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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.
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Along with the anterior chamber and lens, the cornea refracts light, accounting for approximately two-thirds of the eye's total optical power. In humans, the refractive power of the cornea is approximately 43 dioptres. The cornea can be reshaped by surgical procedures such as LASIK.
A pterygium of the eye is a pinkish, roughly triangular tissue growth of the conjunctiva onto the cornea of the eye. It typically starts on the cornea near the nose. It may slowly grow but rarely grows so large that it covers the pupil and impairs vision. Often both eyes are involved.
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.
Eduard Konrad Zirm was an ophthalmologist who performed the first successful human full-thickness corneal transplant on 7 December 1905.
Eye banks recover, prepare and deliver donated eyes for cornea transplants and research. The first successful cornea transplant was performed in 1905 and the first eye bank was founded in 1944. Currently, in the United States, eye banks provide tissue for over 80,000 cornea transplants each year to treat conditions such as keratoconus and corneal scarring. In some cases, the white of the eye (sclera) is used to surgically repair recipient eyes. Unlike other organs and tissues, there is an adequate supply of corneas for transplants in the United States, and excess tissue is exported internationally, where there are shortages in many countries, due to greater demand and a less-developed eye banking infrastructure.
Acanthamoeba keratitis (AK) is a rare disease in which amoebae of the genus Acanthamoeba invade the clear portion of the front (cornea) of the eye. It affects roughly 100 people in the United States each year. Acanthamoeba are protozoa found nearly ubiquitously in soil and water and can cause infections of the skin, eyes, and central nervous system.
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.
Transplantable organs and tissues may both refer to organs and tissues that are relatively often or routinely transplanted, as well as relatively seldom transplanted organs and tissues and ones on the experimental stage.
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 suffering from severely damaged cornea due to congenital birth defects, infections, injuries and burns.
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. 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.
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.
Jeewan Singh Titiyal is an Indian ophthalmologist, credited with the first live cornea transplant surgery by an Indian doctor. He was honoured by the Government of India, in 2014, by bestowing on him the Padma Shri, the fourth highest civilian award, for his services to the field of medicine.
Limbal stem cells, also known as corneal epithelial stem cells, are stem cells located in the basal epithelial layer of the corneal limbus. They form the border between the cornea and the sclera. Characteristics of limbal stem cells include a slow turnover rate, high proliferative potential, clonogenicity, expression of stem cell markers, as well as the ability to regenerate the entire corneal epithelium. Limbal stem cell proliferation has the role of maintaining the cornea; for example, by replacing cells that are lost via tears. Additionally, these cells also prevent the conjunctival epithelial cells from migrating onto the surface of the cornea.
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.
Virender Singh Sangwan is an Indian ophthalmologist and the Dr. Paul Dubord Chair professor and director of the L. V. Prasad Eye Institute, Hyderabad. Known for his research on limbal stem cells, Sangwan is the founder secretary and an adviser of the Uveitis Society of India. The Council of Scientific and Industrial Research, the apex agency of the Government of India for scientific research, awarded him the Shanti Swarup Bhatnagar Prize for Science and Technology, one of the highest Indian science awards for his contributions to Medical Sciences in 2006.
A corneal button is a replacement cornea to be transplanted in the place of a damaged or diseased cornea normally approximately 8.5–9.0mm in diameter. It is used in a corneal transplantation procedure whereby the whole, or part, of a cornea is replaced. The donor tissue can now be held for days to even weeks of the donor's death and is normally a small, rounded shape. The main use of the corneal button is during procedures where the entirety of the cornea needs to be replaced, also known as penetrating keratoplasty.
References
- ↑ Corneal Graft Rejection on eMedicine
- ↑ "Atlas of Ophthalmology". Atlasophthalmology.com. Archived from the original on 2011-07-07. Retrieved 2011-01-02.
