Keratoprosthesis
Encyclopedia
Keratoprosthesis is a surgical procedure where a severely damaged or diseased cornea
is replaced with an artificial cornea. While conventional cornea transplant uses donor tissue for transplant, an artificial cornea is used in the Keratoprosthesis procedure. The surgery is performed to restore vision in patients suffering from severely damaged cornea due to congenital birth defects, infections, injuries and burns.
Keratoprotheses are made of clear plastic with excellent tissue tolerance and optical properties. They vary in design, size and even the implantation techniques may differ across different treatment centers. The procedure is done by ophthalmologists, often on an outpatient basis.
The idea of artificial cornea was first proposed in 1789 by French ophthalmologist Guillaume Pellier de Quengsy .
, Osteo-Odonto-Keratoprosthesis
(OOKP) and AlphaCor.
form. The doctor may also perform physical and lab examinations, such as an X-ray
, an EKG, a slit lamp test, an ultrasound B-scan, or an A-scan.
The surgery date and time is also set, and the patient will also be told where the surgery will take place. The patient can also make any other queries regarding the procedure.
is given before the surgery begins.
An eyelid speculum
is used to keep the eye open throughout the surgery. Some lubrication may be used to prevent the eye from drying. An incision is made at the junction of the cornea and sclera
. An intralamellar pocket is created within the cornea. The artificial cornea is then inserted into the intralamellar pocket. The flap is then repositioned and the incision is closed.
Typically, there is a follow up session few days after surgery, when patients’ complaints are addressed and modifications are made, if needed.
Since Keratoprosthesis is a fairly rare surgical procedure, constant attempts are being made to improve the outcome of the surgery. Also, the material and design used in the artificial cornea may vary and as a result of this, there can be minor variations in surgical procedure as well.
The surgery is done on an outpatient basis with the patient returning home the same day.
and Singapore
where the cost of treatment may be as little as one fourth the cost as in the US or UK.
Cornea
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Together with the lens, the cornea refracts light, with the cornea accounting for approximately two-thirds of the eye's total optical power. In humans, the refractive power of the cornea is...
is replaced with an artificial cornea. While conventional cornea transplant uses donor tissue for transplant, an artificial cornea is used in the Keratoprosthesis procedure. The surgery is performed to restore vision in patients suffering from severely damaged cornea due to congenital birth defects, infections, injuries and burns.
Keratoprotheses are made of clear plastic with excellent tissue tolerance and optical properties. They vary in design, size and even the implantation techniques may differ across different treatment centers. The procedure is done by ophthalmologists, often on an outpatient basis.
The idea of artificial cornea was first proposed in 1789 by French ophthalmologist Guillaume Pellier de Quengsy .
Types
Although many keratoprostheses have been developed only three are used commonly including the Boston keratoprosthesisBoston keratoprosthesis
The Boston Keratoprosthesis is a collar button design keratoprosthesis or artificial cornea. It is composed of a front plate with a stem, which houses the optical portion of the device, a back plate and a titanium locking c-ring. It is available in type I and type II formats...
, Osteo-Odonto-Keratoprosthesis
Osteo-Odonto-Keratoprosthesis
Osteo-odonto-keratoprosthesis is a medical procedure to restore vision in the most severe cases of corneal and ocular surface patients. It includes removal of a tooth from the patient or a donor. After this, a lamina of tissue cut from the tooth is drilled and the hole is fitted with optics...
(OOKP) and AlphaCor.
Indications
Indications of keratoprotheses include the following:- Treatment of patients whose vision is less than 20/400 in the affected eye.
- Patients with failed corneal transplant using donor cornea and have little or no vision left.
- Patients with non-autoimmune diseases, congenital birth defects and other ocular problems.
Pre-operative examination
In most cases, the patient meets the ophthalmologist for eye examination and other tests weeks or months preceding surgery. During the meeting, the ophthalmologist will examine the eye and diagnose its condition. The doctor will also record the history of the patient’s health and other previous eye treatments, if any. The doctor will discuss the risks and benefits of the surgery. If the patient elects for the surgery, the doctor will have the patient sign an informed consentInformed consent
Informed consent is a phrase often used in law to indicate that the consent a person gives meets certain minimum standards. As a literal matter, in the absence of fraud, it is redundant. An informed consent can be said to have been given based upon a clear appreciation and understanding of the...
form. The doctor may also perform physical and lab examinations, such as an X-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
, an EKG, a slit lamp test, an ultrasound B-scan, or an A-scan.
The surgery date and time is also set, and the patient will also be told where the surgery will take place. The patient can also make any other queries regarding the procedure.
Patient selection
- Vision should not be better than 20/400.
- Blink and tear mechanisms should be reasonably intact.
