Corneal transplant surgery
This is a surgical operation in which the affected corneal tissue is surgically removed and replaced with donor corneal tissue from a deceased person. Depending on the condition, your surgeon may transplant the entire cornea (Penetrating Keratoplasty) or only certain layers of the cornea ; Deep Anterior Lamellar Keratoplasty (DALK), Descemet stripping automated endothelial Keratoplasty (DSAEK) or Descemet’s membrane endothelial keratoplasty (DMEK). Corneal transplant surgery is a significant eye procedure, and achieving good vision after a transplantation may take some time. In Penetrating Keratoplasty and deep anterior lamellar keratoplasty, fine sutures remain in the cornea for 12-18 months following the surgery. After removal of the sutures, it is common for patients to require spectacles, contact lenses or additional surgery for best vision.
Keratoconus is a condition affecting the cornea (the clear window of the front of the eye). It results in thinning and stretching (also called “ectasia”) of the cornea. In most individuals, the condition begins in the teenage years and generally progresses until patients are in their thirties. Rarely the condition can begin in childhood. A similar condition, pellucid degeneration (PMD) may occur in older patients.
It is not known exactly what causes keratoconus. Patients with the condition may have a family history of the condition, but not always. There are probably some genetic factors that result in a weakening of the corneal structure. Keratoconus is also more likely with frequent eye rubbing, and patients should avoid rubbing their eyes altogether as this can worsen the condition.
The condition is often undetected for a long period. In its earliest stages, patients notice mild blurred vision, and may be sensitive to glare. Many patients are initially diagnosed with astigmatism and prescribed spectacles for astigmatism. Eye care professionals may first recognise keratoconus when there is progressive worsening of astigmatism and it may become impossible to improve vision adequately with glasses alone.
Other signs of the condition are often visible on close examination of the patient’s cornea during an eye exam. Further confirmation is often with a keratometer or topographer with both measure the curvature and shape of the cornea.
Generally, keratoconus is slowly progressive, however especially in younger patients, there can be rapid worsening that requires early treatment.
Modern management of keratoconus involves two main goals. The first aims to prevent further worsening of the shape of the cornea. Typically, this involves a procedure to stabilize and prevent stretching of the corneal collagen (known as corneal collagen crosslinking, CXL). The second aim of treatment is to improve the focus of the eye for clear and satisfactory vision.
1. Corneal Collagen Crosslinking
Where keratoconus is still worsening, cross linking helps to prevent further deterioration. It is performed as a day procedure typically over 20-40 minutes. The procedure involves gently removing the surface layer (“epithelial” cells) of the cornea. Eyedrops containing a vitamin called Riboflavin (Vitamin B2) are then applied for 20 minutes. Riboflavin is absorbed by the corneal collagen tissue. Once the cornea has been pre-treated with riboflavin, ultraviolet light is used for the crosslinking treatment. Research suggest that the ultraviolet light activates the riboflavin, creating connections between the long collagen molecules which prevents the collagen from stretching further.
Many patients with mild keratoconus can achieve excellent vision with glasses alone.
3. Contact Lenses
When glasses are no longer adequate to provide a clear image, contact lenses (usually rigid contact lenses) are often the next step. Rigid contact lenses come in many shapes, sizes and designs, and a specialist in fitting contact lenses will help patients to decide on the best options for them. There is frequently a period of adjustment to wearing contact lenses, and they may be uncomfortable in the early stages. With time, this typically improves.
4. Intrastromal Ring Segments
Ring segments are a novel surgical procedure involving insertion of very small crescent shaped plastic inserts within the substance of the cornea. The ring segments may improve vision by improving the shape of the central cornea. The procedure is frequently combined with corneal collagen crosslinking as the ring segments themselves do not prevent ongoing progression of the condition.
5. Corneal Transplantation
Because keratoconus tends to worsen over time, some patients ultimately require corneal transplantation for good vision. This is a surgical operation in which the affected corneal tissue is surgically removed and replaced with donor corneal tissue from a deceased person. Corneal transplant surgery is a significant eye procedure, and achieving good vision after a transplantation may take some time. Fine sutures remain in the cornea for 12-18 months following the surgery. After removal of the sutures, it is common for patients to require spectacles, contact lenses or additional surgery for best vision. In suitable patients, transplantation can be life changing and offers a real solution for patients with more severe keratoconus.