Cornea transplantation

Generality

Cornea transplantation, also known as keratoplasty, is the partial or total replacement surgery of the cornea; this intervention is used in cases of damaged or no longer functional cornea, to replace it with a similar healthy element, synthetic or taken from a recently deceased donor.

The most common condition requiring corneal transplantation is keratoconus.

There are three types of corneal transplantation: perforating (or penetrating) keratoplasty, lamellar keratoplasty and endothelial keratoplasty.

After the operation, the patient must follow some important medical indications, to avoid unpleasant complications.

A transplanted cornea can last up to 25 years.

What is cornea transplant?

Corneal transplantation, or keratoplasty, is the surgical procedure by which the operating doctor provides total or partial replacement of the original cornea, no longer functional and heavily damaged, with a similar healthy element, of synthetic origin or coming from a deceased donor recently.

WHAT IS THE CORNEA? A BRIEF REVIEW

The cornea is the transparent and multilayer membrane, which resides in the anterior part of the eye and covers the iris and the pupil.

Devoid of blood vessels (therefore not vascularized), this particular membrane represents the first "lens" that light meets when it reaches the eye.

The functions of the cornea, which deserve a special mention, are at least three:

Protection and support of eye structures;
Filtration of some ultraviolet wavelengths → the cornea allows light rays to pass through the eye tissue, rather than being reflected or absorbed.
Refraction of light → 65% to 75% of the eye's ability to converge the light rays coming from the outside onto the fovea, or the central region of the retina.

uses

The cornea is a very delicate area of the eye and has very little self-repair capacity.

This explains why an injury against him makes the transplant operation indispensable.

The most common medical conditions that require corneal transplantation are:

Keratoconus : it is, by far, the main cause of corneal transplantation;
Degenerative diseases of corneal tissue;
Corneal perforation;
Corneal infections that do not respond to any antibiotic treatment;
The presence of scars on the cornea.

Procedure

Eye surgeons can perform corneal transplant surgery in at least three modalities, whose name is:

Perforating keratoplasty or penetrating keratoplasty ;
Lamellar keratoplasty ;
Endothelial keratoplasty .

While piercing keratoplasty involves the replacement of an entire corneal thickness and represents the oldest operating mode, lamellar keratoplasty and endothelial keratoplasty involve the replacement of some cornea layers and represent the most modern intervention modalities.

PERFORATING OR PENETRATING KERATOPLASTY

For perforating keratoplasty, the operating doctor uses a sort of cutter, called a trephine, through which he cuts the damaged cornea section, for its entire thickness.

After the resection, it provides for the removal of the damaged corneal section and the replacement of the latter with the "new" one, synthetic or taken from a donor.

The grafting of the "new" cornea requires the application of different stitches, the removal of which, in some situations, can take place even after 12 months from the procedure.

The operation of perforating keratoplasty may occur under general anesthesia or under local anesthesia: in the first case, the patient is unconscious and insensitive to pain for the entire duration of the operation; in the second case, instead, he remains conscious during the operation, but, nevertheless, he does not feel any pain.

A classic operation of perforating keratoplasty lasts 45-60 minutes, including anesthesia.

As a rule, one-night hospitalization is envisaged to allow the patient to recover from anesthesia and from the very first effects of the surgical procedure.

LAMELLAR KERATOPLASTY

Through lamellar keratoplasty, eye surgeons provide the transplantation of the outer and possibly central layers of the cornea.

The instrumentation used may consist of the aforementioned trephine or a special laser designed for this purpose.

The resection of the damaged cornea layers is followed by the application of healthy cornea layers, taken from a donor or of synthetic origin.

The grafting of healthy cornea layers requires the creation of different sutures, exactly as in the case of penetrating keratoplasty.

There are two subtypes of lamellar keratoplasty:

Anterior lamellar keratoplasty : consists in the removal and replacement of the outer layers of the cornea.
Deep anterior lamellar keratoplasty : consists in the removal and replacement of the outer and central layers of the cornea.

At the end of lamellar keratoplasty procedures, the patient can return home a few hours after the end of the procedure, provided that the conditions are stable.

ENDOTHELIAL KERATOPLASTY

Through endothelial keratoplasty, eye surgeons provide the transplant of the inner layers of the cornea and possibly the so-called corneal stroma (NB: an anatomical description of the cornea is present here).

As in the case of lamellar keratoplasty, the instruments used may consist of the usual trephine or a laser beam designed for this purpose.

After the resection of the damaged cornea layers, it follows the application of the healthy cornea layers, taken from a donor or of synthetic origin.

No stitches are needed for the grafting of the healthy cornea layers, but an air bubble, created specifically to keep the corneal transplant in place. This bubble is reabsorbed autonomously within a few days, the time required for the graft to attach itself definitively to the rest of the cornea.

There are two subtypes of endothelial keratoplasty:

Endothelial keratoplasty with stripping (or stripping) of the Descemet membrane : consists in the replacement of the innermost layers of the cornea and 20% of the corneal stroma.
Endothelial keratoplasty of Descemet's membrane : it consists of the only replacement of the innermost layers of the cornea.

At the end of endothelial keratoplasty procedures, the patient can return home a few hours after the end of the procedure, provided that the conditions are stable.

Post-operative phase

Immediately after the corneal transplant procedure, the patient:

He must keep the protective bandage, applied in defense of the operated eye, for at least an entire day;
You may experience mild eye pain. It's normal;
He may suffer from blurred vision. It's normal.

POST-OPERATION RECOMMENDATIONS

Once at home, the patient must pay attention to:

Don't rub your eyes;
Do not make excessive physical efforts and do not lift weights;
Don't go to dusty, polluted or smoke-ridden places;
Use sunglasses, as long as the sun causes discomfort;
Do not practice contact sports until otherwise instructed by the doctor;
Wear protective glasses, during certain sports activities, even if several months have elapsed since the intervention;
Do not wet the eye excessively during baths and showers for at least a month;
Do not start driving again, unless otherwise instructed by your doctor;
Protect the eye with a bandage for at least a few weeks.

Risks and complications

One of the most feared complications of corneal transplantation is rejection, or the exaggerated reaction set in motion by the immune system against the "new" implanted organ. Moreover, the immune system of a specific organism is used to recognize and attack everything that is foreign to the organism itself.

Fairly common phenomenon - it actually affects one transplanted in 5 (therefore 20% of patients) - corneal rejection manifests itself with different symptoms and signs, including:

Blurring of sight;
Eye redness;
Sensitivity to light ( photophobia );
Pain in the operated eye.

In the presence of this symptom, it is advisable to contact your doctor as soon as possible to explain the problem. With a timely provision, it is possible to stop the complication evolving.

Increased risk of rejection is caused by ocular inflammations, due for example to smoky environments, irritating substances, dust or particularly windy days.

OTHER COMPLICATIONS

In addition to rejection, corneal transplantation may also involve other complications, such as:

Astigmatism;
Glaucoma;
Uveitis;
Retinal detachment;
The reappearance of the morbid condition that made transplantation necessary;
Small reopenings of surgical wounds. Remember that the repair of the cornea is very slow, so a wound against it heals very slowly;
Infections, especially when surgical wounds are healing.