Corneal transplant

A corneal transplant or keratoplasty is a surgical procedure to replace the diseased or damaged cornea with a healthy donated cornea (permission is given by the donor before death or, more commonly, by the family).

The cornea is a clear, dome-shaped front portion of the eye. It consists of three main layers and two thin layers between them. Cornea prevents the entry of germs, dirt, damaging ultraviolet (UV) light, and other particles into the eye. It also helps to focus the light that enters the eye and makes the vision clear.

If the cornea gets damaged, it may change its shape or become cloudy and opaque. This may lead to blindness. 

The cornea consists of five layers of cells. The outermost layer is the epithelium that acts as the main barrier to protect the eye. The epithelium is followed by a layer of tough tissue called Bowman’s layer, which helps give cornea it's unique shape. The Bowman’s layer is followed by stroma, Descemet’s membrane (DM), and the innermost layer known as the endothelium. Stroma contributes to about 95% of the total corneal thickness. Descemet’s membrane is the strongest layer in the cornea. The innermost endothelial layer consists of a single cell layer that maintains transparency or clarity of the cornea.

Based on the layers of the cornea that are damaged and replaced, the surgeon will recommend one of the following types of keratoplasty:

• Penetrating keratoplasty: Entire cornea
• Anterior lamellar keratoplasty: This type of keratoplasty consists of the following subtypes with each listing the layer to be removed:
  • Bowman’s layer transplant: Bowman’s layer
  • Superficial anterior lamellar keratoplasty: Superficial layers of the stroma
  • Deep anterior lamellar keratoplasty: Stroma
• Posterior lamellar keratoplasty/endothelial keratoplasty: The type can be further divided into the following subtypes:
  • Descemet’s membrane  endothelial keratoplasty: Endothelium and DM (replaced by donor endothelium and DM)
  • Descemet’s stripping endothelial keratoplasty: Endothelium and DM (replaced by donor DM and endothelium and inner layers of stroma)

Keratoprosthesis is a type of keratoplasty that replaces the entire cornea with an artificial implant.

This surgery is recommended to correct vision problems and provide relief from eye pain associated with various eye diseases or conditions. The indications for which the surgeon may recommend the different types of keratoplasty are as follows:

• Penetrating keratoplasty:

  • Ectasias
  • Keratoconus (thinning and bulging of cornea in the shape of a cone)
  • Dystrophies
  • Corneal degeneration
  • Congenital opacities
  • Non-infectious, microbial, or viral keratitis
  • Scarring after infectious keratitis
  • Mechanical or chemical injury
  • Regrafts
• Bowman’s layer transplant:
  • Keratoconus
  • Persistent subepithelial haze (post excimer laser surface ablation)
• Superficial anterior lamellar keratoplasty: Opacification or scarring in the superficial layers of stroma due to:
  • Infection
  • Trauma
  • Inflammation
  • Stromal dystrophy (a congenital condition in which the cornea starts to appear hazy)
  • Previous refractive procedures and other surgeries
• Endothelial keratoplasty:
  • Endothelial failure (compromised endothelial function) post PK
  • Congenital hereditary endothelial dystrophy (wasting away of the endothelium)
  • Fuchs’ endothelial dystrophy
  • Posterior polymorphous dystrophy
  • Bullous keratopathy (aphakic and pseudophakic); a condition characterised by the formation of small vesicles inside the cornea 
  • Endothelial decompensation (gradual loss of endothelial cell function) due to previous intraocular surgery

Keratoprosthesis is performed when conventional keratoplasty procedure proves to be ineffective. It is recommended in the following conditions:  

• End-stage eye diseases such as:
  • Severe Stevens-Johnson syndrome
  • Ocular cicatricial pemphigoid (an autoimmune condition that leads to conjunctival scarring)
  • Trachoma
• Chemical injury
• Severe dry eye
• Uncorrectable loss of eyelid

Contraindications for corneal transplant surgery are region-dependent (vary in different countries). In some countries, a corneal transplant is contraindicated if it is possible that the procedure will not restore the integrity or function of the cornea.

