Types of keratoplasty
Keratoplasty is performed in cases of constant opacity of the cornea. During the operation, the modified cornea is dissected and on its place is transplanted the corneal specimen disk of appropriate shape and size – the corneal graft. Corneal graft can replace the entire cornea or some of its modified layers.
Impaired vision caused by corneal diseases (become apparent in its opacity or shape change)usually have a component of irreversibility, and are not adjusted by glasses or contact lenses. In such cases, keratoplasty surgery becomes the only possible solution to restore vision of the sick person and return him or her to a normal social life.
Keratoplasty in its aims can be optical, tectonic, therapeutic and cosmetic. Most often it is possible to achieve several purposes during one operation.
- is conducted to improve visual acuity, to restore or enhance the transparency of the cornea by full or partial replacement of the modified corneal tissue of the patient by a specimen – the corneal graft. The most common indications in this category are: keratoconus; keratoglobus; bullous keratopathy; epithelial-endothelial corneal dystrophy; primary (congenital-hereditary or familial) corneal dystrophies; various resistant wall-eyes and corneal scars obtained as a result of keratitis, burns or injuries.
Tectonic (reconstructive) keratoplasty:
- is indicated to preserve the anatomy and integrity of the cornea of patients with discernible thinning and / or development of descemetocele, and also to restore anatomy of the eye, for example, corneal perforation.
Therapeutic (medical) keratoplasty:
- is indicated to stop the (total or partial)progression of the disease, to restore the defected area of the cornea by removing corneal tissue inflamed area, which does not respond to treatment with antibiotics and antiviral drugs. The most common indications in this category include: heavy fresh (and very heavy) burns of the cornea; corneal ulceration threatening penetration into healthy tissue and / or perforation; neurotrophic and neuroparalytic keratitis; corneal tumors, limb or sclera tumors; fistula and perforation of the cornea; deep corneal dystrophies; severe keratitis of various etiology (herpes, tuberculosis, bacterial, fungal, acanthamoeba, and others); epithelial cysts of anterior chamber of the eye; perforated eye injuries; keratomalacia and intracorneal abscess.
- is indicated to improve the appearance of the patient with scars on the cornea, which led to the appearance of coarse, visible to others, wall-eye or swollen areas on the surface of the cornea; for reconstruction (recovery) of corneal defects and deformations, both congenital and acquired due to damage and disease.
Classification of keratoplasty according to the size of the cornea area that needs replacement:
- Total - to the size of the corneal graft is equivalent to the size of the patient's cornea (with optical aim it is almost never applied);
- Subtotal - a large area of the patient's cornea - greater than 5 mm needs a replacement;
- Local – a smaller area of the cornea of the patient requires replacement.
Type of surgery:
Keratoplasty is determined by the type of surgery (penetrating keratoplasty, layered lamellar keratoplasty; intralamellar, endothelial keratoplasty), the choice of the type of surgery depends on the patient's exact cornea disease.
1. Penetrating keratoplasty (is replaced the entire thickness of the cornea of the patient) – is a microsurgical operation, during which the modified area of the patient's cornea is replaced by a corneal graft. The operation can significantly improve vision in cases of diseases that affect the cornea, and to restore in cases of damage acquired due to eye injuries. It is usually performed with an optical purpose, but sometimes it is performed with cosmetic or therapeutic purposes. Penetrating keratoplasty is performed for patients with opacity of all layers of the cornea as a result of undergone injuries of the eye cornea, with keratoconus, corneal dystrophies, in cases of corneal burns, severe keratitis.
Surgery process through penetrating keratoplasty:
This type of surgery is usually performed under general anesthesia. Penetrating keratoplasty operation involves excision of the entire depth of the damaged corneal tissue with a round trephine (diameter of which is 6-8 mm) and its replacement with a corneal graft. Standard penetrating keratoplasty involves replacing 2/3 of the central part of the cornea with a transparent corneal graft of the relevant size that is held in a place, being fixed to the periphery of the undamaged cornea of the patient with continuous or interrupted sutures of very thin synthetic threads, which are significantly thinner than human hair. At the early stage of engraftment antimicrobial treatment is placed on, glucocorticoids are taken to avoid possible rejection. The period for which the stitches are sutured may take up to 6 months. At the end of 6 months it is necessary to remove stitches. After removal of sutures during several years the operated patients is recommended to avoid heavy physical activities and stress, as the result of which the eye is influenced physically.
The method of excision of the corneal disc with a metal knife – trephine through penetrating keratoplasty is considered to be a mechanical "traditional" way. The result of this operation depends on many factors: the initial condition and the patient's corneal disease, on the patient's general state, the presence of underlying disease, the nature of the tissue healing. The cornea is a relatively simple cloth and contains no blood vessels, so in most cases a corneal graft perfectly survives. It should be noted that in case of keratoconus and some other diseases, the possibility of transparent engraftment increases to 95%.
Excision of corneal discs using a femtosecond laser is an ultra-modern way of penetrating keratoplasty. Compared with a metal knife, trephine, high-precision laser is always preferred due to the cutoff of high accuracy, ability to create a complex profile of the side cut for better adaptation and sealing of the corneal graft, to obtain best visual functions and reduce the rehabilitation period, to reduce the level of complications during as well as after the surgery (intraoperative damage of the iris and the crystalline lens, a high induced astigmatism). This new way of penetrating keratoplasty is called Femto-UPC.
Penetrating keratoplasty is the main method of dealing with blindness in case of the most various diseases of the cornea and the anterior segment of the entire eyeball.
2. Layered, lamellar keratoplasty (anterior layered and lamellar posterior keratoplasty). Is indicated in cases where there is no need to affect all layers of the cornea. During the front lamellar keratoplasty operation are replaced only the front corneal layers (300-400 microns); while the posterior lamellar keratoplasty are replaced the posterior corneal layers (100-170 microns).
Surgery process through lamellar keratoplasty:
This type of surgery is performed under local anesthesia. The surgeon cuts away the surface layer of the opacified cornea, taking into account the depth and limits of the altered tissue. Into the defect formed after the cut, is put a transparent corneal graft, similar in shape and thickness to the cut layer. The corneal graft is fixed with a single continuous suture or interrupted sutures. The optical lamellar keratoplasty is performed using circular, centrally placed corneal grafts. Fiberwise therapeutic implantation is carried out both in the center and on the periphery of the cornea within the limits of the site its damage.
Carrying out this type of operation is possible using conventional microsurgical methods (trepanning, keratotomy). But, currently, the most progressive and effective to use is a surgical femtolaser installation. Because only it can accurately cut to a predetermined depth the damaged area of the cornea of the patient, as well as cut a corneal graft of the same shape and thickness.
3. Intrachamber, endothelial keratoplasty.
Modern type of keratoplasty operation is used in case of endothelial-epithelial corneal dystrophy, to restore its transparency. Posterior keratoplasty involves replacing one of the patient's endothelial layer of the damaged cornea with a corneal graft (110-140 microns).
Layered, lamellar keratoplasty and endothelial keratoplasty are modern hi-tech microsurgical operations, during which are selectively replaced only the defected components of the cornea, and its healthy parts remain intact. These précised techniques assist rapid healing, need less restrictions in the postoperative period, and reduce the risk of eye damage in the future.
In all kinds of keratoplasty is used a corneal graft made and examined by us according to international standards, as the result of the operation undoubtedly depends on the characteristics of the medication being used.