Bulging eyeballs refer to eyeball protrusion, which is usually caused by thyroid-related eye disease, tumors in the orbit, or high myopia. 1. Thyroid-related eye disease: Patients with thyroid-related eye disease may have protruding eyeballs due to hypertrophy of the extraocular muscles and fatty tissues in the orbits, which push out the eyeballs. 2. Orbital tumors: patients with orbital tumors may have eyeball protrusion because the tumor occupies the space and increases the volume of orbital contents, which pushes out the eyeball. 3. High myopia: patients with high myopia have eyeball protrusion due to the prolongation of eye axis, which causes the diameter of eyeball to expand. It is recommended that patients with prominent eyeballs should consult a doctor in time to evaluate their condition and have a reasonable treatment plan formulated by the doctor.