The human eye is a paired sense organ that reacts to light and allows vision. Rod and cone cells in the retina are photoreceptive cells which are able to detect visible light and convey this information to the brain. Eyes signal information which is used by the brain to elicit the perception of color, shape, depth, movement, and other features. The eye is part of the sensory nervous system.
Similar to the eyes of other mammals, the human eye's non-image-forming photosensitive ganglion cells in the retina receive light signals which affect adjustment of the size of the pupil, regulation and suppression of the hormone melatonin, and entrainment of the circadian rhythm.
Considering that the eyes are wet and exposed all the time and one would think that in contact with cold winter temperatures they might freeze, eyeballs are actually always warm even though unprotected. Unlike other bodily extremities, the eyes are constantly pumped with a strong supply of warm blood—even in the coldest situations. Furthermore, our eyes are nestled rather deeply in our heads where bone, tissue, and fat also help keep them warm. Essentially, it’s virtually impossible for the eyes to freeze as long as they are inside a warm, functioning body.
The primary blood source to the eye is the ophthalmic artery, which is a branch of the same deep artery that supplies the brain. When in cold surroundings, the body diverts even more blood to the brain which, in turn, helps keep eyes even warmer.
Because tears are saltwater, they are also resistant to freezing; however, they can solidify in extreme cold and possibly “gum up” the eyelids. Even so, the eye itself will be unaffected. Basically, our eyes will only naturally freeze after our bodies are dead and cold. Saltwater freezes at much colder temperatures than normal water, which is why our eyes can stay moist in sub-zero temperatures with our salty tear drops.
Even though eyeballs do not get cold in winter, additional brightness from the snow can ‘burn’ your eyes. Too much UV exposure can cause inflammation of the cornea, a condition called keratitis, which makes your eyes red, sore and sensitive to light.
- 1/4 cup olive oil
- 4 cloves garlic, minced
- 1 teaspoon salt
- 4 pounds frozen chicken wings, thawed
- 1/4 cup (1/2 stick) butter, melted
- 1 tablespoon lemon juice
- 1 tablespoon lemon zest
- 1 tablespoon coarsely ground black pepper
And births this date include...