Sixty-year-old Mr. Yang was diagnosed with hyperthyroidism earlier this year and showed symptoms of protruding eyeballs and double vision. After receiving treatment from the endocrinology department, Mr. Yang’s thyroid function has basically returned to normal, but it is still uncomfortable to see things high and low. Mr. Yang wondered why the double vision still existed when all the indicators of the thyroid gland were normal. After careful examination, he was diagnosed with thyroid-related ophthalmopathy. Many people think that patients with thyroid-related eye disease must have a combination of hyperthyroidism, but this is not the case. Some patients may have only ocular signs alone, and thyroid function tests may be normal or even low. The most common clinical manifestation of the disease is blepharospasm, which is an early sign that includes enlarged lid fissures, decreased blinking, inability of the upper lid to move down with the eye when the eye is turned downward, and exposure of the sclera above. Protrusion of the eyeball and double vision are often the main reasons why patients come to the clinic. In the early stages of the disease, edema and inflammation occur in the extraocular muscles and surrounding tissues, and as the disease progresses, the extraocular muscles gradually become fibrotic, resulting in impaired eye movement and diplopia. The normal movement of the eye requires the extraocular muscles to work together, such as contraction of the superior rectus muscle and relaxation of the inferior rectus muscle when turning upward. When fibrosis occurs in the muscle, it is like an inelastic cowhide band that cannot be freely extended and shortened, and the eye movement will be impaired, resulting in the inability to synchronize the vision of both eyes, and the patient will see things with double vision. If the fibrosis of the extraocular muscles is severe, the patient will have persistent diplopia. Patients with thyroid-related ophthalmopathy with abnormal thyroid function should first be treated in the endocrinology department for the primary disease, and after six months of conservative treatment, if double vision persists, eye muscle surgery may be considered to address the eye deviation and diplopia caused by the extraocular muscle lesion. For the first six months, one eye can be masked to eliminate diplopia. Reduce water intake at bedtime, sleep with the head elevated, lie on your back, apply eye ointment at night if eyelid closure is incomplete, and use artificial tears and antibiotic eye drops as appropriate. Patients with thyroid-related eye disease should not only be prepared to live with “diplopia” for a long time, but also focus on visual acuity, intraocular pressure, and visual field. Extensive inflammatory edema of the extraocular muscles and surrounding tissues in patients with this disease can lead to increased pressure in the orbital contents, which can compress the optic nerve and lead to decreased vision or even loss of vision and visual field defects.