<prompt> Most common cause of unilateral proptosis is -ThyrotoxicosisRetinoblastomaIntraocular haemorrhageRaised intracranial tension  <response>: Most common cause of bilateral proptosis: In children : Neuroblastoma and leukemia chloroma. In adults : Thyroid ophthalmopathy. Most common cause of unilateral proptosis: In children : Orbital cellulitis. In adults : Thyroid ophthalmopathy. Ref: A. K. Khurana 6thE pg404 