Boston keratoprosthesis | |
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Specialty | ophthalmology |
Boston keratoprosthesis (Boston KPro) is a collar button design keratoprosthesis or artificial cornea. [1] 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. [2] It is available in type I and type II formats. The type I design is used much more frequently than the type II which is reserved for severe end stage dry eye conditions and is similar to the type I except it has a 2 mm anterior nub designed to penetrate through a tarsorrhaphy. The type I format will be discussed here as it is more commonly used.
The type I Kpro is available in single standard pseudophakic power or customized aphakic optic with an 8.5 mm diameter adult size or 7.0 mm diameter pediatric size back plate. The device is currently machined from medical grade polymethylmethacrylate (PMMA) in Wilmington, Massachusetts in the United States. [3] During implantation of the device, the device is assembled with a donor corneal graft positioned between the front and back plate which is then sutured into place in a similar fashion to penetrating keratoplasty (corneal transplantation). [4]
The Boston KPro is a treatment option for corneal disorders not amenable to standard penetrating keratoplasty (corneal transplantation) or corneal transplant. The Boston KPro is a proven primary treatment option for repeat graft failure, [5] herpetic keratitis, [6] aniridia [7] and many pediatric congenital corneal opacities including Peter's anomaly. [8] The device is also used to treat cicatrizing conditions including Stevens–Johnson syndrome [9] and ocular cicatricial pemphigoid, and also ocular burns. [10] [11]
Most common postoperative complications in order of decreasing prevalence include retroprosthetic membrane (RPM), elevated intraocular pressure/glaucoma, infectious endophthalmitis, sterile vitritis, retina detachment (rare) and vitreous hemorrhage (rare). [12] [13] [14] [15]
Four major studies have been completed to date showing outcomes with the type I Boston KPro:
Boston ophthalmologist Claes Dohlman began developing the Boston keratoprosthesis in 1965, [19] and refined it over the next decades. [20] It was approved by the U.S. Food and Drug Administration in 1992. [20] Fewer than 50 of the devices had been implanted before 2002, when popularity began increasing. [21] 1,161 had been placed by 2009, [21] 8,000 by 2012, [22] and 9,000 by 2014. [21]
The design of the device has evolved over its history. In 1996, eight holes were added in the back plate. [21] The holes allow the aqueous humour fluids of the eye to provide nutrients to the donor graft stroma and keratocytes. [23] The device is now available with either eight or 16 holes. [21] In 2004, a titanium locking c-ring was added to prevent intraocular unscrewing of the device. [2] In 2007, a threadless design replaced the previous screw-type one, simplifying assembly and reducing damage to the donor graft when the device is assembled during the surgical procedure. [23] The back plate was changed to titanium in 2012, due to titanium's biocompatibility. [21]
Keratoconus (KC) is a disorder of the eye that results in progressive thinning of the cornea. This may result in blurry vision, double vision, nearsightedness, irregular astigmatism, and light sensitivity leading to poor quality-of-life. Usually both eyes are affected. In more severe cases a scarring or a circle may be seen within the cornea.
LASIK or Lasik, commonly referred to as laser eye surgery or laser vision correction, is a type of refractive surgery for the correction of myopia, hyperopia, and an actual cure for astigmatism, since it is in the cornea. LASIK surgery is performed by an ophthalmologist who uses a laser or microkeratome to reshape the eye's cornea in order to improve visual acuity. For most people, LASIK provides a long-lasting alternative to eyeglasses or contact lenses.
Eye surgery, also known as ophthalmic or ocular surgery, is surgery performed on the eye or its adnexa, by an ophthalmologist. Eye surgery is part of ophthalmology. The eye is a fragile organ, and requires due care before, during, and after a surgical procedure to minimize or prevent further damage. An eye surgeon is responsible for selecting the appropriate surgical procedure for the patient, and for taking the necessary safety precautions. Mentions of eye surgery can be found in several ancient texts dating back as early as 1800 BC, with cataract treatment starting in the fifth century BC. It continues to be a widely practiced class of surgery, with various techniques having been developed for treating eye problems.
Refractive eye surgery is optional eye surgery used to improve the refractive state of the eye and decrease or eliminate dependency on glasses or contact lenses. This can include various methods of surgical remodeling of the cornea (keratomileusis), lens implantation or lens replacement. The most common methods today use excimer lasers to reshape the curvature of the cornea. Refractive eye surgeries are used to treat common vision disorders such as myopia, hyperopia, presbyopia and astigmatism.
The corneal endothelium is a single layer of endothelial cells on the inner surface of the cornea. It faces the chamber formed between the cornea and the iris.
Corneal transplantation, also known as corneal grafting, is a surgical procedure where a damaged or diseased cornea is replaced by donated corneal tissue. When the entire cornea is replaced it is known as penetrating keratoplasty and when only part of the cornea is replaced it is known as lamellar keratoplasty. Keratoplasty simply means surgery to the cornea. The graft is taken from a recently deceased individual with no known diseases or other factors that may affect the chance of survival of the donated tissue or the health of the recipient.
