Minimum amount of light for low vision

• If 90 photons enter the eye ,10 or less are actually absorbed in photoreceptors.
• About 3% are reflected at the surface of the cornea, and about 50% are absorbed in the various structures(cornea, lens, and humors).
• Of these that reach the region of the rods ,only about 20% (~10%of the  original no.) are absorbed in the rods.
• The photons that miss the rods are absorbed in the “backstop”.

Note: Some animals ,such as cuts have a reflective coating behind the rods that give  the rods another opportunity to absorb the photons ,these animals have eyes that “glowing in the dark” if a light shines in them.