Nearly every morning you wake up and have to wipe the sleep from your eyes, sometimes literally. Although the weird crusty substance has many names, it is not really the result of the sandman's careless aim or any other mythical concoctions, it is just a sign that your body is doing precisely what it is supposed to be doing while you are sleeping.
Vocabulary
The sleep in your eyes is referred to by many different names. Sleep, eye crust and eye boogers are among the most popular. However, there is a scientific name for the crusty substance that collects in your eyes as you sleep. Rheum is the watery substance that is discharged through the nose, mouth or eyes, but the rheum found specifically in the eye is referred to as gound.
Eye Anatomy
According to Henry Newell Martin, author of "The Human Body," the parts of the eye involved in the production and movement of rheum are part of the conjuctiva and the lachrymal apparatus. If you look carefully at the small, reddish pink section of the eye closest to the nose, you will notice that there are actually two parts to it: a soft, bulging section and a smooth crescent moon-shaped piece. The softer, bulging section is called the caruncula lachrymalis, and it is the gland that excretes tears. The plica semilunaris or semilunar fold is the small, pink, moon-shaped organ located in the inner corner of the eye. The conjunctiva is another name for the cornea, which secretes a watery mucus substance called mucin. All together these secretions form the collective substance called rheum.
Particle Collection
During waking hours, the moisture in the eye collects foreign objects, like dust and dirt, and the motion of blinking washes them out of the eye to prevent any damage to the cornea. However, during sleep, the blinking motion is not available, so the pica semiluminaris picks up the slack by guiding the unwanted substances to the corner of the eye, where it will collect and dry during the night. It is this dried rheum that then becomes the crusty sleep in the morning.
Vestigial Organ
The pica semiluminaris was traditionally thought to be a vestigial organ, which is an organ that is left over from evolution and has no real modern function. Most pioneering anatomists believed it was a remnant of the third eyelid commonly found in birds and amphibians, but modern medicine has discovered that it actually has this very important purpose.
Removal Methods
Rheum, by design, tends to be a bit sticky, so the sleep left in your eyes overnight can sometimes be difficult to remove. This is especially true if you are caring for a young child who may not have the dexterity to remove it himself. You can remove the sleep in your eyes easiest in the shower since the warm, steamy environment will loosen up the substance, allowing it to be washed away easily. If you hit the snooze button too many times and need to skip the morning shower, it is best to use a soft cotton ball or cotton swab to remove the sleep from your eyes since your fingertips can have irritating oils or dirt on them that can be pushed into the eye along with the waste products already present in the dried gound.
References
- "The Human Body"; Henry Newell Martin; 2009
- "Anatomy, Descriptive and Surgical"; Henry Gray and Timothy Holmes; 1864
