In January last year, Yao Beina, a famous singer who died tragically of breast cancer, donated her corneas to help three eye patients in Shenzhen, Chengdu and Wuhan regain their sight. in January 2016, doctors brought Yao Beina’s remaining left ring-rimmed cornea to Guiyang for transplantation into the eyes of a 67-year-old woman in Zunyi County, allowing the old woman to see again. How much do you know about corneas?
1. How many people can be saved by a pair of corneas and on what basis is the number of people saved determined?
Generally speaking, corneal transplantation is “one-to-one”, which means that a pair of corneas from one donor, after being tested and qualified by an eye bank, can restore the sight of two patients who are corneal blind. However, in recent years, as corneal transplantation techniques have improved, and because of the scarcity of corneal donors in China, our Chinese corneal transplant surgeons have the ability and must effectively utilize all parts of each donor cornea.
The surgeon usually cuts and transplants the donor “site” according to the location and nature of the patient’s corneal lesion. Simply put, a corneal transplant is like “replacing a watch mask” but not “replacing all of it” because of the chance of rejection and the need for tissue healing. If the central part of the cornea is bad or opaque, only the central part will be replaced (penetrating keratoplasty); if the limbus is bad, only the peripheral part will be replaced (corneoscleral lamellar transplantation, etc.); if the superficial layer is bad, only the superficial layer will be replaced (anterior lamellar transplantation); if the inner deep layer is bad, only the deep part will be replaced (corneal endothelial transplantation), which is called “component corneal transplantation”. ” concept.
In the reality of domestic eye banks, after obtaining high quality corneal donors, they are generally used first “one-to-one” for “penetrating corneal transplantation” or “endothelial corneal transplantation “The remaining “leftovers” (cyclic corneoscleral material or lamellar anterior lamellar stromal material) are well preserved by the eye bank and used for other parts of the patient’s treatment.
This has led to the “one cornea for many patients” story that has been widely reported in the media. Many of the corneal transplant surgeons in China are trying to “make more efficient use of the limited donor” rather than “to save the number of patients”. It is not impossible for one cornea to be used for 10 patients if a specific patient is selected.
Therefore, it is more scientific to say that “after screening by eye banks and clinicians, a pair of qualified corneal donors can be used to save at least two patients”.
2. How long can corneas be preserved?
Modern eye banks have several methods of preserving the acquired corneas, depending on the quality of the donor and the condition of their own equipment.
(1) Wet room preservation of the whole eye: generally used within 48 hours for “penetrating/endothelial transplantation”, etc. It is usually used in primary eye banks without conditions, or for short “transfers” of donor eyes.
(2) Medium-term preservation with medium-term preservation solution: Widely used by most eye banks for “penetrating/endothelial transplantation”, etc. within 2 weeks.
(3) Medium- and long-term preservation with organ culture method: used within 45 days for “penetrating/endothelial transplantation”, etc. Donor materials are relatively abundant in some European countries and are preserved using this method in order to “find” patients for a longer validity period.
(4) Liquid nitrogen deep cryogenic long-term preservation: more than one year, after re-temperature “activation” can also be used for “penetrating corneal transplantation”, etc., a small number of eye banks use.
(5) cryogenic glycerol/freeze-drying long-term preservation: more than one year, for quality can not meet the “penetrating/endothelial transplantation”, medium-term long-term preservation of over limit or “surgical residual material” can be used for long-term preservation of this method, for “lamellar The method is used for “corneal transplantation” or certain “emergency surgery” for the purpose of preserving the eye.
For high quality fresh corneal material obtained by the eye bank, the method of “medium-term preservation with medium-term preservation solution” is generally used, with the surgery completed within 2 weeks and the “residual material” continuing to be “medium-term preserved” according to time. “After the time limit is exceeded, it can be “long-term preservation with cryoglycerin”.
3. What are the requirements for donating corneas?
It can be said that “anyone” can donate corneas. However, what the donated cornea is used for and whether it can be used clinically depends on eye bank testing and evaluation by eye bank technicians/clinicians.
Eye banks have strict selection criteria for corneal material for clinical transplantation. The “absolute contraindications” for donors include: infectious diseases of blood origin such as AIDS, hepatitis B and C; hematologic malignancies such as leukemia and malignant lymphoma; and acute systemic and ocular infectious diseases.
Age requirements for “penetrating corneal transplantation” are generally 2 to 70 years old (too young for poor tissue toughness, too old for poor corneal endothelial function, etc.), but are also determined by the eye bank’s testing of the material. There are also many other “relative contraindications” for donors, which are considered by the surgeon based on the recipient patient and the eye bank’s donor test results. Because of the relative scarcity of domestic donors, many eye banks or surgeons are appropriately relaxed in the application of relatively contraindicated materials.
Eye bank staff and technicians make predictions about the possible use of corneas by asking questions, reviewing relevant laboratory reports and eye examinations before donor registration and removal of donor eye tissue, and informing of the various possibilities, and also allowing the donor or family to decide whether to donate.
For those corneal/eye materials that cannot be used clinically, eye banks use them for teaching or research, which is also of great significance to the development of medicine. For example, the “retinal pigment epithelial cell line”, which is now widely used in basic ophthalmic research worldwide, originated from a 19-year-old boy who died unexpectedly in the United States, and his contribution is “worldwide”.
4.Can people with myopia, hyperopia and amblyopia donate?
Nearsighted, farsighted and amblyopic people can be corneal donors as long as the cornea itself is not diseased and does not affect clinical applications. Others including cataract, glaucoma and people after inner eye surgery can also donate their corneas after death to save patients with corneal disease.
5. Why is corneal surgery the most successful of organ transplants?
Corneal tissue is special because there are no blood vessels or lymph, and it is “relatively immune immune” and has a low rejection rate after transplantation. Corneal transplants in general do not require a blood match. In general, the success rate of corneal transplantation surgery is above 90%.
6.What are the requirements for corneal donation in China?
Currently there is no national legislation on corneal donation in our country. However, with the development of society, public awareness of donation has increased year by year. Non-profit hospitals, Red Cross societies and other organizations around the world have started to take up this part of social responsibility, helping or directly setting up formal eye banks to build bridges between corneal donors and the majority of corneal patients, fulfilling the last wishes of kind donors and helping blind corneal patients regain their sight.
The requirements/processes for corneal donation vary from one Red Cross or eye bank to another, but generally include: the donor himself or herself and the immediate family member entrusted to sign the “Corneal Voluntary Donation Consent” and seek the unanimous consent of all close immediate family members; the “Corneal Donation Card” with contact information of the eye bank or relevant organization is issued;
After the death of the donor, the principal contacts the eye bank or related organization; the eye bank or related organization staff further confirms on site and then removes the eye tissue and returns it to the eye bank, where it is tested to exclude contraindications and assigned for clinical use; the eye bank collects the use of corneal material and informs the Red Cross or the donor’s family of the situation.