Cornea - Cornea Transplantation

The cornea is the clear, transparent surface that covers the front of the eye.  Its shape and clarity help focus light on the retina (the light sensitive tissue at the back of the eye) so that we can see.  Any condition that affects the cornea and its normal clarity may result in vision impairment.

 

The cornea is a highly organized tissue, which doesn’t contain any blood vessels to nourish or protect it against infections. Instead, the cornea receives its nourishment from tears and the aqueous humor (a fluid located behind the cornea and in front of the lens).  The cornea must be clear and healthy in order to properly refract the light.

The cornea, being smooth and clear, yet strong and durable, acts as a barrier against dirt, germs and other particles that can harm the eye. The cornea is part of a larger system of protection along with the eyelids, the eye sockets, tears, and the sclera (white part of the eye).

Moreover, the cornea functions as a window that controls and focuses the light onto the retina. It is responsible for 65­-75 percent of the eye’s total focusing power.

There are conditions such as injuries, infections or chemical burns that may lead to corneal opacity and the only way to restore vision is a corneal transplantation.

In corneal transplant the damaged portion of the cornea is being replaced with a healthy donor tissue. It is a tissue transplant rather than an organ transplant (such as kidney or the entire eye).

Due to the lack of local eye banks, we obtain our corneal tissues from eye banking organizations abroad. Those organizations operate a comprehensive Quality Assurance system conforming to the highest international standards for safe tissue, and the highest ethical standards for ensuring respect and consideration of the donor's gift.  Keratoplasty remains one of the most common and safe procedures for corneal transplantation with a high success rate (approximately 95%).

PK is a full-thickness transplant procedure, in which a trephine of an appropriate diameter is used to make a full-thickness resection of the patient's cornea, followed by placement of a full-thickness donor corneal graft. The full-thickness resection may also be performed with the super-fast, super-accurate femtosecond laser, which is a bladeless laser operation.

The advantages of using a femtosecond laser in PK are the following:

  • Great precision and control in sizing of the donor and recipient corneal buttons.
  • Significant decrease in the number of stiches needed to hold the graft in place (quick and smooth healing).
  • Viability assurance.
  • Remarkable decrease in post-operative iatrogenic astigmatism.

During a corneal transplant procedure, a local anesthetic is used to numb the eye and the whole procedure is completed in about an hour. There is no need for hospitalization and usually the post-operative care includes antibiotics to prevent infection and steroids to prevent rejection.

Complications in Penetrating Keratoplasty

A graft failure usually occurs in the first year after the transplantation. In the follow-up examinations, the ophthalmologist can detect early signs of rejection and may prevent rejection by modifying and adjusting the medications.

Sometimes a corneal transplant can cause problems such us infection, inflammation, hemorrhage, increased intraocular pressure and retina detachment. These conditions are rare and most of the time manageable.

Even after a successful penetrating keratoplasty, astigmatic instability is very common, with approximately 3 to 5 degrees of regular or irregular astigmatism and can limit the quality of vision without corrective spectacles or contact lenses.  This however may be fixed.

DALK is a partial-thickness corneal transplant that involves the outer layers of the cornea. This type of transplantation is indicated for corneal scaring and keratoconus.

A DALK procedure reduces significantly the rejection rate because the host endothelium is preserved. The healing time is shorter and the Femtosecond Laser technology may be used successfully in DALK procedures as well.  For further strengthening and stabilization DALK may be combined with cross-linking in both patient’s and donor’s corneas.

Endothelial keratoplasty replaces the patient's endothelium (innermost layer of the cornea) with a transplanted disc of posterior stroma/Descemets/endothelium (DSAEK) or Descemets/endothelium (DMEK). This type of procedure is less invasive, requires one or no sutures and provides a much faster visual recovery than a full-thickness keratoplasty.

The procedure is performed under local anesthesia and it takes approximately 45 minutes. After the operation, the patient lies in a supine position, flat, facing the ceiling, for the first day to allow the retained air bubble to further stabilize the graft position. The post-operative care is shorter and includes road-spectrum antibiotics to prevent infection and steroids to prevent rejection.

The KPro treatment technique is indicated in patients with severe corneal opacity and generally when a standard transplant is unlikely to succeed.

This procedure applies to patients with severe cornea and eyelids conditions such as:

  • Stevens – Johnson Syndrome
  • Aniridia
  • Ocular burns and chemical injuries
  • Repeated corneal graft failure

Dohlman keratoprosthesis appears to be more successful than other techniques such us stem cell transplantation, which, albeit its satisfactory short term results, has a long term success rate of less than 50%.

Generally, Boston Keratoprosthesis is reasonable for patients with:

  • Previous graft failures and poor prognosis for a new keratoplasty.
  • Visual acuity less than 20/200 in the affected eye and inadequate vision in the other eye.

The keratoprosthesis is currently machined from medical grade polymethylmethacrylate (PMMA), is robust and has excellent optical properties. It consists of three components and when assembled resembles a small collar button and is implanted in the cornea. A therapeutic contact lens, which may also match the iris of the other eye, is placed to protect the surface.

This method was developed by Dr. Claes H. Dohlman, Professor of the University of Harvard, Boston whose surgical innovations in keratoplasty and keratoprosthesis have made him internationally recognized as the founder of modern corneal science. Laservision’s scientific team has closely followed and used this keratoprosthesis as Dr. Dohlman was one of Dr Kanellopoulos’ professors while he was studying in Harvard Medical School and they are still collaborating to this day.

