The development of artificial cornea has probably gone through four stages.
Since Queensy first proposed the idea of replacing turbid cornea with glass lens in 1789, it has been an exploration stage of artificial cornea since the early 20th century. Since then, it has experienced a stagnation period before the 1930s, a recovery period from the 1930s to the 1960s, and then the artificial cornea has entered a rapid development stage.
Before the official launch of Mihm artificial cornea, Boston artificial cornea, Pintcucci artificial cornea (Dacron) and AlphaCor artificial cornea have reached full commercial application worldwide; In addition, bone tooth keratoprosthesis is also widely used.
At present, Boston keratoprosthesis is the most widely used one in the world, and about 3500 cases of Boston keratoprosthesis have been implanted worldwide. Although Boston artificial cornea has been used clinically for 40 years, it was only in 2004 that the first Boston artificial cornea implantation was carried out in China by Orbis international training institutions, and the number of operations after that did not increase due to related factors (such as more complications, need for donor cornea as a carrier, less indications, etc.). It is noteworthy that the buckle type artificial cornea in China is a Boston I artificial cornea.
AlphaCor type artificial cornea is mainly used for patients with good tear secretion function in the surgical eye, and occasionally for patients with moderate dry eye. At present, hundreds of patients worldwide have been implanted with AlphaCot keratoprosthesis, and the longest follow-up time is more than 7 years.
OOKP keratoprosthesis was first used in clinic in 1960s. It has been improved for many times and is now mainly used in Australia, Germany, England, Japan, India and Singapore.
Although the artificial cornea has made rapid development, how to maintain the best corrected vision of patients after surgery and how to deal with various complications are still the biggest problems faced by each type of artificial cornea.
Some clinical observations have proved the safety of AlphaCor artificial cornea, but some patients still have complications such as conjunctival flap leakage, thinning and dissolution of anterior corneal matrix, and formation of artificial corneal fibrous exudate membrane (RPM). Among them, RPM and matrix thinning and dissolution may lead to refractory glaucoma in some patients, or even artificial cornea excretion.
Fortunately, in recent years, with the extensive application of Boston keratoprosthesis, the use of AlphaCor keratoprosthesis has decreased significantly. Compared with AlphaCor type artificial cornea, Boston 1 type artificial cornea can be completed in a single operation, which is simpler and more effective.
However, in fact, the long-term efficacy of Boston keratoprosthesis still needs to be observed, and its complications are also many: RPM, glaucoma, persistent epithelial defect, aseptic vitreous inflammation, endophthalmitis, retinal detachment, etc. The prevention and treatment of these complications directly affect the correction of postoperative visual function.
Among all postoperative complications of Boston keratoprosthesis, RPM is the most common, and its incidence rate can be as high as 24-65%. At the same time, glaucoma should not be underestimated in the complications of Boston keratoprosthesis implantation. It is even the biggest challenge to maintain visual function after surgery. This is not only because its impact on visual function is irreversible, but also because glaucoma is very common after Boston keratoprosthesis implantation. The incidence rate of glaucoma is higher, especially for patients with acid base chemical burns, autoimmune diseases or pre-operative history of glaucoma.
At present, the artificial corneas used in clinic have their own advantages and disadvantages. Whether Boston, OOKP or AlphaCor artificial corneas, their biocompatibility with the body, the complexity of the surgical process, the long-term effect after surgery, the prevention and treatment of various complications after surgery, and the maintenance of optimal visual function after surgery need to be improved. These problems limit the further development and wide application of artificial cornea.
So, who broke the deadlock? On December 7, 2021, the State Drug Administration approved the registration of the innovative product "artificial cornea" produced by our company (Beijing Mihe Medical Instruments Co., Ltd.), which is called Mihe artificial cornea. Its listing has brought positive signals for the development of artificial cornea.
Unlike the aforementioned keratoprosthesis, Mihm keratoprosthesis does not require donor cornea, and has a wide range of indications and few complications. At present, more than 100 patients have undergone Mihm keratoprosthesis implantation, with the longest follow-up time of more than 10 years.
Mih artificial cornea is divided into two parts: a stent and a lens column. The stent is made of titanium metal, and the optical column is composed of polymethyl methacrylate. This artificial cornea is implanted by stages. Through intraocular perfusion and small corneal opening, it can avoid serious intraoperative complications such as expulsion bleeding and water leakage of Boston and AlphaCor artificial corneas to the greatest extent.
In addition, compared with the allograft corneal carrier in Bosoton artificial cornea, it mainly relies on aqueous humor to provide nutrition to maintain its epithelial integrity. Mihm artificial cornea promotes vascularization of the ocular surface as soon as possible by covering the conjunctiva or labial mucosa to maintain the nutrition supply of the anterior lamellar tissue, thereby reducing the possibility of tissue dissolution.
At the same time, the front end of the MIH artificial cornea column is convex, and the rear end is concave, forming a certain diopter. You can flexibly select the appropriate diopter of the optical part and the height of the column according to the length of the patient's eye axis and the thickness of the ocular surface tissue.
In addition, the detachable design can also be disassembled and replaced according to the situation (replacement degree, replacement height and worn lens column) even after surgery, rather than Bosoton artificial cornea. In case of any emergency after surgery, the entire product must be replaced.
In a word, Mihm keratoprosthesis can significantly improve the postoperative vision of patients, and provide hope for corneal blindness patients. For corneal blindness patients, it is the most cost-effective choice.