If the patient feels that he/she can see normally with one eye after covering one eye, but sees things in double vision with both eyes, it may be due to a lesion in the nerve or blood vessels that govern the eye muscles, causing paralysis of the extraocular muscles and resulting in double vision in both eyes. Many patients with systemic diseases such as hypertension, diabetes and hyperthyroidism may develop extraocular muscle paralysis and prompt medical examination and treatment is recommended.