Green’s Dictionary of Slang

1. (Aus.) a man who ogles (usu.) women.

1967		‘Whisper All Aussie Dict.’ in Kings Cross Whisper (Sydney) xxxviii 10/1: optic: A pervert, from optic nerve, perve.
1983		R. Aven-Bray Ridgey-Didge Oz Jack Lang 37: Optic Nerve Perve.
1996		Tracks (Aus.) June 43: [caption] Some things are the same at surf contests the world over: the chicks do aerobics [...] And the blokes go the big optic nerve.
1999		G. Seal Lingo 91: An optic nerve is a perv (pervert, as in one who perv[e]s at or ogles the opposite sex), often spoken as in cop an optic at that, being an enthusiastic comment on the attractiveness of – usually – a woman.

2. (N.Z. prison) an observation, a look around.

2001

D. Looser Boobslang [U. Canterbury D.Phil. thesis] 131/2: optic nerve n. a look around: ‘Get out there and have an optic nerve.