Among ophthalmic diseases, there are more than 3 million patients who are blind due to corneal diseases, of which about 80% can be removed from blindness and restore their vision through traditional corneal transplantation.
A comparative study shows that full-thickness keratoplasty can achieve better clinical results and fewer complications for patients with corneal ulcer but not perforation caused by infection. It can be seen that traditional keratoplasty has achieved a high success rate in the treatment of suppurative corneal ulcer, keratoconus, corneal leukoplakia, etc.
However, for patients with severe chemical injury, thermal burn, explosive injury and some autoimmune diseases, the success rate of traditional corneal transplantation is not high, and the current lack of corneal donors in China, some regional hospitals can not complete corneal transplantation, and the discovery of artificial cornea brings hope to the recovery of vision of such patients.
The artificial cornea is made of heteroplastic materials, which is a special device used to replace the turbid cornea to improve the vision of patients. The artificial cornea can be divided into soft and hard according to different materials. The soft cornea is represented by AlphCor artificial cornea. This kind of artificial cornea has high requirements on the patient's ocular surface and is expensive, which limits its clinical application.
At present, the hard artificial corneas on the market include Mich artificial cornea, Boston artificial cornea and bone-tooth artificial cornea. So, what are their indications? Which artificial cornea has more extensive indications? What are the indications for using artificial cornea?
Mich artificial cornea
Shape design and material: Mih artificial cornea is composed of titanium metal stent and PMMA lens column. PMMA is an inert and transparent biological material with good biocompatibility.
Indications: Mich artificial cornea has a wide range of indications and is suitable for patients with binocular corneal blindness who are difficult to succeed in corneal transplantation, including corneal transplantation failure, severe keratoconjunctival scar vascularization caused by chemical injury, thermal burn, explosive injury, etc., eyelid atresia, severe autoimmune diseases (such as Stevens-Johnson syndrome and cicatricial pemphigoid), corneal blindness caused by end-stage dry eye, etc.
Boston artificial cornea
Shape design and material: Boston artificial cornea is made of PMMA. At present, Boston type I artificial cornea is widely used. Botton type I artificial cornea is composed of anterior disc, optical prism, posterior disc and titanium fixing ring. The shape of Botton II artificial cornea is roughly the same as that of Boston I artificial cornea. The main difference is that the central cylindrical lens of type II artificial cornea protrudes forward 1 mm or 2 mm from the front surface.
Indications: Boston artificial cornea is mainly used in cases of corneal transplantation failure, but it is difficult to apply in cases with poor ocular surface conditions, such as chemical burns and other complex corneal blindness. Although there are very successful clinical application reports abroad, due to the need for corneal allografts as artificial corneal carriers, combined with the shortage of corneal materials in China, the clinical promotion is limited.
Bone-tooth artificial cornea
Shape design and material: The bone-tooth type artificial cornea is made of autogenous teeth as the peripheral scaffold material, and the center is an optical prism.
Operation indications: patients with severe late Stevens-Johnson syndrome, cicatricial pemphigoid, epidermolysis bullosa, trachoma, chemical or mechanical injury, eyelid loss, dry eye, and multiple corneal transplantation failures, their vision should not be lower than light perception.
The procedure of OOKP artificial cornea surgery is complex and difficult to operate. It requires multidisciplinary cooperation and is difficult to promote clinically.
AlphaCor artificial cornea
Appearance design and materials: AlphaCor artificial cornea consists of an optical center and peripheral materials. The optical center is similar to a soft corneal contact lens, and the peripheral materials are similar to a sponge structure. The material is polyvinyl alcohol copolymer hydrogel.
Operation indication: The operation indication of AlphaCor artificial cornea is alkali burn.
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Different types of artificial corneas have different indications. At present, there is no uniform standard for the selection of surgical indications. Clinicians generally choose appropriate artificial corneas according to experience and the conditions of the patient's eyes.
At present, the accepted surgical indications for the use of artificial cornea are as follows
① Blindness in both eyes. Manual vision or worse
② There is no hope of success in corneal transplantation, or corneal transplantation can be performed but can not maintain corneal transparency, such as Stevens-Johnson syndrome, severe dry eye such as cicatricial pemphigoid, alkali burn, etc., which causes severe keratoconjunctival scar vascularization, eyelid atresia, multiple penetrating corneal transplantation failures, etc
③ For adults who can cooperate with the treatment, if percutaneous kyphoplasty (PKP) fails, corneal vascularization will be more serious, and artificial cornea will have a better prognosis than PKP again, which can improve the quality of life of patients
④ Those whose visual function, color vision, electrophysiology and B-ultrasound examination show that the structure and function of retina are still good
⑤ Normal intraocular pressure or glaucoma, the condition is stable after drug control. If the artificial corneal lens column penetrates through the eyelid, the intraocular pressure must remain normal without any medicine
⑥ The primary disease is stable, without active inflammation and infection
⑦ Regular follow-up