A patient presented with unilateral intermittent proptosis which was compressible and increases on bending forward. No thrill or bruit was present. MRI shows a retro orbital mass with enhancement. The likely diagnosis is:

Orbital venous anomalies (varices) produce intermittent proptosis, sometimes associated with pain and transient reduction of vision. Some degree of proptosis can be induced with Valsalva's maneuver or by placing the head in a dependent position. There may be acute exacerbations due to hemorrhage. MRI scan is usually diagnostic. Endovascular embolization is the preferred method of treatment. Surgery is very difficult, with risk of permanent impairment of vision. Ref: Sullivan J.H. (2011). Chapter 13. Orbit. In Riordan-Eva P, Cunningham E.T., Jr(Eds), Vaughan & Asbury's General Ophthalmology, 18e.