The National Institute for Health and Clinical Excellence (NICE) issued full guidance to the NHS in England, Wales, Scotland and Northern Ireland on insertion of hydrogel keratoprosthesis in June 2004. In accordance with the Interventional Procedures Programme Process Guide, guidance on procedures with special arrangements are reviewed 3 years after publication and the procedure is reassessed if important new evidence is available.
The guidance was considered for reassessment in June 2007 and it was concluded that NICE will not be updating this guidance at this stage. However, if you believe there is new evidence which should warrant a review of our guidance, please contact us via the email address below.
The cornea is the transparent part of the coating of the eyeball, which covers the iris and pupil and admits light to the interior of the eye. Injury or disease can make the cornea opaque, hindering the passage of light and resulting in loss of vision. Diseases that can cause the cornea to deteriorate include keratoconus, bullous keratopathy and herpetic eye disease.
A corneal transplant is the standard treatment when the cornea becomes damaged by injury or disease. This procedure involves the removal of a disc comprising the majority of the cornea using a trephine and replacing it with a corresponding disc from the cornea of a donor eye. In penetrating keratoplasty, the disc removed is the entire thickness of the cornea and so is the replacement disc. Some patients can not undergo the standard procedure using donor tissue for several reasons, such as disease severity, severe involvement of the conjunctivae objection to the use of donor tissue, failed past donor tissue transplants, or when measures required to prevent graft rejection are medically contraindicated. For these patients, penetrating keratoplasty using an artificial cornea or keratoprosthesis is an option.
The implantation of a synthetic hydrogel cornea is a two-stage surgical procedure. The first stage involves making a 270 degree partial thickness incision at the junction of the cornea and sclera, to allow an intralamellar pocket to be created within the cornea. The superficial flap is then reflected to allow a portion of the central part of the posterior lamella to be removed using a trephine, and the synthetic hydrogel cornea to be inserted into the intralamellar pocket. The superficial flap is repositioned and the incision closed. In most cases, the operation is completed by forming a flap of tissue from the conjunctiva (the outer layer of the 'white' of the eye), which is used to cover the surface of the front of the eye. This may cause changes in the cosmetic appearance of the eye.
The second stage of the procedure is performed 12 weeks later, and involves removing the conjunctival cover and the superficial flap of the cornea exposing the synthetic hydrogel cornea to light. The eye may still not appear completely 'normal' after this stage of the operation.