About the CorneaIn order to perform these very important functions, the cornea must have a regular shape (for sharp focusing) and must be clear (transparent) for functioning as a window. The cornea is about 12 mm in diameter, and 0.50 mm in thickness in the centre, but if the cornea becomes opaque this would result in the patient becoming functionally blind since light will not be able to get through the eye. The same happens if the cornea shape becomes irregular and does not allow sharp focussing such as in keratoconus. Most diseases can be treated medically or with the help of contact lenses but in some cases corneal transplantation may be needed. Corneal transplantation refers to the replacement of all of part of the cornea with a donor cornea.
When is Treatment Required?In general, corneal transplantation is required for optical, tectonic or therapeutic reasons. Optical reasons include opacification of the cornea (for instance after a severe corneal infection a corneal dense opaque scar can develop thus impairing vision), thickening of the cornea (such as in Fuchs corneal endothelial dystrophy) and shape changes (for instance in keratoconus where the cornea becomes thin and bulges forward not allowing proper focusing). Tectonic reasons are associated with the loss of integrity of the cornea such as corneal perforation (post-trauma, infective or degenerative) where a corneal transplant is needed to patch up and close the cornea. Therapeutic reasons are usually severe infection, which did not respond to medical treatment and as a result of continued worsening, a corneal transplant is required to replace the diseased cornea and save the eye. Cosmetic reasons when there is poor visual potential and an unsightly corneal scar damaging the cosmetic appearance of the eye The cornea is 0.5mm thick in the centre, and the main functional layers are the ‘epithelium’, the ‘stroma’ and the ‘endothelium’. The ‘epithelium’ is the first and foremost layer of the cornea and represents the skin of the cornea. The middle layer, the ‘stroma’ forms the majority of the corneal thickness and needs to be kept in a dehydrated state to maintain transparency. It is also the layer that tends to develop scarring if damaged. The innermost layer is the ‘endothelium’, which is very important for maintaining dehydration and transparency of the rest of the cornea. Corneal transplantation may now be performed to replace the whole cornea or the diseased layers only.
Advanced Corneal Transplant Surgery Types
This type of operation refers to corneal transplant where the outer/front part of the cornea is replaced. It is performed when the posterior part of the cornea, the “endothelium” is healthy and the disease is confined to the front layers of the cornea. It is usually performed in keratoconus.
The advantages compared with full thickness transplant (removal of the whole cornea) are:
1. less risk of rejection
2.longer graft survival
3.Stronger eye wall
The recovery process for DALK is similar to penetrating keratoplasty (PKP = full thickness where the full cornea is removed and replaced) but the stitches can come out sooner and hence recovery of vision can be faster. The operation is performed under general or local anaesthetic and takes about one hour. A central 8-9mm button of the patient’s cornea is removed and a similar-sized button of the donor cornea is sewn in with tiny stitches. These cannot be felt nor seen. Patients can go home after the operation the same day.
Anterior Lamellar Keratoplasty, only the outer layer of the cornea are transplanted because diseased (for instance in keratoconus)
Usual follow-up after surgery takes place at day one, week one and thereafter month 3, 6 and 12. We generally recommend that you take 1-2 weeks off work. You will need to use steroid anti-rejection eye drops for at least 6 months and in some cases longer. Stitches are usually removed after 6-12 months for surgery. The vision is variable during this period and final vision outcome can only be reached when when stitches are fully removed. Patients are assessed for glasses or contact lenses and in some cases can undergo further procedures including laser eye surgery and implantable contact lens surgery to further improve the visual outcome.
This type of surgery is used when only the thin back layer of the cornea is affected (like in Fuchs corneal endothelial dystrophy) and hence only this back layer is removed and transplanted. EK is a revolutionary new procedure for diseases affecting the endothelial innermost layer of the cornea. This is a very thin layer of about 10-20 microns that functions has a porous membrane and keep water out of the cornea. When the endothelial layer is damaged the cornea become waterlogged and therefore thicker and opaque. EK is the best and only procedure advisable in patients with disease limited to the back of the cornea (such as Fuchs endothelial dystrophy and pseudophakic bollous keratopathy). It entails the removal of the diseased back layer (the endothelium) leaving intact the thick outer layers of the cornea.
The advantages are:
- The surgery is performed through keyhole corneal incisions similar to those used in cataract surgery, the visual recovery is faster, the risk of rejection is less and preserves the structural integrity of the eye.
- The operation is also faster and is always done under local anaesthesia.
The patients’ endothelium is removed through a small incision and a 8.5mm disc of donor endothelium is inserted and pressed into position against the back of the patient’s cornea using a bubble of air. Posturing, that is lying flat for a few hours, is needed to help the adhesion of the donor material and usually no stitches are required. A review is needed the day after the surgery and at week 1, and 1-3-12 months. We generally recommend that you take 1 week off work. Patients will need to use anti-rejection steroids eye drops for 1-2 years.
