Diane DuCarlo, age 11, of Coventry, Rhode Island, for her question:
Why do our eyes blink?
Our precious eyes have several built in safety features and the blinking operation is an automatic program related to hygeine cleanliness. The eyeballs are recessed in protective bony sockets of the skull. Their front windows are shielded somewhat by the hairy lashes that sift a few dust particles before they enter the eyes. However, a lot of dusty debris does reach the surface of the eyes. Most of this material is removed by the blinking operation, acting like busy windshield wipers.
The air, as we well know, teems with microscopic particles of dusty debris and smoky smog. When all is calm, in a few hours this material deposits a layer of dust on surfaces indoors and outdoors. Invisible deposits also accumulate on our bodies as we move through the air. lie wash it from our skins and launder it from our clothes with little or no trouble. But the shiny surface of our eyes presents a more serious problem. These areas require constant wiping to keep the vision clear and also to protect the delicate membranes that cover the surface of the eyeballs.
This is why we blink our eyelids automatically every few seconds. The cunning operation is connected to its oum inside plumbing system and does more than a mere wiping job. The eyeball surface is a special membrane that requires a film of moisture. This teary liquid is the lachrimal fluid, a slightly salty blend of various soothing ingredients. It is manufactured in two spongy lachrimal glands, shaped like almonds and situated one at the outside corner of each eye, under the upper eyelid.
As the eyelids blink shut and open, the muscles involved squeeze a small helping of lachrimal fluid from the glands into the eyes. The same eyelid motion also wipes the moist, soothing fluid over the eyes, removing microscopic surface particles. The accumulation of fluid gently streams to the inside corners of the eyes. There at the corner of each lower lid is a small puncture called the lachrimal duct. Normally, the surplus fluid drains through these ducts into tubes that lead down in back of the nose. In times of tearful misery and uproarous laughter, the blinking muscles squeeze out extra lachrimal fluid. The flow is too much to drain down the normal channels ¬and rivers of tears stream down the cheeks.
Aside from cleaning, moistening and soothing the eye surface, the blinking operation keeps an emergency tactic in ever ready reserve. When something unexpected brushes close to the face, the eyelids blink shut to protect the precious eyes. They blink automatically before our conscious minds have time to evaluate the situation.
Sometimes a gritty speck gets through these marvelous defenses. The eyelids react to the painful intrusion with faster blinks .and streams of extra lachrimal fluid to float out the foreign body. If this fails, please resist the temptation to prod and poke. This is when a person needs either a gentle friend or an eye expert to perform some very delicate first aid. Later, the painful eye may be rinsed with clean water or a medicated lotion. But the sooner it gets back to bathing with its own superior built in lachrimal lotion, the better.