Eyeball

[Edit this paragraph] Eyeball (Bulbusoculi)[eyeball]

The eye of vertebrate animals is composed of sclera, cornea and their contents, generally speaking The main part of the ball-shaped eye

is located in the orbit, and the optic nerve is connected to the brain at the back end. The structure of the eyeball is divided into two parts: the eyeball wall and the content.

(1) The wall of the eyeball

is divided into three layers, namely the fibrous membrane, the vascular membrane and the retina from the outside to the inside.

1. Fibrous membrane: Thick and tough, composed of dense connective tissue, it is the shell of the eyeball. It can be divided into the cornea in front and the sclera in back.

Cornea: Occupying about 1/5 of the front part of the eyeball, it is a transparent refractive structure with a spherical surface that is convex on the outside and concave on the inside. It is thicker at the periphery and thinner in the middle, embedded in the sclera. The surface of the cornea is covered by the bulbar conjunctiva. The inner surface of the cornea and the iris form the anterior chamber of the eye, which contains aqueous humor.

Sclera: It occupies about 4/5 of the back of the eyeball. It is milky white and opaque. It is used to protect the internal structure of the eyeball. The sclera is connected to the cornea in front, and there is a ring-shaped scleral sinus at the junction, which is the channel for the aqueous fluid to flow out and plays a role in regulating intraocular pressure. On the posteroventral side of the sclera, where the optic nerve fibers pass through, there is a scleral cribriform plate.

2. Vascular membrane: It is the middle layer of the eyeball wall, located between the fibrous membrane and the retina. It is rich in blood vessels and pigment cells, nourishes the tissues in the eye, and creates a dark environment, which is beneficial to the retina. Sensitivity to light color. The vascular membrane is divided into 3 parts from back to front: choroid, ciliary body and iris.

Choroidea: brown in color, used to nourish the eyeball. Lining the inner surface of the sclera, the back wall has a greenish-green triangular area with metallic luster, called the tapetum. Since the retina in this area has no pigment, it is highly reflective, which helps the animal to operate in the dark. Sensing light in a light environment.

Ciliary body (Corpusciliare): It is the thickened part in the middle of the vascular membrane. It surrounds the lens in a ring shape to form a ciliary ring. Its surface has many wrinkles that protrude inward and are arranged radially. , called ciliary process. The ciliary process and the lens are connected by a thin lens ligament. The ciliary muscle is composed of smooth muscles outside the ciliary body. The muscle fibers originate from the junction of the cornea and the sclera and end posteriorly at the ciliary ring. The ciliary muscle is controlled by the parasympathetic nerve. When it contracts, it can pull the ciliary body forward, relax the lens ligament, and regulate vision.

Iris: It is the frontmost part of the vascular membrane and is ring-shaped. Located in front of the lens, it divides the eye chamber into the anterior chamber and the posterior chamber. The periphery of the iris is connected to the ciliary body, and there is a hole in the center to let light pass through, called the pupil. Pigment cells, blood vessels and muscles are distributed within the iris. There are two types of iris muscles: one is called the pupillary sphincter, which surrounds the edge of the pupil. Its contraction can narrow the pupil and is controlled by the parasympathetic nerve; the other is a radial muscle fiber called the pupillary dilator muscle, whose contraction can dilate the pupil. The pupils of pigs are round, while those of other domestic animals are oval. There are granular protrusions on the free edge of the horse's pupil, called iris granules (Granulairidis).

Eyeballs and eyeball diseases 3. Retina: It is the innermost layer of the eyeball wall. There are also many light-sensitive cells that can feel the stimulation of light. It can be divided into visual part and blind part.

Optic part: Lining the inner surface of the choroid, and closely connected with it, thin and soft. It is slightly light red when alive, becomes cloudy after death, turns gray-white, and is easy to fall off from the choroid. There is a optic papilla (Papilla optici) at the back of the retina, which is an oval white spot with a slightly concave surface. It is where the optic nerve fibers penetrate the retina and has no light-sensitive ability. It is also called a blind spot. The central retinal artery branches from this branch and distributes radially across the retina. The central area of ??the retina at the back end of the eyeball is the most sensitive part of the eye. It forms a circular area called the retinal center (Areacentralisretinae), which is equivalent to the macula luten (Maculaluten) of the human eye. The outer layer of the optic part of the retina is the pigment epithelial layer, and the inner layer is the neural layer. The neural layer is composed of level 3 neurons from shallow to deep. The most superficial layer is the photoreceptor cells, which have two types of cells, namely cones and rods. The former has the ability to sense strong light and distinguish colors; the latter has the ability to sense weak light. Level 2 neurons are bipolar neurons, which are interneurons. The third level is multipolar neurons, called ganglion cells, whose axons converge towards the retinal papilla and become the optic nerve.

The blind part of the retina has no photosensitive ability. The outer layer is pigment epithelium and the inner layer has no neurons. Covered on the inner surface of the ciliary body and iris.

