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Corneal transplantation: procedure, forecast
Medical expert of the article
Transplantation of the cornea (corneal transplantation, through keratoplasty) is performed in order to:
- improve the optical properties of the cornea and eyesight, for example replacing the cornea that has healed after the corneal ulcer; clouded (Fuchs's dystrophy or swelling after cataract surgery); with a turbid cornea in connection with the deposition of opaque abnormal stromal proteins (eg, in hereditary stromal dystrophy of the cornea); with incorrect astigmatism, with keratoconus;
- restore the anatomical structure of the cornea to preserve the eye, for example, in the perforation of the cornea;
- treatment of a disease resistant to therapy, for example, with a severe fungal ulcer of the cornea; or to relieve pain, for example, when feeling foreign body due to recurrent rupture of blisters in bullous keratopathy.
The most frequent indications for corneal transplantation are bullous keratopathy (artifacial, endothelial dystrophy of Fuchs, aphakic), keratoconus, repeated transplantation of tissues, keratitis (viral, bacterial, fungal, Acanthamoeba, perforation) and corneal stromal dystrophy.
Usually, tissue selection is not performed. Cadaver tissue that is suspected of having an infection should not be used.
Transplantation of the cornea can be performed using general anesthesia or local anesthesia with intravenous administration of sedatives.
Local antibiotics are used after the operation for several weeks, and local glucocorticoids - for several months. In order to protect the eye from accidental trauma after transplantation, the patient wears a bandage, glasses and sunglasses. In some patients, in the early postoperative period, corneal astigmatism can be reduced by adjusting the seam or partially removing the suture. Achieving maximum visual acuity can take up to 18 months due to a change in refraction after removal of the suture, wound healing and / or correction of corneal astigmatism. In many patients, earlier and better vision is achieved by wearing rigid contact lenses over the corneal transplant.
Complications include infection (intraocular or corneal), wound filtration, glaucoma, transplant rejection, transplant failure, high refractive error (astigmatism and / or myopia), and relapse (eg, herpes simplex, hereditary stromal dystrophy of the cornea).
68% of transplant rejections are reported. The patients develop a decreased vision, photophobia, pain in the eye and redness of the eye. Transplant rejection is treated locally with glucocorticoids (eg, 1% prednisolone hourly), sometimes with an additional periocular injection (eg, 40 mg methylprednisolone). If transplant rejection is severe, glucocorticoids are additionally administered orally (eg, prednisolone 1 mg / kg 1 time per day) and sometimes intravenously (eg, methylprednisolone 3-5 mg / kg 1 time per day). Usually the episode of rejection is reversible and the function of the transplant is completely restored. A transplant can become nonfunctional if the episode of rejection is severe or long-lasting, and after many episodes of transplant rejection. A repeat transplant is possible, but the long-term prognosis is worse than at the first transplant.
Prognosis of corneal transplantation
The frequency of favorable long-term outcomes of corneal transplantation is more than 90% with keratoconus, corneal scars, early bullous keratopathy or hereditary stromal dystrophies of the cornea; 80-90% - with more advanced bullous keratopathy or inactive viral keratitis; 50% - with active corneal infection; from 0 to 50% - with chemical or radiation injury.
The overall high success rate of corneal transplantation is associated with many factors, including avascularity of the cornea and the fact that the anterior chamber has venous, but not lymphatic drainage. These conditions contribute to low immunological tolerance. Another important factor is the effectiveness of glucocorticoids used locally or systemically to treat transplant rejection.
Transplantation of the limbal stem cells of the cornea
Transplantation of the corneal limb stem cells surgically replaces defective stem cells on the periphery of the cornea, when the host's stem cells are unable to recover from damage. Constant non-healing epithelial defects of the cornea can be caused by such conditions as severe chemical burns and expressed intolerance to contact lenses. These defects result from the inability of the epithelial stem cells of the cornea to regenerate. Untreated, permanent, non-healing epithelial defects of the cornea are susceptible to infection, which can lead to scarring and / or perforation. Stem cells of the corneal epithelium are located at the base of the epithelium on the limb (where the conjunctiva borders on the cornea). Since the corneal transplant is used only in the central region of the cornea, treatment of permanent non-healing epithelial defects requires transplantation of the corneal limbal stem cells. Lymphal stem cells of the cornea can be transplanted from the patient's healthy eye or from the corpse's donor's eye. Damaged epithelial stem cells of the patient's cornea are removed by partial excision of the limbus (epithelium and superficial limb stroma). Donor limbal tissue is sewn into the prepared bed. Transplanted epithelial limbal cells form new ones that cover the cornea, healing its epithelial defects.