The posterior portion of the vascular tunic, associated with the sclera, is the .

The posterior portion of the vascular tunic associated with the sclera is known as the choroid.

The vascular tunic, also referred to as the uvea, is the middle layer of the eye wall and consists of three parts: the iris, the ciliary body, and the choroid. The choroid plays a crucial role in providing nourishment to the outer layers of the retina through its extensive network of blood vessels. In addition to its vascular functions, the choroid is also significant for its dark pigment, which helps to absorb excess light and prevents scattering within the eye. This light absorption helps ensure that visual signals are detected more clearly by the photo-receptive cells in the retina. The intricate relationship between the choroid and the retinal structure underlines its importance in maintaining optimal visual function.