- Retina should be in place and there should not be extreme optic nerveOptic nerveThe optic nerve, also called cranial nerve 2, transmits visual information from the retina to the brain. Derived from the embryonic retinal ganglion cell, a diverticulum located in the diencephalon, the optic nerve doesn't regenerate after transection.-Anatomy:The optic nerve is the second of...
cupping. - Opposite eye has reduced vision.
- Intact nasal light projection.
- Consider shuntShuntShunt may refer to:* Shunt - a hole or passage allowing fluid to move from one part of the body to another* Shunt - a device allowing electrical current to pass around a point in a circuit...
if patient is suffering from advanced stage of glaucomaGlaucomaGlaucoma is an eye disorder in which the optic nerve suffers damage, permanently damaging vision in the affected eye and progressing to complete blindness if untreated. It is often, but not always, associated with increased pressure of the fluid in the eye...
.
Procedure
On the day of the procedure, the patient will arrive to the hospital where the surgery is to be performed. After a brief physical examination, he/she will be taken to the operating room. General anesthesia or local anesthesiaLocal anesthesia
Local anesthesia is any technique to induce the absence of sensation in part of the body, generally for the aim of inducing local analgesia, that is, local insensitivity to pain, although other local senses may be affected as well. It allows patients to undergo surgical and dental procedures with...
is given before the surgery begins.
An eyelid speculum
Speculum
The term speculum, Latin for "mirror", and its plural specula, may refer to:* Speculum , a medical tool used for examining body cavities* Speculum , a journal of medieval studies published by the Medieval Academy of America...
is used to keep the eye open throughout the surgery. Some lubrication may be used to prevent the eye from drying. An incision is made at the junction of the cornea and sclera
Sclera
The sclera , also known as the white or white of the eye, is the opaque , fibrous, protective, outer layer of the eye containing collagen and elastic fiber. In the development of the embryo, the sclera is derived from the neural crest...
. An intralamellar pocket is created within the cornea. The artificial cornea is then inserted into the intralamellar pocket. The flap is then repositioned and the incision is closed.
Typically, there is a follow up session few days after surgery, when patients’ complaints are addressed and modifications are made, if needed.
Since Keratoprosthesis is a fairly rare surgical procedure, constant attempts are being made to improve the outcome of the surgery. Also, the material and design used in the artificial cornea may vary and as a result of this, there can be minor variations in surgical procedure as well.
The surgery is done on an outpatient basis with the patient returning home the same day.
Risks
Though the rate of success with Keratoprosthesis is high, in rare cases, certain serious complications could occur.- Glaucoma and extrusionExtrusionExtrusion is a process used to create objects of a fixed cross-sectional profile. A material is pushed or drawn through a die of the desired cross-section...
of the implant are serious complications that could occur. - Sudden vitritis can cause a drastic reduction in vision. However, it is possible to treat this condition through antibiotics or by a minor laser surgeryLaser surgeryLaser surgery is surgery using a laser to cut tissue instead of a scalpel. Examples include the use of a laser scalpel in otherwise conventional surgery, and soft tissue laser surgery, in which the laser beam vaporizes soft tissue with high water content...
. - Inflammation of the eye tissue could occur. This condition is also treatable.
Prognosis
The primary purpose of Keratoprosthesis is to improve vision in patients with complex ocular diseases who are at high risk for donor graft failure. After an impressive success record with Keratoprosthesis in adults, the procedure is used to treat young patients with severe ocular deformities.Economics of the surgery
Keratoprosthesis is continuously evolving with newer generation materials that seek to improve treatment outcomes. However, the cost of surgery is on the expensive side and can typically run up to $35,000 in the US. In order to obtain surgical treatment at a lower cost, many patients choose to get the treatment done form popular medical tourism destinations like IndiaIndia
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
and Singapore
Singapore
Singapore , officially the Republic of Singapore, is a Southeast Asian city-state off the southern tip of the Malay Peninsula, north of the equator. An island country made up of 63 islands, it is separated from Malaysia by the Straits of Johor to its north and from Indonesia's Riau Islands by the...
where the cost of treatment may be as little as one fourth the cost as in the US or UK.
See also
- Osteo-Odonto-KeratoprosthesisOsteo-Odonto-KeratoprosthesisOsteo-odonto-keratoprosthesis is a medical procedure to restore vision in the most severe cases of corneal and ocular surface patients. It includes removal of a tooth from the patient or a donor. After this, a lamina of tissue cut from the tooth is drilled and the hole is fitted with optics...
- Boston keratoprosthesisBoston keratoprosthesisThe Boston Keratoprosthesis is a collar button design keratoprosthesis or artificial cornea. It is composed of a front plate with a stem, which houses the optical portion of the device, a back plate and a titanium locking c-ring. It is available in type I and type II formats...
- AlphaCor