Ans. a (Blow out fracture of the floor of the orbit) (Ref. Grainger Diagnostic Rad 4th/2527; Ref . Q. 159. Of MH-2207)BLOW-OUT FRACTURE is caused by fracturing of the orbital walls with herniation of orbital contents and subsequent tethering of the globe, resulting in pain and diplopia. It usually involves the orbital floor with 'trap-door deformity' on skull AP view or characteristic "Tear drop" sign on X-ray PNS.Also Know:# Tripod Fracture: zygomaticomaxillary fracture# "pyramidal" fracture = Le Fort II fracture (fracture medial orbital and lateral maxillary walls).# Bare orbit sign: Neurofibromatosis# Coke-bottle sign: thyroid ophthalmopathy# "Mushroom-shaped" posterior segment mass: choroidal melanoma# Calcification is pathognomonic of: Retinoblastoma# Most common intraorbital tumor in adults: Cavernous hemangioma.