Creating an eyeball with realistic texture

From layer menu select layer style>>create layers. Select and merge all the resulting layers.

Create a circular selection using elliptical marquee tool.

Press Shift+Ctrl+D to feather the selection. Press Shift+Ctrl+I to invert selection & press Delete.

Change the layer mode to "Overlay" and opacity to 40%.from the layer palette.

Similarly create another texture layer and reduce the opacity.

Create a circle using elliptical shape tool. Fill it with light black.

Create a small circle using elliptical shape tool. Fill it with Z Black color.