**2. Arterial blood supply of the anterior part of the optic nerve**

Arterial blood supply of the anterior part of the ONH is presented in figure 1.

**Figure 1.** Arterial blood supply of the anterior part of the optic nerve.

The ONH consists of, from front to back: a). surface nerve fiber layer, b). prelaminar region, c). lamina cribrosa region, and d). retrolaminar region.

