optic nerve morphology trait ocular fundus morphology trait optic disc morphology trait Any measurable or observable characteristic related to the shape, structure, color or pattern of the area in the retina where all of the axons of the ganglion cells exit the retina to form the optic nerve. Trait.ontology VT:0006215 EFO:0006939 EFO:0006937 EFO:0006936