Keep an Eye Out 

A common symptom of Graves' Disease is Graves' opthalmopathy. The signs of Graves' opthalmopathy include excessive tearing, dry or irritated eyes, bulging eyes (or exophthalmos), a gritty sensation in the eyes, pain or pressure, puffy or swollen eyelids, redness or inflammation, sensitivity to light, double vision and a reduction in eye movement. In very rare cases, Graves' opthalmopathy may result in blurred vision and ulcers of the cornea. 

In severe cases, Graves' opthalmopathy can cause swelling of the eye muscles that cause pressure on the optic nerve. This can result in vision loss or double vision.

Even though an overactive thyroid causes the disease, it's important to note that the hormones that are in control of the eyes are not the same as those that cause reactions in other parts of your body. There are cases in which people are diagnosed with Graves' opthalmopathy but do not have Graves' disease. This occurs in approximately 10 percent of cases.