Eyeball, located in the orbit. Eyelid protection in the front, optic nerve connection in the back, and orbital fat pad around. The average diameter of normal adults is 24 mm, and the average vertical diameter is 23 mm. The front end protrudes from the orbit 12 ~ 14 mm and is covered by eyelids. The eyeball includes the wall of the eyeball, the inner cavity of the eye, contents, nerves, blood vessels and other tissues.
First of all, the eyeball wall
The ocular wall is mainly divided into outer layer, middle layer and inner layer.
The outer layer consists of cornea and sclera. The outer layer of heel ball plays a role in maintaining the shape of eyeball and protecting intraocular tissue. Cornea is the highest entrance to receive information. The cornea is the transparent part in front of the eyeball, through which light enters the eyeball. Cornea is not only the main structure of light entering eyes and refracting imaging, but also plays a protective role and is an important part of measuring people's perception. Scleral is a compact collagen fiber structure, opaque, milky and tough.
The middle layer, also known as grape membrane and pigment membrane, is rich in pigment and blood vessels. Include iris, ciliary body and choroid.
Iris: annular, at the forefront of the uvea, in front of the lens. People of different races have different iris colors. There is a -2.5 ~ 4 mm round hole in the center of iris, which is called pupil. It is the portal for external objects and light to enter the eyes. There are two kinds of smooth muscles in iris, one is called pupil sphincter, and the other is called dilating pupil muscle. Their main function is to adjust the amount of light entering the eyes. When the external light is too strong, the pupil shrinks; When the outside light is weak, the pupil will be dilated.
Ciliary body: anterior iris root, posterior choroid, sclera on the outside, lens equator on the inside through suspensory ligament. The ciliary body includes ciliary muscle, abundant blood vessels and trigeminal nerve endings, and is innervated by parasympathetic nerves. It secretes aqueous humor, which is related to intraocular pressure and tissue nutrition metabolism; The ciliary body also adjusts the diopter of the lens through the suspensory ligament, so that things far and near can be seen clearly.
The choroid lies between the sclera and retina. The choroidal contact circulation nourishes the outer layer of retina, which is rich in pigments to cover the darkroom. Only light is allowed to enter through the pupil.
The inner layer is the retina, a transparent film, which is the photosensitive system of the eyes and plays the role of feeling strong light and distinguishing the shape and color of objects. It is also the first stop of nerve information transmission formed by vision. It has a fine network structure and rich metabolic and physiological functions.
Second, the intraocular cavity and contents
The eye includes anterior chamber, posterior chamber and vitreous cavity. Ocular contents include aqueous humor, crystals and vitreous body. They are transparent and are called refractive media together with the cornea. Aqueous humor is colorless and transparent, produced by ciliary process, which nourishes cornea, lens and vitreous body, helps to bend light and maintain intraocular pressure. Crystal is an elastic transparent body, shaped like a biconvex lens, located behind the iris and pupil and in front of the vitreous body. Vitreous body is a transparent colloid, which fills the cavity behind 4/5 of eyeball. The main ingredient is water. Vitreous body has refractive effect and also supports retina.
Third, optic nerve, visual path
The optic nerve is a part of the central nervous system. The visual information obtained by retina is transmitted to the brain through optic nerve. Visual pathway refers to the whole nerve impulse transmission pathway from retina to visual cortex.
Fourth, eye accessories
Eye accessories include eyelid, conjunctiva, lacrimal apparatus, extraocular muscles and orbit. Eyelids are divided into upper eyelids and lower eyelids, which live in front of the orbit and cover the front of the eyeball. The gap between the upper and lower eyelids is called blepharoptosis. The joint of the two eyelids is called the inner canthus and the outer canthus respectively. The fleshy bulge in the inner canthus is called lacrimal caruncle. There is a perforated nipple on the inner side of the upper and lower eyelid margins, called lacrimal punctum, which is the opening of lacrimal canaliculus. The physiological function is mainly to protect the eyeball. Because of frequent blinking, tears can wet the eyeball surface, keep the cornea shiny, and clean the dust and bacteria in the conjunctival sac.
The process of seeing with the eyes is just like the process of taking pictures with a camera. Light enters the eyeball from the front of the eye, passes through the cornea, aqueous humor, pupil, lens and vitreous body, and reaches the retina. After complex biological photochemical reactions, biological currents are generated, which are transmitted to the brain through the optic nerve (like cables), and are perceived to form vision.
We know the structure and function of the eyes, and know that the eyes are the most important organs in human senses, and about 80% of the knowledge and memory in the brain are obtained through the eyes. Reading books, looking at pictures and appreciating paintings, appreciating people and enjoying beautiful scenery all need eyes. The eyes can distinguish different colors and different lights, and then transform these visions and images into nerve signals and transmit them to the brain. Because eyesight is so important to people, everyone should have their eyesight checked every year or two. Protect our eyes.
Health guide
What is color blindness?
Congenital color vision disorder is usually called color blindness, which can't distinguish various colors or a certain color in the natural spectrum. The poor ability to distinguish colors is called color weakness, and the boundary between it and color blindness is generally not easy to distinguish strictly, but the severity is different. Color blindness can be divided into color blindness and partial color blindness (red blindness, green blindness, blue-yellow blindness, etc. ). Color weakness includes full color weakness and partial color weakness (red weakness, green weakness, blue yellow weakness, etc. ).
Color-blind (weak) patients are born with no correct color discrimination ability, and think that others are the same as themselves, so they don't feel sick. Many color-blind patients have no abnormal findings in eye examination. When the red and green colors are particularly obvious or single, patients often distinguish them by unique experience, so color blindness (color weakness) can only be judged by special color vision examination. Color-blind people will be restricted by many majors in their work, so they should pay attention to those majors when applying for universities, so as to avoid them in advance.
Color blindness restriction major:
1. Minor color vision abnormality (commonly known as color weakness) can't be admitted: chemistry, chemical engineering and pharmacy, pharmacy, biological science, public security technology, geology and medicine with strict technical standards for color wavelength; Biological engineering, biomedical engineering, animal medicine, animal science, wildlife and nature reserve management, psychology, applied psychology, ecology, reconnaissance, special energy engineering and pyrotechnic technology, archaeology, marine science, marine technology, marine engineering, food science and engineering, light chemical industry, forest chemical industry, agronomy, horticulture, plant protection, tea science, forestry, horticulture, sericulture. Material chemistry, environmental engineering, polymer materials and engineering, process equipment and control engineering, preschool education, special education, physical education, sports training, sports human science, national traditional sports.
2. The majors that can't be admitted with abnormal color vision degree II (commonly known as color blindness) are fine arts, painting, art design, photography, animation, museum science, applied physics, astronomy, geographical science, applied meteorology, material physics, mineral processing engineering, resource exploration engineering, metallurgical engineering, inorganic nonmetallic material engineering, transportation, oil and gas storage and transportation engineering, etc. The specialty is the same as or similar to the above major.