Thyroid eye disease (TED) is an autoimmune condition in which the immune system becomes mistakenly activated against the patient’s own orbital tissues, causing inflammation and swelling. TED is relatively rare, affecting around 25 of every 100,000 people in the UK, so optometrists may not see many cases in their careers. However, TED is important because it is a very distressing condition that can threaten eyesight and alter facial appearance enough to cause permanent disfigurement if not treated. This review aims to inform readers about TED, and in particular to enable optometrists to recognise TED, to advise patients and recommend supportive treatment, to make appropriate onward referrals and to identify some of the treatments patients may receive after specialist referral.