“…These gases have been described as persisting for approximately 6 weeks following surgery [3, 4]. If N 2 O is then administered as part of a general anaesthetic, N 2 O will diffuse into any persisting gas bubble and cause it to expand, and IOP pressure may increase sufficiently to cause retinal or optic nerve ischaemia [3]. Permanent visual loss may result, representing a disastrous and wholly avoidable complication.…”