Abstract: Donating corneas means donating after death, but the relevant procedures should be done well before death. Donors must be voluntary during their lifetime, or with the consent of their families after their death, with the principle of respecting voluntariness. It is best to be 5 to 60 years old, but it can be relaxed to 7 years old. If used in medical research, it is not limited by age and disease. Donating corneas or eyeballs is free. Nowadays, voluntary donations are everywhere in the world. cornea

brief introduction

Donors must be voluntary before death or with the consent of their families after death. [ 1]? [2]? Respect for voluntariness is a principle. It is best to be 5 to 60 years old, or it can be relaxed to 70 years old. If used in medical research, it is not limited by age and disease. Corneal removal is restricted by many conditions, such as death certificate, infectious disease and time of death. , depending on environmental factors. Generally within 6 hours after death, and within 12 hours in winter. Donating corneas or eyeballs is free. Nowadays, voluntary donations are everywhere in the world. cornea

Description of donation

Donating an eyeball or cornea is a donation after death. But you have to go through the formalities before you die. Voluntary donors can go to the local provincial eye bank (located in Zhongshan Eye Center, No.54 Xianlie South Road, Guangzhou) to get the registration form. You need to clearly fill in "voluntary" and the signature of your family on the registration form. One copy of this form is kept by the volunteers and the other by the hospital. Registration forms can also be obtained by mail.

Brief introduction of cornea

There are abundant sensory nerves in the cornea, which mainly reach the cornea from the ophthalmic branch of trigeminal nerve through ciliary nerve. If the eyes are compared to a camera, the cornea is the lens of the camera, and eyelids and tears are the devices to protect the "lens". When we are unconscious, our eyelids blink. Every time we blink, tears will cover the corneal surface with a thin tear film to protect the "lens". Because the cornea is transparent, there are no blood vessels on it. Therefore, the cornea mainly gets nutrition from tears. If the nutrients contained in tears are insufficient, the cornea will become dry and the transparency will decrease. Cornea also gets oxygen from the air, so many people will feel a little dry after waking up. The composition of tears is very similar to the liquid part of blood, and oily components such as cholesterol and lecithin adhere to the corneal surface to inhibit water evaporation; Among them, the enzyme called lysozyme has bactericidal effect and can protect corneal infection bacteria that come into contact with the outside air.

The cornea is completely transparent, accounting for about 65,438+0/6 of the fibrous membrane. Seen from the back, the cornea is a perfect circle, and seen from the front, it is a transverse ellipse. The average transverse diameter of adult male cornea is 1 1.04mm, that of female cornea is 10.05mm, that of male cornea is 10. 13mm, and that of female cornea is10.08 mm. The central pupil area is approximately spherical in a circular area with a diameter of about 4mm, and the radii of curvature of each point are basically equal, while the cornea in the central area and the outer edge of the central area is flat, and the radii of curvature of each point are not equal. Measured from the front of cornea, the radius of curvature is 7.8mm in horizontal direction, 7.7mm in vertical direction and 6.22-6.8mm in posterior surface. Corneal thickness varies from place to place, with the central part being the thinnest, with an average of 0.5 mm, and the peripheral part being about 65438 0 mm. ..

The cornea is divided into five layers, from front to back: epithelial layer, anterior elastic layer (Bowman membrane), stromal layer (stroma), posterior elastic layer (posterior elastic layer) and endodermis. Epithelial cells are about 50um thick, accounting for 65438 00% of the total corneal thickness, and consist of 5-6 layers of cells. The epithelium around the cornea thickened and the number of cells increased to 8- 10 layer. In the past, it was thought that the front elastic layer was a special membrane, and it was found by electron microscope that the membrane was mainly composed of collagen fibers. The stroma layer is composed of collagen fibers, and its thickness is about 500um, accounting for 90% of the total corneal thickness. The parenchyma layer * * * contains 200-250 lamellae, which overlap each other. The lamellae are parallel to the corneal surface, and the lamellae are also parallel to each other, thus ensuring the transparency of the cornea. The posterior elastic layer is the basement membrane of corneal endothelial cells, which is easily separated from the adjacent matrix layer and endothelial cells. The back elastic layer is firm and has strong resistance to chemical substances and pathological injuries. Endothelial cells are monolayer cells, which are composed of about 500,000 hexagonal cells. The cell is 5 microns high and 65,438+08-20 microns wide. The nucleus is located in the center of the cell, oval in shape and about 7 microns in diameter.

corneal transplantation

Corneal transplantation is suitable for corneal opacity or edema caused by various reasons, which seriously affects vision: for example, corneal opacity caused by recurrent viral keratitis, patients who have not recurred within six months after thorough cure can consider corneal transplantation; Patients with corneal opacity burned by acid and alkali chemicals can undergo corneal transplantation one year after the injury is healed. Corneal ulcer with large range, deep invasion and long-term incurable, who has perforation or risk of invasion to the center after drug treatment failure, should be transplanted immediately; Patients with congenital corneal degeneration, keratoconus, corneal stroma degeneration and corneal endothelial cell dysfunction should also undergo corneal transplantation immediately; Corneal transplantation can be considered for patients with corneal tumor, corneal fistula and corneal staphyloma. Patients with corneal leukoplakia blindness can also consider corneal transplantation to improve their appearance.

