Acute angle closure glaucoma (AACG) is a painful, potentially blinding condition with patients frequently presenting within hours of onset with ocular pain, nausea and vomiting. Argon laser pan-retinal photocoagulation (PRP) is one of the commonest ophthalmic outpatient procedures. It is used in the treatment of vascular disorders of the retina; most commonly diabetic retinopathy. AACG following PRP is a recognised, but rarely occurring, complication. Prompt treatment alleviates pain and improves visual prognosis. The authors report a case of AACG following PRP treatment which was initially mistaken for a viral illness.