What Are Corneal Implants?

Keratosis and cataract are the main causes of blindness. It can be cured by corneal transplantation. The appearance of artificial cornea has freed corneal transplantation from the problems of lack of donors and low success rate of transplantation. hope.

Keratosis and cataract are the main causes of blindness. It can be cured by corneal transplantation. The appearance of artificial cornea has freed corneal transplantation from the problems of lack of donors and low success rate of transplantation. hope.

Chinese name

Artificial cornea

Foreign name

Artificial cornea

Brief introduction

Corneal-like products

Material

Medical polymer materials

Outlook

The ideal artificial cornea

Basic introduction of artificial cornea

KERATOPROSTHESIS

Over 10 million people in the world are caused by corneal disease, which is the second leading cause of blindness after cataracts. 80% of them can be blinded by corneal transplantation. However, traditional corneal transplantation has two major drawbacks. One is the difficulty in obtaining the corneal donor, and the other is the low success rate of the operation. The appearance and application of artificial cornea has brought hope to blind corneal patients.

The world's first artificial cornea, which was independently developed by Chinese scientists, has successfully completed clinical trials. The total effective rate after artificial corneal transplantation reached 94.5%, and the effect is close to the human cornea. This product is a cutting-edge product of tissue engineering and can replace human corneal donation. This is the world's first and a high-tech artificial corneal product that has completed clinical trials. This product is independently developed by Chinese scientists and has complete independent intellectual property rights.

History of artificial cornea development

Artificial corneal development background

Since the French ophthalmologist Pellier de Quengsy first proposed the implantation of glass slides in opaque corneas in 1789 to restore vision, and Weber first implanted a piece of crystal glass in the cornea of patients in 1871, pioneering the history of artificial corneal implantation. The development has gone through more than 200 years. It has experienced 4 periods of exploration, stagnation, recovery and development. There have been new developments in material design, manufacturing technology, surgical skills, and postoperative management.

Basic structure of artificial cornea

Common materials for optical lens columns include poly (hydroxyethyl methacrylate) (PHEMA), polymethyl methacrylate (PMMA), silicone gel, glass, etc .; common materials for peripheral brackets include ceramic, fluorocarbon polymer, and hydroxyapatite , Biological materials, polytetrafluoroethylene, etc.

Corneal sheet design

Among the corneal designs, AlphaCor, Dohlman-Doan, and Osteo-Odonto have been more successful, and have been approved by the FDA to enter the clinical stage.

AlphaCor artificial cornea

In the early 1990s, Chirila et al. [13] of the Lion Eye Research Institute of Australia made PHEMA hydrogel as an integrated artificial cornea AlphaCor, also known as "Chirila" cornea, and conducted the first human trial in 1998-02. Subsequently, clinical trials around the world have begun, and this kind of cornea has become the most widely used cornea in clinical practice. AlphaCor has a sponge-like support and optical column. The two parts are composed of PHEMA hydrogels with different water contents. They are connected by an interpenetrating network structure and can withstand higher pressure and tension. Because the lens column and the surrounding bracket are made of the same material (PHEMA hydrogel), the physical and chemical properties are similar, which solves the problem of combining the two parts, and also reduces the probability of bacterial infection at the binding site. Pigmentation.

Dohlman-Doane artificial cornea

The Dohlman-Doane artificial cornea is a collar-one button type, which is composed of PMMA, including the front plate, trunk and back plate. Type I is mainly used in patients with sufficient tears and maintaining moisturized eyes. Type II has an additional front pillar that protrudes from the eyelid and is used in patients with end-stage dry eyes. The prognosis of this artificial cornea varies depending on the preoperative diagnosis and the degree of ocular surface inflammation. The prognosis is best for patients who have failed multiple rejections and have no severe inflammation before surgery. The prognosis of Stevens-Johnson syndrome is poor.

Osteo-Odonto artificial cornea Osteo-Odonto artificial cornea is the earliest and most successful artificial cornea. It uses autologous tissues (tooths) as peripheral scaffolds and PMMA as an optical lens column. This special type of bone-tooth shape has increased tolerance to cornea , Better integration with the host, play a positive role. Due to the complicated surgical procedures and greater trauma, this artificial cornea is used only when there is no other way. Compared with other artificial corneas, the long-term retention rate of this artificial cornea is high. Some scholars have reported that the 18-year retention rate is 85% and 75% of patients have vision of 6/12 or better. The main problems of this artificial cornea are limited postoperative visual field and glaucoma. , Complications such as dissolution of bone and tooth layer, inability to measure intraocular pressure.

Other artificial corneas include BIOKOP artificial cornea, Seoul-type artificial cornea, Cardona artificial cornea, MICOF artificial cornea and so on.

Due to the shortcomings of the "mirror column-bracket" type, the strength of the joint is poor, and the aqueous humor leaks. Many scientists have turned their attention to the traditional "integrated" structure. U.S. scientists have used the new composite hydrogel Duoptix to create an integrated artificial cornea, which is undergoing animal tests and performs well.

Prospects of artificial cornea

The ideal artificial cornea and prospects

A variety of artificial corneas have been used clinically, but their materials have not reached the ideal requirements, and due to the late complications of artificial cornea: corneal dissolution, implant drainage, aqueous humor leakage, endophthalmitis, post-corneal hyperplasia Membrane, glaucoma, etc., are only suitable for patients with corneal opacity blindness in conventional corneal transplantation, which is generally only used as a last resort. The ideal artificial cornea should have the following characteristics: excellent optical characteristics, stable physical and chemical properties. It can coexist with autologous corneal tissue for a long time, and it can be closely combined. No adverse reactions and fewer complications. The operation is simple, easy to make, and economical.

In the future, the research focus of artificial cornea is to focus on joint research by experts in biomaterials, cell biology, molecular biology, and clinical medicine, choose truly biocompatible materials, improve the integration of optical lens columns and peripheral scaffolds, and more importantly, the peripheral Integration of scaffolds and recipient tissues.