Sir,

We read with great interest the letter by Jamison and Gilmour,1 and wish to emphasise that patients with headache and cotton wool spots require appropriate investigation before using the diagnosis of exclusion ‘retinal vasospasm’, as the differential diagnosis is wide and has potential threat to sight or life. This includes ischaemic retinopathy (diabetes, hypertension, hypercoagulable states, embolic disease), inflammatory conditions (systemic lupus erythematosus, polyarteritis nodosa, giant cell arteritis), and more rarely infection (HIV, Bartonella, leptospirosis) and neoplasia (lymphoma, leukaemia, metastases).

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