I also agree about the myth part. In a healthy human looking at the structure of the eye (excluding the optic nerve) I can think of two factors that affect night vision capabilities:

the ratio of cone to rod cells (rod cells make you see at night). Both of which are part of the retina.

The effectiveness of the rod cells to "absorb" the light and stimulate the bipolar cells.

Other smaller factors that might be included is the distance between the rod cells and the fovea (centre of the retina where the light is focused on) and the ability of the iris to dilate, letting through more light.

Reinhardt