Which of the following describes a healthy optic disk?

A healthy optic disk is characterized by being non-swollen and having clear, well-defined borders. This indicative appearance suggests that there is no underlying pathology affecting the optic nerve head, such as swelling caused by increased intracranial pressure or other diseases. A clear delineation of the optic disk is essential as it signifies healthy blood flow and the absence of edema or damage to the optic nerve.

The other descriptions, such as swollen and pale, large and blurry, or irregular with color changes, indicate various forms of optic nerve damage or pathological changes. Swelling can suggest conditions like papilledema, while blurriness and irregularity may indicate neuropathy or optic nerve disease. Thus, the clarity and definition of the borders of the optic disk serve as critical indicators of overall ocular health and the condition of the optic nerve.