First sign of optic nerve disease is:
Papilloedema
Colour blindness
Afferent pupillary defect
Efferent pupillary defect
C i.e. Afferent pupillary defect Marcuss Gunn pupil or RAPD (relative afferent papillary defect) is the earliest indication of optic nerve disease even in presence of normal visual acuity.Q