The first keratoprosthesis procedure in Europe was performed in Athens, Greece, in 1997 with great success. The patient suffered from Ocular Cicatricial Pemphigoid that lead to blindness for many years. This technique managed to improve his vision by 8/10 from the first day, which was maintained for the rest of his life. Continued advances in design and superior postoperative care have resulted in improved outcomes and an exponential increase in the use of the device in recent years. Our pioneer scientific team is additionally combining this technique with crosslinking.

Corneal Graft Viability

Corneal graft viability is usually 10-15 years as they are rarely rejected. In keratoconus cases the probability of tissue rejection is less than 5% and increases in cases of injuries, infections or chemical burns. Post-operative care includes steroid drops for a period of 6 – 12 months. There are cases where additional medication may be required before or after the procedure.

Boston Keratoprosthesis offers long term stability and functionality, provided the rest of the ocular structures remain normal.

The treated eye may be covered with an eye pad, which the physician or the clinical personnel will remove the following day. Every patient is provided with all the necessary eye drops right after the patch removal.

Eye drops schedule

  1. Vigamox

One drop in the operative eye, four times a day for the first week.

  1. Dispersadron C

One drop in the operative eye, four times a day for as long as your physician instructs you to. It is normally required for several months.

      3. Artificial tears (Preservative-free)

One drop in the eyes, as often as needed, ten minutes after applying the medication drops. They contribute to eye moisturizing. 

If you are instructed to remove the eye patch on the same day of the procedure, then the medication drops (vigamox and dispersadron) should be used every hour. Allow a minimum of 2-3 minutes between each drop to ensure full benefit of each drop.

Eye drops Use

  • Always wash your hands before putting in the drops.
  • Shake the bottles thoroughly prior to each drop .
  • There is no preference as to which medication drop is applied first, just remember to wait 2-3 minutes between each drop.
  • You may experience a medicinal taste in the back of your throat after putting in drops, this is normal.
  • Eye drops are not applied during night time.
  • Be careful not to touch the eye with the bottle.
  • Keep eye drops in a cool place, away from heat, moisture and direct sunlight

Precautions

  • It is very important to pay attention to your eyes hygiene for ten days after the operation.
  • It is normal to experience discomfort, burning sensation and grittiness the first few hours. You may use any over-the-counter medication (Depon, Panadol, Ponstan, etc. Except aspirin).
  • Refrain from rubbing, bumping, or scratching your eyes.
  • A pair of eye shields is provided in your “post-operative care kit”. The shields are to be worn at night or during naps with the pointed part of the shield pointing towards the nose. A roll of tape is included in the kit to apply the shield for subsequent nights.
  • Do not swim/ work out for 10 days after the operation.
  • Do not rinse your eyes with water. Wash your hair leaning backwards keeping your eyes closed like being at hairdresser’s.
  • Avoid facial cosmetics, makeup, mascara and colored contact lenses for 10 days after the operation.
  • Do not drive until you are confident with your vision.
  • You can resume most normal activities (reading, watching TV, working in front of a computer screen) from the next day of the procedure.

After the operation, the patient should lie in a supine position, flat, facing the ceiling, for the first day to allow the retained air bubble to further stabilize the graft position.

The treated eye may be covered with an eye pad, which the physician or the clinical personnel will remove the following day. Every patient is provided with all the necessary eye drops right after the patch removal.

Eye drops schedule

  1. Vigamox

One drop in the operative eye, four times a day for the first week.

  1. Dispersadron C

One drop in the operative eye, four times a day for as long as your physician instructs you to. It is normally required for several months.

      3. Artificial tears (Preservative-free)

One drop in the eyes, as often as needed, ten minutes after applying the medication drops. They contribute to eye moisturizing. 

If you are instructed to remove the eye patch on the same day of the procedure, then the medication drops (vigamox and dispersadron) should be used every hour. Allow a minimum of 2-3 minutes between each drop to ensure full benefit of each drop.

Eye drops Use

  • Always wash your hands before putting in the drops.
  • Shake the bottles thoroughly prior to each drop .
  • There is no preference as to which medication drop is applied first, just remember to wait 2-3 minutes between each drop.
  • You may experience a medicinal taste in the back of your throat after putting in drops, this is normal.
  • Eye drops are not applied during night time.
  • Be careful not to touch the eye with the bottle.
  • Keep eye drops in a cool place, away from heat, moisture and direct sunlight

Precautions

  • It is very important to pay attention to your eyes hygiene for ten days after the operation.
  • It is normal to experience discomfort, burning sensation and grittiness the first few hours. You may use any over-the-counter medication (Depon, Panadol, Ponstan, etc. Except aspirin).
  • Refrain from rubbing, bumping, or scratching your eyes.
  • A pair of eye shields is provided in your “post-operative care kit”. The shields are to be worn at night or during naps with the pointed part of the shield pointing towards the nose. A roll of tape is included in the kit to apply the shield for subsequent nights.
  • Do not swim/ work out for 10 days after the operation.
  • Do not rinse your eyes with water. Wash your hair leaning backwards keeping your eyes closed like being at hairdresser’s.
  • Avoid facial cosmetics, makeup, mascara and colored contact lenses for 10 days after the operation.
  • Do not drive until you are confident with your vision.
  • You can resume most normal activities (reading, watching TV, working in front of a computer screen) from the next day of the procedure.
  • You should not fly until your surgeon confirms you are allowed to.