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With ongoing disease, the most frequent sign is upper eyelid retraction, which affects 90–98% of patients at some stage [3, 6] and frequently varies with attentive gaze (Kocher sign) [7]. Indeed, if upper eyelid retraction is absent, then it is appropriate to question the diagnosis [7]. The contour of the retracted upper eyelid often shows lateral flare (Fig. 1) [8], an appearance that is almost pathognomonic for GO.

Exophthalmos (also known as proptosis) is also very frequent and correlates significantly with lower lid retraction [9]; these patients are more likely to show incomplete eyelid closure (lagophthalmos). Many such patients, especially those with a wide palpebral fissure, will show punctate inferior corneal staining with fluorescein [9, 10].

Double vision is rare at presentation but fairly common later, when it is initially noticed either on waking, when tired, or on extremes of gaze [4, 5, 11]. Hence, many patients presenting to tertiary centres show restriction of ocular excursions in one or more directions of gaze. Eye movements may be accompanied by aching; however, if the orbit is extremely congested, then the patient may also develop orbital ache unrelated to gaze [12].

Fig. 1. Assessment of the palpebral aperture. The midpoint of the pupil is chosen regardless of lateral flare. In this example, upper eyelid retraction and lower eyelid retraction both measure +1 mm with the limbus as a reference point. Note that the normal adult eyelid position would measure –2 mm.

Only about 5% of patients report visual symptoms such as alteration in colour perception or blurring of vision, which may be either patchy or generalized [4, 5, 11]. These visual symptoms are potentially significant markers of dysthyroid optic neuropathy (DON), and as they may not be volunteered, they should be specifically elicited from all patients with progressive or otherwise symptomatic disease as detecting subtle evidence of DON is crucial. If DON is significantly asymmetrical (30%), then an afferent pupil defect will also be apparent [13].

Sight-threatening corneal ulceration is even less common than DON, but potentially devastating. It presents as an area of corneal staining, sometimes with thinning or abscess and very occasionally perforation. Corneal ulceration can only develop when normal corneal protection is lost. This occurs in those patients who not only have lagophthalmos (see above), but whose cornea remains visible when the eyelids are closed. In 90% of normal individuals the eyeball rotates upwards on eyelid closure to protect the cornea. If the inferior rectus muscle is tight as is common in GO, then this normal reflex (the Bell’s phenomenon) is lost, leaving the cornea in a more vulnerable position (Fig. 2). It is not known whether patients with extreme eyelid retraction are at greater risk of ulceration, but it is clear that sight-threatening ulceration can develop in patients without severe eyelid retraction.

Other unusual signs and symptoms of GO include superior limbic keratoconjunctivitis, inflammation of the caruncle and/or plica (see the section “How Are These Signs Assessed?” below) and episodes of globe subluxation (where the eyeball protrudes in front of the eyelids). The latter are extremely alarming for both patient and any witnesses, but fortunately affect only 0.1% of patients [14].

Hence patients with GO can show a number of clinical signs; however, it is relatively unusual to present with all of them. Only 5% of patients had the complete constellation of classic findings: eyelid retraction, exophthalmos, optic nerve dysfunction, extraocular muscle involvement, and hyperthyroidism [15].

Fig. 2. Eyelid closure: lagophthalmos and the Bell’s phenomenon. a Open eye. b Attempted eyelid closure with lagophthalmos, but no corneal exposure due to a good Bell’s phenomenon rotating the eyeball upwards. c Attempted eyelid closure with lagophthalmos and no Bell’s phenomenon, hence corneal ulceration.