N - no signs or symptoms
O - only signs such as upper lid retraction; Kocher's sign
S - soft tissue involvement such as lid edema, lagophthalmos, conj chemosis
P - proptosis - exophthalmometry measures amount of proptosis; normal range is 12-12mm (whites), 12-24mm (blacks), 12-18 (asians).
E - EOM involvement. Results in diplopia; inferior rectus is typically affected first, followed by the medial, superior, and lateral recti.
C - corneal involvement.
S - sight loss (likely due to optic nerve compression. swollen EOMs at the orbital apex can compress the optic nerve (causing disc edema, APD, reduced color vision, visual field loss).