If the receptors were at the front of the retina, the pigment cells would have to be between them and the next layer of nerve cells, in a region already packed with axons, dendrites, and synapses. As it is, the layers in front of the receptors are fairly transparent and probably do not blur the image much.
The definition of impervious is not being able to be penetrated or not able to be hurt. 1  An example of impervious is a fabric that does not allow any liquid to pass through. 2  An example of impervious is a figurine made out of indestructible material.
She is an object of popular fascination and clinical anguish: adult psychopathy is largely impervious to treatment, though programs are in place to treat callous, unemotional youth in hopes of preventing them from maturing into psychopaths.