Before performing the surgery, the following preparation is required:

• Your doctor will perform certain tests, including an eye examination to check if you are an eligible candidate for surgery.
• The surgeon will ask you to share a list of all the medicines that you take, including over-the-counter medications, supplements, and herbs. 
• You may need to stop blood-thinning medicines (ibuprofen, aspirin, and warfarin for example) for 10 days before the surgery. 
• If you take medicines like water pills, insulin, or diabetes medicines regularly, ask your doctor if you can take them on the morning of the surgery. 
• You will need to fast after midnight the night before the surgery. 
• Avoid drinking alcohol a day before and after the surgery. 
• On the day of the procedure, do not wear jewellery or apply creams, lotions, or makeup around your eyes or on the face.
• Ask a friend, family member or a responsible adult to drive you home after the surgery.
• If you agree to undergo this surgery, you will be asked to sign a consent form.

After your admission to the hospital on the scheduled day of surgery, the hospital staff will ask you to wear a hospital gown. The surgery usually includes the following steps:

• Your doctor will put some eye drops in your eyes and give you medicine so that you can relax.
• He/she will give you local anaesthesia around your eye to numb the eye and prevent eye movement during surgery. You will be awake during your surgery.
• A device will be placed on your eye to keep it open. However, due to the anaesthesia, you may not be able to see anything.
• The surgeon will examine and process the donated cornea of the deceased person to make sure it is suitable for your surgery.
• He/she will use a small circular blade to remove your entire cornea or just the damaged layers.
• Thereafter, the surgeon will use stitches to fix the donor cornea in position. In some types of keratoplasty, surgeons use an air bubble instead of stitches to position the donor cornea.

The type of keratoplasty depends on the damaged corneal part, and how much of the cornea needs to be replaced. The following techniques can be used to perform a keratoplasty:

• Penetrating keratoplasty (PK): The entire damaged cornea is removed using a small circular blade. It is then replaced with a healthy donated cornea that is stitched into place.
• Endothelial keratoplasty (EK): The innermost layer of the cornea is replaced with a new inner layer of the cornea from the donor. The doctor will use an air bubble instead of stitches to position the donated cornea properly.
• Deep anterior lamellar keratoplasty (DALK): The outer layers of the cornea are replaced with new ones, the innermost layer is left as such. 

During this surgery, your eye doctor may also repair other eye problems like cataract (clouding of the lens of the eye). He/she will place an eye shield or patch over your eye to cover it for safety.

A cataract transplant takes one to two hours to complete. After the surgery, the doctor or a nurse will check you to see if you have recovered from the anaesthesia. You will be able to go home on the same day of your surgery.

It may take approximately a year to completely recover from the surgery. You may need to take the following care at home:

• Use eye drops and painkillers as prescribed by your doctor.
• After endothelial keratoplasty, you will need to keep your face up, that is, lie on your back for a few days after the surgery. This helps the replaced tissue to stay in position.
• Avoid driving unless advised by the doctor.
• Do not perform activities that will put pressure on your eyes.
• Avoid lifting heavy objects.
• Avoid exposure to dust, smoke, or blowing sand.
• Wear a protective eye shield or glasses.
• Avoid rubbing or pressing on your eyes.
• Ask your surgeon before resuming all your daily activities.
• Close your eyes when you shower. 
• Avoid swimming and hot tubs for three months.
• You may be able to return to work after two weeks of rest.

When to see the doctor?

Contact the surgeon at the earliest if you notice the following symptoms:

• Excessive redness and pain in the eye
• Increased sensitivity to light 
• Vision problems

The following are some risks of corneal transplant surgery:

• Retinal detachment
• Cataracts
• Inflammation of the eye
• Severe infection on the surface of the eye (ulcer or abscess of the eye) or inside the eye (Endophthalmitis) 
• Onset of or worsening of glaucoma
• Detachment of the new cornea
• Refractive errors (leading to the inability to see clearly)
• Bleeding in the eye

You will need to follow up with your doctor within a day or two of the surgery. During the follow-up, your doctor will check the healing of your eye. The stitches may be removed a few months after surgery. You will be recommended to get your vision checked regularly to see if you need glasses.

Disclaimer: The above information is provided purely from an educational point of view and is in no way a substitute for medical advice by a qualified doctor.