This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Lacrimal Apparatus and Eyelid Disorders, Subject name: Ophthalmology
In which type of ptosis the amount of ptosis decreases with mouth opening 
Select and explain. 
A. Blepharophimosis syndrome, B. Marcus gunn ptosis, C. Myogenic ptosis, D. Neurogenic ptosis
B: Marcus gunn ptosis
Answer: B: Marcus gunn ptosis 
Explanation: Marcus Gunn Jaw Ptosis (congenital synkinetic ptosis) In this condition there occurs retraction of the ptotic lid with jaw movements, because with stimulation of ipsilateral pterygoid muscle the levator palpebrae is also stimulated due to trigemino occulomotor synkinesis In the picture look that on opening of the jaw, ptosis has improved, this is typically marcus jaw winking phenomenon.