless. There is a fix scotoma. Again consider risk factors; elevated blood pressure, elevated lipids, diabetes, thrombophilia.
Another cause of eye loss is Papilloedema. There are many causes for Papilloedema; idiopathic intracranial hypertension is one of them. There a 20 times risk if a patient is obese. Be aware of any neurological signs or signs of infection.
Optic Neuritis is another cause of visual loss. It's usually unilateral and sudden. The age range is in patients between the age of 20 and 50 usually and it presents with a retrobulbal pain and decreased colour perception, so look for this in the history. There's a relative afferent pupillary defect. What that means that when you are alternating a light between two pupils, when it goes from the unaffected eye to the affected eye, the affected eye constricts less so it appears to dilate. 70% of patients with Optic Neuritis, will have MS and for some patients it a first presentation of MS.
Finally, Retinal Detachment is another cause of visual loss. With Retinal Detachment it often presents with flashes and floaters. There is often a gradual reduction in peripheral vision and patients sometimes describe it as a curtain or a shadow coming down. When you are looking at an examination question, there may be some clues as to Retinal Detachment. It’s more common in patients over the age of 50. There may be a past medical history of Retinal Detachment or a family history of Retinal Detachment. It’s more common in extreme myopes and it’s often seen in association with a history of recent eye surgery.
In recent feedback from the Royal College of General Practitioners about the April 2016 AKT exam, they mentioned eye problems as an area of poor performance. We have listed a few common causes of visual loss and these have come from a reference from the Australian College of General Practitioners.
Sudden Loss of Vision - History and examination (External Site)
Sudden Loss of Vision - Investigation and management (External Site)