(2). The contents of the eyeball

The contents of the eyeball are some colorless and transparent refractive structures in the eyeball, including the lens, aqueous humor and vitreous body, which together with the cornea form the eye. refractive system.

1. Lens (Lenscrystallina): Biconvex lens shape, transparent and elastic, located between the iris and vitreous body. The periphery is connected to the ciliary process by the lens ligament. Its essence is composed of multiple layers of fibers.

2. Aqueous humor and chamber: The chamber (Comeraoculi) is the space between the cornea and the lens, and is divided into the anterior chamber and the posterior chamber by the iris.

Aqueous humor (Humoraqueus) is a colorless and transparent liquid that fills the eye chamber. It is mainly secreted by the ciliary body and then penetrates into the scleral venous sinus around the periphery of the anterior chamber to reach the ophthalmic vein. Aqueous humor transports nutrients and metabolites, refracts light, and regulates intraocular pressure.

3. Vitreous body (Corpusvitreum): It is a colorless and transparent jelly-like substance, filled between the lens and the retina, and surrounded by a transparent vitreous membrane. In addition to refracting light, the vitreous also plays a role in supporting the retina.

4. The refractive device of the eye is composed of four parts: cornea, aqueous humor, lens and vitreous body. The most common features are colorless, transparent and allow light to pass through, so they are collectively called the refractive device of the eye. . Any part of the disease will affect vision and cause refractive errors, such as myopia or hyperopia.

[Edit this paragraph] Penetrating injuries to the eyeball

Caused by cuts or stab wounds from sharp or pointed objects, foreign body debris entering the eyeball, and injuries caused by blunt objects. Those that cause rupture of the eyeball are called perforating wounds of the eyeball. A double-penetration wound that penetrates the entire eyeball from the front and exits from the rear is called a penetration wound of the eyeball, which is a type of penetrating injury of the eyeball.

Diagnosis

The basis for diagnosis of penetrating eyeball injury is summarized as follows: ⑴ history of trauma; ⑵ eyeball wound; ⑶ decreased intraocular pressure; ⑷ shallowing of the anterior chamber; ⑸ iris perforation ; ⑹ Pupil deformation; ⑺ Lens opacity; ⑻ Vitreous trauma channel; ⑼ Retinal damage; ⑽ Retention of foreign bodies; ⑾ Decreased vision.

Some of the above items may not be obvious or appear, especially for small penetrating injuries, and even all symptoms may not be obvious. Therefore, for every patient suspected of having eye trauma, a detailed medical history must be obtained and a careful examination must be conducted to avoid missed diagnosis and delayed treatment.

Treatment measures

Penetrating eyeball injuries vary depending on the cause of the disease, the location of the injury, and the severity of the injury. Therefore, the treatment methods are also different. Penetrating eyeball injuries are mainly For surgical treatment, only the treatment principles and points of attention will be described.

1. Prevention of infection: When the eyeball is injured, the injuring object often brings pathogenic microorganisms directly into the eye, or infection occurs later because the wound remains open. Therefore, when dealing with penetrating eyeball injuries, we must first pay attention to preventing infection and stopping infection that has already occurred. The method is to firstly wipe the eyelids and surrounding skin after a preliminary understanding of the injured area and condition, and clean the eyes with saline swabs but do not rinse them. If there is any suspicion of contamination, clean it with 1:5000 liter mercury solution or mercury oxycyanide solution. After various examinations and proper wound closure, antibiotics are injected into the subconjunctiva, antibiotic eye drops are dripped into the conjunctival sac, and the wound is covered with gauze. If the wound is large and deep, and the wound is exposed for a long time, antibiotics need to be injected into the eyeball, a sufficient amount of antibiotics should be applied to the whole body, or traditional Chinese medicine heat-clearing and detoxifying agents should be added, and tetanus antitoxin or mimetics should be injected.

2. To seal the wound, the wound must be properly treated and tightly sealed to prevent secondary infection, prevent the eye contents from protruding, stop bleeding, restore intraocular pressure, and maintain the normal position of each tissue structure. The treatment methods are as follows:

⑴ Treatment of small wounds: In principle, wounds on the cornea and sclera should be tightly sutured, but if the wound is small and has not been opened without the contents of the eye being prolapsed or incarcerated, it can also be treated. No suturing is required. After treatment according to the above method, both eyes or one eye may be bandaged, or a protective goggle may be added and the patient may lie down quietly.

⑵ Corneal wounds must be sutured directly immediately. Under the operating microscope, use 10-0 or 9-0 sutures with a spade needle, and the depth should be more than 2/3 of the corneal thickness; for oblique wounds or long-term corneal edema, the depth should be 3/4. above, but it cannot penetrate the cornea. The number of sutures in the center of the cornea should be minimized and the sutures must be tight to maintain normal congruity. After suturing, balanced saline or sterile air is injected into the anterior chamber to prevent iris adhesion. If the corneal tissue is broken and cannot be sutured, corneal transplantation can be used to repair it. If this condition is not available, conjunctival flap can be used to cover it.