Fuchs dystrophy, also referred to as Fuchs endothelial corneal dystrophy (FECD) and Fuchs endothelial dystrophy (FED), is a slowly progressing corneal dystrophy that usually affects both eyes and is slightly more common in women than in men. Although early signs of Fuchs dystrophy are sometimes seen in people in their 30s and 40s, the disease rarely affects vision until people reach their 50s and 60s.
Tonometry is the procedure eye care professionals perform to determine the intraocular pressure (IOP), the fluid pressure inside the eye. It is an important test in the evaluation of patients at risk from glaucoma. Most tonometers are calibrated to measure pressure in millimeters of mercury (mmHg), with the normal eye pressure range between 10 and 21 mmHg (13–28 hPa).
José Ignacio Barraquer Moner was a Spanish ophthalmologist and inventor born in Barcelona who did most of his life's work in Bogotá, Colombia.
Corneal neovascularization (CNV) is the in-growth of new blood vessels from the pericorneal plexus into avascular corneal tissue as a result of oxygen deprivation. Maintaining avascularity of the corneal stroma is an important aspect of corneal pathophysiology as it is required for corneal transparency and optimal vision. A decrease in corneal transparency causes visual acuity deterioration. Corneal tissue is avascular in nature and the presence of vascularization, which can be deep or superficial, is always pathologically related.
Pellucid marginal degeneration (PMD) is a degenerative corneal condition, often confused with keratoconus. It typically presents with painless vision loss affecting both eyes. Rarely, it may cause acute vision loss with severe pain due to perforation of the cornea. It is typically characterized by a clear, bilateral thinning (ectasia) in the inferior and peripheral region of the cornea, although some cases affect only one eye. The cause of the disease remains unclear.
Keratoprosthesis is a surgical procedure where a diseased cornea is replaced with an artificial cornea. Traditionally, keratoprosthesis is recommended after a person has had a failure of one or more donor corneal transplants. More recently, a less invasive, non-penetrating artificial cornea has been developed which can be used in more routine cases of corneal blindness. 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 with severely damaged cornea due to congenital birth defects, infections, injuries and burns.
Peter S. Hersh is an American ophthalmologist and specialist in LASIK eye surgery, keratoconus, and diseases of the cornea. He co-authored the article in the journal Ophthalmology that presented the results of the study that led to the first approval by the U.S. Food and Drug Administration (FDA) of the excimer laser for the correction of nearsightedness in the United States. Hersh was also medical monitor of the study that led to approval of corneal collagen crosslinking for the treatment of keratoconus.
Sheraz Daya is a British ophthalmologist. Daya founded the Centre for Sight in 1996, and works in stem-cell research and sight recovery surgery.
Reza Dana is the Claes H. Dohlman Professor of Ophthalmology, senior scientist and W. Clement Stone Clinical Research Scholar at Massachusetts Eye and Ear, Harvard Medical School, and director of the Harvard-Vision Clinical Scientist Development Program.
Mooren's ulcer is a rare idiopathic ocular disorder that may lead to blindness due to progressive destruction of the peripheral cornea. Although the etiology of Mooren's ulcer is poorly understood, recent evidence suggests that the pathogenesis of this disease appears to be the result of an autoimmune process directed against molecules expressed in the corneal stroma.
Pre Descemet's endothelial keratoplasty (PDEK) is a kind of endothelial keratoplasty, where the pre descemet's layer (PDL) along with descemet's membrane (DM) and endothelium is transplanted. Conventionally in a corneal transplantation, doctors use a whole cornea or parts of the five layers of the cornea to perform correction surgeries. In May 2013, Dr Harminder Dua discovered a sixth layer between the stroma and the descemet membrane which was named after him as the Dua's layer. In the PDEK technique, doctors take the innermost two layers of the cornea, along with the Dua's layer and graft it in the patient's eye.
Intravitreal injection is the method of administration of drugs into the eye by injection with a fine needle. The medication will be directly applied into the vitreous humor. It is used to treat various eye diseases, such as age-related macular degeneration (AMD), diabetic retinopathy, and infections inside the eye such as endophthalmitis. As compared to topical administration, this method is beneficial for a more localized delivery of medications to the targeted site, as the needle can directly pass through the anatomical eye barrier and dynamic barrier. It could also minimize adverse drug effect to other body tissues via the systemic circulation, which could be a possible risk for intravenous injection of medications. Although there are risks of infections or other complications, with suitable precautions throughout the injection process, chances for these complications could be lowered.
The human cornea is a transparent membrane which allows light to pass through it. The word corneal opacification literally means loss of normal transparency of cornea. The term corneal opacity is used particularly for the loss of transparency of cornea due to scarring. Transparency of the cornea is dependent on the uniform diameter and the regular spacing and arrangement of the collagen fibrils within the stroma. Alterations in the spacing of collagen fibrils in a variety of conditions including corneal edema, scars, and macular corneal dystrophy is clinically manifested as corneal opacity. The term corneal blindness is commonly used to describe blindness due to corneal opacity.
Exposure keratopathy is medical condition affecting the cornea of eyes. It can lead to corneal ulceration and permanent loss of vision due to corneal opacity.