What is the normal value of pupil

I wonder how much you know about normal pupil values? As the saying goes, eyes are the windows to the human soul. Without eyes, human survival will become difficult. Therefore, we should have some understanding and knowledge about our eyes. This time we will explain to you the composition of the pupil, hoping it will be of some use.

The pupil is the opening in the middle of the iris, which is the gateway for light to enter the eye.

The iris in the eye is disc-shaped with a small round hole in the middle, which is what we call the pupil, also called the "pupil". The normal value is 2.5--5mm (2--5mm). It shrinks in bright light and expands in dim light. There are two tiny muscles in the iris. One is called the sphincter pupillae, which surrounds the pupil and is less than 1 mm wide. It is responsible for the constriction of the pupil and is controlled by the parasympathetic nerves in the oculomotor nerve. The other is called the dilator pupillae, which is arranged radially in the iris and is responsible for the dilation of the pupil and is controlled by the sympathetic nerves. These two muscles coordinate and restrict each other, expanding and contracting to adapt to various different environments.

The iris is composed of multiple units of smooth muscle; the circular muscle layer around the pupil is innervated by the parasympathetic nerve fibers in the oculomotor nerve. When it contracts, it shrinks the pupil, so it is also called the pupillary sphincter; the peripheral part of the iris is the divergent muscle fibers, which are innervated by the sympathetic nerve fibers ascending from the neck. When it contracts, it dilates the pupil, so it is also called the pupillary dilator. The sphincter pupillae and dilator pupillae are the very few muscles in the human body that are differentiated from the neuroectoderm.

The size of the pupil controls the amount of light that enters the eye. The diameter of the pupil of an average person can vary between 1.5-8.0 mm. Assuming that the diameter of a person's pupil can increase 5 times when he enters a dark room from a bright place, then the light-receiving area of ​​the pupil should increase 25 times. It can be seen that the change of the pupil has the effect of keeping the amount of light entering the eye relatively constant under different lighting conditions. However, the intensity of light from strong sunlight in a dark room is actually weakened by about 1 million times, so changes in pupil size alone are far from enough to keep the amount of light entering the eye constant. In fact, the human eye receives light stimulation through different photoreceptor cells in the retina under different brightness conditions. The rod cells that work in dim light are much more sensitive to light than the cone cells that work in bright light. Therefore, to see objects in the dark, you only need to increase the amount of light entering the eye appropriately.

Did you expect that the pupil could be so complicated? In fact, every organ in the human body plays a very important role, especially our eyes. We communicate with the outside world through our eyes. It is because of our eyes that our lives become colorful. So, we should take care of our eyes. What do you think?