PDEK

introduction

What is PDEK?

Pre Descemet’s Endothelial Keratoplasty is a partial thickness corneal transplant. The diseased endothelial cells are removed from the patient’s eye and selectively replaced with a new layer of endothelial cells which are taken from the donated eye. The endothelial cells are the healthy cells lining the back of the cornea which pump fluid from the cornea to prevent the cornea swelling. The normal endothelial count is 2000 – 3000 cells/mm2. When the cells decrease in number < 500 cells/mm2, corneal decompensation occurs, clarity of the cornea reduces and eventually the vision becomes cloudy.

How is the penetrating keratoplasty surgery performed?

The penetrating keratoplasty surgery is usually performed under local anaesthesia. Through a small corneal incision (opening), the endothelium is removed from the patient’s eye and a disc of donor endothelium is inserted in the patient’s eye which is placed in position with the help of an air bubble.

A few stitches may be taken which will be removed 3-4 weeks after the surgery. Once keratoplasty surgery is over, the patient needs to lie down flat for a few hours for proper attachment of the graft. The air bubble usually gets absorbed in 48 hours but may take longer. 

What are the indications of Penetrating Keratoplasty (PDEK)?

  • Fuch’s endothelial dystrophy
  • Pseudophakic bullous keratopathy
  • Aphakic bullous keratopathy
  • ICE syndrome
  • Endothelial dysfunction secondary to glaucoma

What are the advantages over full thickness penetrating Keratoplasty?

  • Few sutures required as compared to penetrating keratoplasty.
  • Suture induced astigmatism is avoided
  • Suture related complications are avoided
  • Greater stability
  • Faster visual rehabilitation
  • The graft can be obtained from any age group of the donated eyes
  • Chances of rejection are less

 

What are the complications of Penetrating Keratoplasty (PDEK)?

  • Graft detachment/ dislocation
  • Recurrent epithelial erosions
  • Cataract formation
  • Glaucoma
  • Graft rejection
  • Graft failure 

What is corneal graft rejection?

The donor eye is genetically different from the patient’s body, due to which the patient’s body tries to fight against it. This is called corneal graft rejection.  

What are the symptoms of corneal graft rejection?

The symptoms are: Redness, Sensitivity to light, Vision drop, Pain (RSVP). Along with sticky discharge and foreign body sensation.

Report to your Ophthalmologist as soon as possible if any of the above symptoms show up post-surgery.


How do I prevent graft rejection?

  • In order to prevent rejection, a list of anti-rejection medications will be prescribed by your doctor, which should be used religiously.
  • You should have an adequate supply of eyedropsat home so that a single dose is not missed.
  • Do not stop any medication without consulting your Ophthalmologist.
  • In case any of the above symptoms of rejection occur, meet your Ophthalmologist immediately. It can often be reversed if anti-rejection medications are started promptly. It should also be noted that rejection can occur at anytime in the years to come.
  • Review regularly to check for vision, intraocular pressure, graft condition and retinal assessment.

 

What are the risk factors for rejection?

  • Vascularisation over the cornea
  • Pre-existing inflammation
  • Corneal transplantdone more than 2 times
  • Pre-existing glaucoma

What is graft failure?

When the corneal graft rejection has not been promptly treated or does not respond to anti- rejection medication, graft failure has occurred. The only way of managing graft failure is by replacing the graft. In addition, there are three types of graft rejection: acute, hyperacute, and chronic rejection.

Written by:Dr. Preethi Naveen – Training Committee Chair – Dr. Agarwals Clinical Board

FAQ

What are the three types of graft rejection?

As mentioned above, there are three types of graft rejection:

When the antigens are entirely mismatched, hyperacute rejection begins a few minutes after the donation. In order to ensure that the patient does not have to suffer, the tissue must be removed as soon as possible.  When in many cases, when the receiver receives the wrong type of blood, they might experience this sort of rejection. For instance, when a person with type B blood is given type A blood.

Next type of graft rejection is called acute rejection which can happen anywhere between the first week and three months after the transplant. It is imperative to keep in mind that acute rejection affects all recipients in one or the other way.

Now, let’s delve into the last type of graft rejection: chronic rejection. This can occur over a long period of time. The body’s continual immunological response to the new organ causes the transplanted tissues or organ to deteriorate over time.

 

In medical terms, graft refection is a very common mechanism. It occurs when the immune system of the recipient attacks the organ or the tissue of the receiver and slowly begins to destroy it. Fundamentally, the idea behind the mechanism of graft rejection is the presence of the donor’s own unique set of HLA proteins, which the recipient’s immune system recognises as alien, frequently triggers this immunological response.

On the other hand, histocompatibility refers to the degree of similarity between the recipient and the donor’s HLA genes. Simply put, the more genetically compatible the recipient and the donor are, the more tolerant the recipient’s immune system should be of the entire transplant process.

In organ/tissue transplants, there will always be some degree of rejection, unless the donor and the receiver are genetically identical, for example, in cases of identical twins.

 

In some situations, a patient may suffer from a graft versus host reaction, in which already matured immune cells present in the donor graft begin attacking the recipient’s healthy cells. Graft against host reaction, which occurs when the donor graft is classified as “immune-competent” (i.e., capable of eliciting an immunological response), is a risk associated with bone marrow transplants or stem cell transplants. In addition, it can also occur after blood transfusions.

Penetrating keratoplasty is an outpatient procedure, which means that patients can return home the same day. The majority of patients will have a post-operative appointment the next day.

Patients are given prescription eye drops to use in the weeks and months following a corneal transplant to aid in the healing process. Patients may experience blurry vision after the treatment while the eye adjusts to the new cornea. While recovery times differ, most patients report that their eyes heal, and their eyesight improves within a few months of surgery.

It is critical to safeguard the eye as much as possible in the days following the treatment. During this time, your doctor may advise you to wear a protective shield.

Although the corneal replacement may have been executed successfully and is working as well as it can, various eye disorders may affect the quality of a person’s eyesight after the corneal replacement surgery.

To improve vision, the new cornea may carry some level of astigmatism, which in many cases, requires special contacts or glasses. Other eye illnesses including glaucoma, diabetic retinopathy, or macular degeneration might reduce the patient’s vision quality and restrict them from seeing 20/20.

 

You will have to go through the following procedures before your cornea or eye transplant surgery:

  • A comprehensive eye examination is required. Your eye doctor thoroughly examines you for any eye diseases or conditions that could lead to and complications or issues following the eye transplant surgery.
  • Your eye’s measurements. The concerned ophthalmologist   will determine the exact size of the cornea that you’ll require in the eye transplant surgery.
  • A close review of all of the drugs and supplements you’re consuming. Before or after your cornea/eye transplant, you may need to stop using certain drugs or supplements.

Once the penetrating keratoplasty surgery is successful, you may drive after the anaesthesia has come off and the vision in the other eye is completely fit for driving. 

It could take up to 24 hours for this to happen. However, it’s possible that your surgeon will advise you to wait a few days before stepping behind the wheel. Remember that you’ll need someone to drive you home from the hospital and drive you back the next day for your follow-up appointment.

 

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