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.
A: An impervious surface is a hard surface that does not let water soak into the ground or greatly reduces the amount of water that soaks into the ground. Examples include roofs, solid decks, patios, sidewalks, driveways, parking areas, and roads.Compacted gravel is considered an impervious surface.: Areas covered with grass or that are planted (such as forests or gardens) are not counted as impervious surface. For billing purposes, wooden decks (without roofs) and the area of swimming pools that actually hold water are considered pervious.