Think film used in a camera.
The retina from Latin rēte, meaning “net”) is the third and inner coat of the eye which is a light-sensitive layer of tissue. The optics of the eye create an image of the visual world on the retina (through the cornea and lens), which serves much the same function as the film in a camera. When light strikes the retina it initiates a cascading chemical like affect of electrical events where then it triggers nerve impulses. These impulses are then sent to various visual receptors of the brain through the optic nerve fibers.
We did say we were getting Scientific didn’t we?
Breaking it down or dissecting if you will; the retina is a structured tangled mess (to us) of layered neurons. These neurons are then interconnected by synapses (do we explain synapses? Not just yet). Now, the photoreceptor cells are the ONLY neurons that are light sensitive. Breaking it down some more, there are mainly two type of photoreceptor cells; Rods and Cones. Rods mainly function in dim light and provide black-and-white vision (wonder why it’s hard to see color in dim light?). Cones are the other-hand (figure of speech) support daytime vision and…….you guessed it; color perception.
Now a third, equally as important and far more rare type of photoreceptor, is the ganglion cell. it’s function is to provide a reflexive response to bright light…mainly sunlight. Ever wonder why you need those sunglasses because your eyes hurt? Well, its that little ganglion cell photoreceptor. The longer you wear those sunglasses the least time that little cell has a chance to condition itself. ( in theory really)
We only have scratched the surface here – (again, figure of speech, not the actual retina) but it’s a general idea.