A 26 yrs old male with restriction of eye movements in all directions & moderate ptosis but with no diplopia or squint. Diagnosis is-

Chronic progressive external ophthalmoplegia is characterized by bilateral ptosis without diplopia in early adulthood. Ophthalmoplegia is symmetrical and slowly progressive, so diplopia is not often a complaint because all eye movements are reduced equally. Multiple cranial nerve palsies and mysthenia gravis present with diplopia along with ophthalmoplegia and other symptoms. Thyroid ophthalmopathy is associated with lid retraction (not ptosis).