"He [Perseus] crept up on tiptoe,
keeping his footfall noiseless,
and with hollowed hand and
caught the roving eye..."
Nonnus, Dionysiaca 24. 270 ff
"He [Perseus] laid ambush for
the sentinel eye of Phorkys (Phorcys),
the ball of the sleepless eye
that passed from hand to hand,
giving each her share
under the wing of sleep in turn."
Nonnus, Dionysiaca 25. 64 ff
(trans. Rouse) (Greek epic C5th A.D.)