Did you know?  The average person has almost no idea how the eye works! When educating patients about their eye conditions, I routinely start from square one, and give them a quick overview of how the eye works. The simplest and most accurate explanation is that the eye is like a camera.Light enters the camera through its lens, is inverted, and lands on the film (or digital sensor), where it can be processed into a picture.

Similarly, light enter the eye through the cornea (the clear window) and passes through the lens, where it is inverted. The light then lands on the retina, which is like the film in the camera. The signals from the retina travel through the optic nerve to the brain, where they are processed into a picture.

 

(image courtesy of the American Academy of Ophthalmology, with permission)

Did you also know? The pupil of the eye is like the aperture of the lens. In dim light, a photographer opens the aperture wider, letting more light in. Similarly, the pupil enlarges in dim light, letting more light in. In dim light, the photographer will choose a more sensitive film (or increase the sensitivity of the sensor). Similarly, the retina gradually adapts to dim light by becoming more sensitive to light (think of walking into a dim movie theater.) 

So, are your eyes Nikon or Canon?