Posterior Lamellar Keratoplasty, only the inner layer of the cornea are transplanted because diseased (for instance in Fuchs corneal endothelial dystrophy).
,The femtosecond laser (FSL) is a near-infrared laser that is successfully used to create precise lamellar flap in Femto LASIK vision correction but can also be used in modern corneal transplant surgery. Rather than preparing the corneal transplant graft with a traditional trephine (a specialized circular blade) as in standard transplantation techniques, both the patient and the recipient cornea are fashioned with the femtosecond laser. This allows the construction of customised graft shape for both donor and recipient The femtosecond laser can be used to customise graft shape for both full thickness corneal graft (PKP) and Partial thickness anterior lamellar graft (DALK).
This procedure can potentially give the following benefits:
- Enhance wound stability
- Faster and strong healing
- Corneal irregularity and astigmatism reduced
- Reduce number of sutures and suture tension, thus allowing earlier removal of the sutures
Vincenzo Maurino has extensive experience is a pioneer and world-class expert of femtosecond laser assisted corneal graft surgery. He has been invited to several international meetings to present his work on femtosecond laser corneal graft surgery which has also been published in peer reviewed ophthalmic journals.
Femtosecond laser mushroom configuration corneal transplant donor and recipient. On the right eye 12 months after femtosecond laser mushroom shaped corneal transplant for keratoconus.
Laser assisted corneal transplants are performed in two stages. In the first, the patient undergoes the femtosecond laser-assisted pre-cut procedure in the laser room. This procedure is done under anaesthetic drops and takes approximately 40 seconds. The patient is then transported to the operating room, for the main surgery performed under general or local anaesthetic for the conclusion of the transplant procedure. The operation takes about one hour. A central 8.5mm button of the patient’s cornea is removed and a similar-sized button of the donor cornea, previously cut with femtosecond laser, is stitched in with tiny stitches. These cannot be felt or seen. Risks and visual recovery are similar to DALK and PKP.
This type of surgery is used for the replacement of the whole cornea. It is usually performed under general anaesthetic and involves the removal of a full thickness disc of 8.5 mm of the cornea of the patients and suturing of a corneal disc from a donor of the same dimensions.
PKP is only performed when there is advanced corneal disease and all corneal layers are affected. The operation is performed usually under general anaesthetic and takes about one hour. A central 8.5mm button of the patient’s cornea is removed and a similar-sized button of the donor cornea is sewn in with tiny stitches. These cannot be felt or seen. Patients can go home after the operation the same day. Usual follow-up after surgery takes place at day one, week one and thereafter month 3, 6 and 12.
It is generally recommended that you take 2 weeks off work. You will need to use steroid anti-rejection eye drops for at least 12 months and in some cases longer. Stitches are usually removed after 18 months after PKP. Vision is variable during this period and the final vision outcome can only be achieved when the stitches are fully removed. Patients are assessed for glasses or contact lenses and in some cases can undergo further procedures including laser eye surgery and implantable contact lens surgery to further ameliorate the outcome.
Like in any eye surgery there are risks in corneal transplant surgery. Sight loss is possible but fortunately rare with corneal transplant surgery.
Rare but serious complications include:
- Sight-threatening infection
- Severe haemorrhage causing loss of vision
- Retinal detachment.
Corneal transplant rejection occurs when the patient’s immune system is attacked. Corneal Transplant Rejection can often be reversed if anti-rejection medication is started promptly.
Graft Failure happens when the cornea becomes cloudy again and vision becomes blurred. It is less common in DALK and EK compared with PKP.
Glaucoma can usually be controlled by eye drops but occasionally requires surgery.
Cataract can be removed if vision is affected.
Ultimately patients need to be fully aware of the possibility of sight loss albeit rare before deciding to undergo any type of corneal graft surgery. At the consultation Vincenzo Maurino will explain the type of corneal graft most suited for you, its generic and specific risks and benefits. Vincenzo is a talented eye surgeon and corneal graft surgeon and has taught corneal surgery to international fellows for the last 15 years.
Why choose Mr Maurino at Moorfields?
Vincenzo Maurino main research focus is in the advancement of surgical technique and technologies, especially femtosecond laser technology for corneal transplant and cataract surgery. He is a Consultant Ophthalmic Surgeon specialising in Laser Vision Surgery & Corneal Transplant at Moorfields Eye Hospital and Visiting Professor of Corneal Transplant Surgery at University of Rome. Having performed over 30,000 surgical procedures, he is one of Moorfields best eye surgeons who can advise on best choice of eye surgery after a comprehensive assessment of your eye conditions, eye health and lifestyle.