Speaking of artificial cornea, in addition to the Mihe artificial cornea independently developed by our company, we believe that the most popular one is Boston artificial cornea.
Some media said that this artificial cornea is widely used in the world, but why is it rarely used in China? Today, let's talk about the origin of the legendary Boston keratoprosthesis and why it is not popular with corneal blindness patients in China.
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Boston artificial cornea was invented by Professor Dohlman of Massachusetts Eye and Ear Hospital affiliated to Harvard University. Although it has been used clinically for many years, it was approved by the US FDA in 1992. After approval, the number of cases increased dramatically, from 50 in 2002 to 1161 in 2009. So far, the total number of operations in the world has exceeded 5000.
In 2004, the first operation of Boston Type I keratoprosthesis was performed in China as part of the Obis International Training Program. However, since then, Boston keratoprosthesis has not continued to write the myth of "dramatic increase in cases" in China. What is the specific reason.
Many people do not know that there are actually two types of Boston keratoprosthesis, Boston Type I and Boston Type II.
① Type I is a simple collar button design, which is suitable for keratopathy patients with normal blink and tear function, and has high requirements for eye surface conditions.
② Type II keratoprosthesis is suitable for patients with cicatricial ocular surface disease at the end stage. It has one more protrusion than type I keratoprosthesis, and other structures are the same as type I. Type II artificial cornea has a fatal disadvantage, that is, there are many postoperative complications, so it is not used frequently in clinical practice. Therefore, the so-called Boston keratoprosthesis is actually the Boston Type I keratoprosthesis.
So let's take Type I keratoprosthesis as an example today to explain why Boston keratoprosthesis has not been widely used in China.
Boston artificial cornea is not entirely made of artificial materials. It needs a corneal graft as a carrier between its front and back discs, which is the first reason.
As we all know, China is a country that is extremely short of donor corneas. There are 4 million cornea blindness patients in China. The number of patients who can perform corneal transplantation is less than 10000 every year. Millions of patients are still waiting for donor corneas. Some of them have not even waited for a piece of cornea for more than ten years.
In addition, do not think that everything will be all right when the donor cornea is transplanted. Similarly, the design of the donor cornea implanted in the Boston keratoplasty process will also lead to rejection. Once the rejection is not controlled, the patient will face another or even multiple corneal transplants. Such a vicious circle will only make the patient suffer.
The second reason why Boston keratoprosthesis is not widely used in China is that the surgical method is unreasonable.
First of all, let me show you the operation process of Boston artificial cornea.
① Local anesthesia or general anesthesia is used for surgery
② After anesthesia, an 8.5mm trephine was used to make corneal grafts, and a 3mm trephine was used to drill a small hole in the center of the grafts, through which the artificial corneal lens column can pass.
③ The posterior disc was sheathed to the lens column and fixed with titanium lock catch to assemble the adult corneal graft complex.
④ One or two iridectomy were performed during the operation.
⑤ At the end of the operation, as with traditional corneal transplantation, the artificial cornea corneal graft complex was fixed on the implant bed with 10-0 nylon suture and 16 needles, and the suture was buried.
⑥ Place the bandaged contact lens.
Next, let's talk about why this operation is unreasonable.
Do you know what is the most important of the five layers of cornea? It is the corneal endothelium. It is located at the innermost layer of the cornea. Its "pump" function can make the cornea in a relatively dehydrated state and keep the cornea transparent. Once the endothelial cells are damaged, it will lead to corneal edema, turbidity, and even blindness.
What's worse, for external damage, such as trauma, infection, surgery, multiple degeneration, etc., the defense index of endothelial cells is basically 0.
First, the number of endothelial cells is small. After 2 years old, the number of normal corneal endothelial cells decreased at an annual rate of 0.5%~1%. The density of corneal endothelial cells was 3000~4000 cells/mm2 at<30 years old; 31 ～ 40 years old 3000 ± pieces/mm2; 40 ～ 50 years old 2800 ± pieces/mm2; 51 ～ 60 years old 2600 ± pieces/mm2; 61-80 years old 2160 ± pieces/mm2. Secondly, corneal endothelial cells cannot regenerate. After damage, normal corneal endothelial cells need to expand and migrate to fill the defect area.
Generally speaking, the majority of middle-aged patients use artificial corneas, so their surgical success rate has been decreasing. If there is more serious external force damage at this time, such as the patient has performed surgery, the success rate of surgery will be infinitely reduced.
for instance
Xiao Hua (40 years old) donated a cornea. His cornea diameter is 11.5mm (the normal cornea diameter is 11.5-12mm), and 2800 endothelial cells are active inside. At the second step of Boston keratoplasty, more than 1000 endothelial cells will be "lost" directly.
At step ⑤ of Boston keratoprosthesis transplantation, the endothelial cells will be directly damaged due to suture, repeated extrusion, traction, etc.
In a word, although Boston keratoprosthesis is widely used in the world, it is not suitable for China. Mihm artificial cornea is made of artificial materials without donor cornea, which alleviates the shortage of corneal donors in China and is more suitable for Chinese people to use. If you have patients with traditional corneal transplant contraindications who need to transplant artificial cornea, you can call the official customer service hotline of Mihm Medical 400-111-8801 for consultation~