Corneal transplantation materials can be divided into living donation and corpse donation according to their sources. The so-called living donor, as the name implies, is a living person, and the cornea is a complete eyeball because of trauma, optic nerve diseases, intracranial diseases and other reasons, so it is a suitable donor. The Eye Center of Zhejiang People's Hospital successfully completed two cases of living cornea transplantation in March and February, 2006, and one of them was the first living donor cornea for the blind in China. But at present, the vast majority of corneal transplantation materials in China still come from fresh corpses (donors). Generally, it is suitable for people with healthy corneas from 6 to 60 years old, especially those who died of acute diseases or trauma, and it is best to be between 18-35 years old. Babies within six months and elderly people over 90 years old are not suitable for donation because of poor corneal function. Generally speaking, it is valuable to harvest corneal epithelium within 6 hours and 12 hours after death in winter. Corneal epithelium is intact, the stroma is transparent and the thickness is constant (no edema). If the fresh corneal material is treated with preservation solution or cryogenic treatment, it can be preserved for several days or weeks. However, the corneas of the following donors cannot be used for transplantation: 1, and some infectious diseases such as AIDS, syphilis, rabies, tetanus, leprosy, diphtheria, viral hepatitis, encephalitis and polio. 2. Malignant tumor has invaded eye tissue, leukemia and Hodgkin's disease. ; 3. Some eye diseases such as anterior segment malignant tumor, retinoblastoma, viral keratitis, corneal degeneration or scar, glaucoma, iridocyclitis, suppurative endophthalmitis and those who have undergone intraocular surgery.

Corneal transplantation is divided into penetrating keratoplasty and lamellar keratoplasty. 1. penetrating keratoplasty is a method of replacing full-thickness turbid cornea with full-thickness transparent cornea. Use a trephine with a certain diameter to drill the diseased full-thickness cornea, then use a trephine with the same caliber or a little larger to drill the donor cornea, and sew the nylon thread of 10-0 on the recipient membrane. According to the surgical purpose, the indications can be divided into optics, therapy, plastic surgery and beauty. Optical corneal transplantation: refers to corneal transplantation for optical purposes (corneal transparency). Common indications are keratoconus, corneal scar caused by various reasons, corneal malnutrition caused by various reasons and corneal endothelial cell failure. Therapeutic corneal transplantation: used to treat corneal diseases, control infection, shorten the course of treatment and save eyeballs. The main indications are suppurative corneal ulcer, ocular chemical injury, silkworm corneal ulcer and corneal limbal degeneration. Plastic corneal transplantation: corneal transplantation aimed at restoring corneal tissue structure, such as corneal thinning and perforation. Cosmetic corneal transplantation: mainly used to improve the appearance of cornea. Suitable for blind patients with corneal leukoplakia. 2. Lamellar corneal transplantation is a kind of partial thickness corneal transplantation, which only removes the superficial tissue of the diseased cornea, keeps the deep intact recipient membrane as the transplantation bed, and then sutures the corneal anterior layer with the same size and thickness from the donor to the recipient corneal wound. Lamellar keratoplasty does not penetrate the anterior chamber, which belongs to extraocular surgery, generally does not disturb the intraocular tissue and has fewer complications. Therefore, lamellar keratoplasty is feasible for those whose corneal lesions do not invade the deep layer of cornea and whose endothelial physiological function is healthy or recoverable. Clinically, it is often used for superficial corneal macula or corneal dystrophic opacity, progressive keratitis or ulcer, corneal fistula's disease and corneal tumor.

Corneal transplantation is only a part of corneal transplantation, and postoperative treatment and self-care also play an important role in the success of corneal transplantation. The patient can leave the hospital about 1 ~ 2 weeks after corneal transplantation. Because the immune rejection of corneal transplantation is the main cause of postoperative failure, patients need to continue taking drugs after discharge. Generally, it takes three months to apply corticosteroid eye drops or cyclosporine A locally after operation. It takes one month to use immunosuppressive drugs such as glucocorticoid all over the body, and it takes longer for some patients with poor corneal condition. Because there are many side effects of this kind of drugs, the time, method and dosage should be strictly in accordance with the doctor's advice, and it is not allowed to add or subtract at will, and it is not allowed to stop taking drugs at will to prevent adverse reactions such as hormone rebound. Patients should be followed up on time, especially once a week at the beginning of discharge; If there are no special circumstances, it can be reviewed once a month after one month, and once every three months after the corneal suture is removed. If there are special circumstances, you need to return to the clinic at any time. The suture time of penetrating keratoplasty is generally 6-65438+2 months after operation; Lamellar keratoplasty is usually performed 3-6 months after operation, but the specific time is determined by the doctor.

relevant issues

Living people can't donate corneas

According to the law of our country, the living can't donate corneas before their death, because if they donate corneas, their eyes will be invisible and become disabled. This is against morality and ethics, so it is not allowed. But you can fill in the letter of intent to donate cornea and donate it after death.

How do people who donate corneas go through the formalities of donating corneas?

Donating corneas means donating after death, but the relevant procedures should be done before death.

What are the requirements of people who donate corneas?

Donors must be voluntary during their lifetime, or with the consent of their families after their death, with the principle of respecting voluntariness. The best age is 6 to 60. If used in medical research, it is not limited by age and disease.

Where can I get the donor's cornea?

Cornea is restricted by many conditions, such as death certificate, infectious disease, time of death and so on. , so it is unlikely to be filmed at home.