⑶Scleral wounds, regardless of whether the bulbar conjunctiva is ruptured or not, should be sutured promptly. Sometimes the scleral wound extends far back, or goes under the eye muscle. The back end of the wound must be found and sutured properly. If there is still bleeding on the surface of the sclera at the wound, it should be cauterized to stop the bleeding. The tissue containing blood vessels should be scraped off, and it should not be clamped in the scleral wound. For extremely small simple scleral wounds, if there is no wound on the bulbar conjunctiva or the wound has healed, it is not necessary. Stitch.

⑷ For larger wounds with prolapse of eye contents, the prolapsed uveal tissue should be removed if it is contaminated or necrotic. However, the prolapsed uvea is not contaminated or necrotic. Although it takes a little longer, it can be returned to the eye after being fully cleaned with antibiotics, and the wound can then be sutured. The uvea that has prolapsed under the bulbar conjunctiva is covered by the conjunctiva. As long as there is no obvious necrosis, it can be returned without resection. The vitreous body embedded in the wound should be removed and cut off repeatedly with a plastic sponge swab or cotton swab until there is no vitreous body in the wound. It is best to remove the vitreous body from the wound with a vitrectomy device. Intercalated broken crystals should be adequately removed.

⑸When a foreign body is seen in the wound, the foreign body should be removed first and then the wound should be treated.

⑹ If the wound is very large and the eyeball damage is extremely serious, whether the eyeball should be preserved can be considered in conjunction with the prevention of sympathetic ophthalmia.

3. Prevent bleeding: When the injury involves the uvea and retina, attention should be paid to preventing bleeding. Those who have been found to be bleeding should be treated more actively. It is common in clinical practice to see some cases in which the wounds on various parts of the eyeball have been properly treated and healed satisfactorily, but the vitreous opacity and organization caused by bleeding and hemorrhage have become the main reason for affecting vision and even causing blindness. To prevent bleeding, various hemostatic agents of Western medicine and traditional Chinese medicine can be used. The patient lies still, the injured or both eyes are bandaged, and the goggles should be deepened to avoid shock and pressure on the eyeballs. For those with heavy bleeding and slow absorption, vitrectomy is feasible.

4. Prevent inflammatory reaction: For severe penetrating injuries, especially those that damage the uvea, attention should be paid to preventing inflammatory reactions, using mydriasis, local and systemic application of corticosteroids, or oral administration of sodium salicylate. , non-steroidal anti-inflammatory agents such as aspirin or indomethacin, and heat-clearing and wind-clearing agents of traditional Chinese medicine.

5. Early vitrectomy. For severe penetrating eyeball injuries, vitrectomy can be performed when the wound is treated and closed for the first time, if necessary. Remove injured vitreous or vitreous hemorrhage, remove broken crystals, etc. It is relatively safe and reliable to enter the resector through the pars plana of the pars plana to remove the lens and vitreous body that accumulates blood or is damaged. And after the removal, the condition of the fundus can be checked for further treatment. The significance of early vitrectomy is also to prevent serious consequences such as retinal detachment caused by subsequent vitreous shrinkage. In addition, in the early stages of purulent endophthalmitis or panophthalmitis, vitrectomy combined with intraocular injection of antibiotics has a good therapeutic effect.

6. Treatment of penetrating eyeball injuries: Penetrating eyeball injuries, that is, double penetrating injuries or secondary perforating injuries of the eyeballs. While the front wound is being treated, the rear wound should be treated as well. If the posterior wound is smaller, if suturing is necessary, transvitreous diathermy can be performed to coagulate the retinal choroid around the wound. If the posterior wound is larger, or there is obvious retinal detachment, the scleral wound should be sutured. Transscleral diathermy or condensation or scleral folding and padding should be performed. Vitrectomy should be performed early in case of penetrating eyeball injury.

7. Treatment of explosion injuries: In addition to eye injuries, explosion injuries are often combined with trauma to other parts of the body. During treatment, attention should be paid to the treatment of trauma to the brain, internal organs, and limbs, and lives should be saved first. Explosion injuries are mostly to both eyes, with numerous wounds, or with the presence of numerous foreign bodies. Most of the debris from the explosion carries soil and dirt. Pay special attention to preventing infection during treatment. Depending on the location and extent of the injury, refer to the aforementioned methods for treatment.

8. Treatment of traumatic cataract and lens dislocation: see lens disease.

9. Treatment of purulent endophthalmitis and ophthalmitis: see vitreous disease, exogenous endophthalmitis and panuveitis, and endogenous endophthalmitis.

10. Prevention and treatment of sympathetic ophthalmia: see uveitis.