This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Strabismus, Subject name: Ophthalmology
A 26 years old male with restriction of eye movements in all directions and moderate ptosis but with no Diplopia or squint. Diagnosis is 
Select and explain. 
A. Thyroid ophthalmopathy, B. Chronic progressive external ophthalmoplegia, C. Myasthenia gravis, D. Multiple cranial nerve palsies
B: Chronic progressive external ophthalmoplegia
Answer: B: Chronic progressive external ophthalmoplegia 
Explanation: Ans. (b) Chronic progressive external ophthalmoplegiaRef: Kanski 7/e, p. 852Restriction of ocular movement in both eyes are symmetrical in chronic progressive external ophthalmoplegia, so there is no diplopia.