The eye has three main layers. The cornea is the most powerful refractive surface, but the lens has a variable power that allows images from near objects to be focused on the retina.
Depth of field is adjusted by the iris.
The retina has 10 layers. The photoreceptor layer absorbs light. Photoreceptors synapse on retinal interneurons, which in turn synapse on each other and on ganglion cells. The latter project to the brain via the optic nerve through the optic disk. The fovea is specialized for high resolution and color vision and contains only cones.