Then formed him and breathed His Spirit into him and gave you hearing, sight and hearts. What little thanks you show! (As-Sajda, 9)
The eyes are one of the windows of the body, opening to the exterior world. The protection and maintenance of these vital organs are provided by the eyelids, which have a perfect creation. The duty of the eyelids is to protect the eyeball, as well as to maintain the “conjunctiva” and “cornea” at a certain moisture level. The blood vessels of the thin layer called the conjunctiva, on the inner part of the eyelids, feed the exterior layer of the eye that cannot receive oxygen during sleep.
The skin of the eyelid, which completely and firmly covers the eye socket when required, is relatively thin. The lower layer of the eyelid skin is lean and very loose. The blood is easily collected there. If the eyelid had thicker skin and a more bulky structure, then opening and closing the eyes would be much harder.
Everyone blinks thousands of times a day unknowingly. This movement is made involuntarily and the eyes are protected from intense light and airborne foreign bodies. This automatic action is a blessing which many people do not appreciate.
What would happen if this cleaning was not performed automatically? In such a case, one would only remember to blink when one felt irritation in his eyes. This would cause the eye to be contaminated with germs. As the eyes would not be cleaned completely, a misty, cloudy vision would occur. Blinking would become a major problem and people would need to concentrate on blinking throughout the day.
Antiseptic Eye Liquids
When the eyes blink, the eyelids water the eyes and clear the dirt, like windscreen wipers. As the eyelids are closed during sleep, the eyes are automatically protected against drying.
The eyelid is perfectly fitted to the curved structure of the eye. With this perfect harmony, every point on the front surface of the eye is contacted and cleansed during the opening and closing of the eyelid. If the eyelid did not perfectly cover the eye, then it would not be possible to clean the foreign substances completely.
An oily secretion, secreted during the opening and closing of the eyelids from special glands (meibomian glands) within the eyelids, prevents the lids from sticking to each other and facilitates the sliding of the eyelids over the eyes. (Harun Yahya, The Miracle in the Eye)
It is very important that the eyelid remains closed while sleeping. If the eyelid was open while sleeping, then sleeping would become an extremely difficult task. People would need dark rooms for sleeping and no one would be able to sleep during the daytime. Eyes which remained open during sleep would be vulnerable to all kinds of external irritant.
Early Warning System
The eye is protected against hazards by an existing early warning system. The fundamental elements of this system are the nerves located on or around the eye, which enable the eye to sense and assess any threat to the eyes. These nerves then stimulate the muscles operating the eyelid.
There are different types of muscles responsible for the opening and closing of the eyelids. The movement of the eyelids, dependant on these muscles, occurs in three ways:
- Regular blinking,
- Reflex closure,
- Voluntary closure.
Blinking according to the conditions:
Blinking is a characteristic of vertebrates living in an air environment and possessing eyelids. The eyelids close 10-20 times a minute involuntarily. Factors such as continuous reading, focusing, or the increase of moisture in the air, reduce the number of blinks. Factors such as the increase in temperature or light increase the blink rate. In this way, the cleansing of the eye is achieved automatically, without interruption, and with no inconvenience to the organism or human.
Reflexes are the involuntary reactions made within a short period of time against various external stimuli. This reflex mechanism activates the eyelid when required and protects against hazards. Touching the cornea or eyelash, or rapidly touching the center of the eyebrow or forehead causes a reflex, stimulating the eyelid to blink.
When the nerve network causing the blinking reflex is examined, it is clearly seen that this network has a finely planned structure. The warnings transmitted to the eyelid for each reflex mentioned above pass through different nerve paths. In other words, the eye is protected by several well equipped, early warning systems.
The brain evaluates these nervous warnings within a very short period of time and transmits the signals to the relevant muscles. During this event, the nerve signals do not lose their way, and they reach the brain in one thousandth of the second. As a result of the order received from the brain, the eyelid closes in a timely manner, in order to protect the eye from foreign substances, and to act as a windscreen wiper. The recognition of the existing hazard, and the transmission of reflex nerve signals without ever being lost or misinterpreted are indeed very complex events. The human being must be continuously informed about all external events that might affect him, in order to continue his life surrounded by constantly changing conditions. Therefore, blinking occurs very rapidly, so as not to affect the perception of the human being related to the exterior world. If this had taken longer, then people would miss significant dangers while in the act of blinking, which would severely affect life. The eyes, a few characteristics of which we have discussed here, are one of the greatest blessings that enable us to appreciate the outstanding artistry of Allah, and to be continuously grateful to Him for every moment that passes.