Enlarged Pupils Are Usually A Normal Occurrence
Enlarged pupils are a common occurrence as we go about our daily, and nightly, activities. The function of the pupil, the round area in the center of the eye, is to allow light into the eye and to strike the retina. The larger the pupil is, the more light will enter the eye. An enlarged pupil is normally a response of the eye to a lessening of available light. An enlarged pupil will let more light enter, making vision easier or better.
The Role Of The Iris - The size of the pupil is controlled by the action of the iris. The iris is a circular muscle, several muscles actually, surrounding the pupil. When the muscles contract, the pupil becomes smaller, when they expand, the pupil becomes larger. The muscles of the iris are controlled by the nervous system. Abnormally enlarged pupils, that is enlarged pupils that have become that way for some reason other than stimulus by any absence of light, are almost always caused by something affecting the nervous system. Abnormally enlarged pupils tend to remain in that state for some time, indicating that something is wrong.
Our eyes dilate when we enter a darkened room. Since the muscles in the iris cannot expand instantly, we don't receive much light on the retina at first and have trouble seeing in the dark. If we go from a darkened room into a brightly lighted room, the light will seem too strong, as the muscles in the iris cannot contract instantly. We may have trouble seeing at first, for a different reason. The eyes quickly adjust however, making vision normal again.
An abnormal situation can occur with some types of illness, or an eye disease, in which the iris expands and the pupils are constantly dilated, in other words abnormally enlarged. There are quite a number of causes of enlarged pupils, where the pupils not only enlarge, but tend to remain that way, irrespective of the intensity of the light that is entering the eye. As one might expect, most all of these causes affect the nervous system, which then cannot function normally with respect to controlling the muscles in the iris.
Poisons And Toxins - Among the more common causes of enlarged pupils are drugs, medications, toxic agents, and poisoning. There are a wide variety of poisonous plants and herbs which, when ingested, will result in enlarged pupils as one of the symptoms of poisoning. In fact, it's not just eating poisonous plants, but almost any kind of food poisoning that will affect the nervous system and the control of the muscles in the iris. What is happening is that when the iris expands, it is relaxing, and the effect of the poison or toxic agent on the nervous system is one of keeping these muscles relaxed.
When We Dilate The Eyes On Purpose - We experience this when we go in for an eye exam. The ophthalmologist will put drops of what are referred to as mydriatics on our eye. This medication forces the eye to dilate by not allowing the iris to contract, but rather relaxing the muscles of the iris so that the pupil is enlarged. This condition is temporary but may last for up to an hour, forcing you to wear dark glasses, usually provided, to avoid eye damage when you step outside into the bright sunlight.
Other Causes - Besides poisons, many narcotic and hallucinatory drugs will affect the nervous system and cause the pupils to dilate. So will an adverse reaction to or an overdose of certain herbs. A person suffering from a concussion often will exhibit enlarged pupils, as will someone who has suffered a heart attack, or is experiencing a grand mal seizure.
Enlarged pupils are therefore usually an indication of something gone wrong, but not with the eyes. Enlarged pupils are in themselves not particularly dangerous unless too much light enters the eye over too long a period, such that there is a possibility of eye damage. If you see someone who has larger pupils than seem normal, it would be a good idea to seek out the cause, which could turn out to be something requiring attention.
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