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.
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.
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.
Recurrent corneal erosion is a disorder of the eyes characterized by the failure of the cornea's outermost layer of epithelial cells to attach to the underlying basement membrane. The condition is excruciatingly painful because the loss of these cells results in the exposure of sensitive corneal nerves. This condition can often leave patients with temporary blindness due to extreme light sensitivity (photophobia).
Corneal abrasion is a scratch to the surface of the cornea of the eye. Symptoms include pain, redness, light sensitivity, and a feeling like a foreign body is in the eye. Most people recover completely within three days.
Descemet's membrane is the basement membrane that lies between the corneal proper substance, also called stroma, and the endothelial layer of the cornea. It is composed of different kinds of collagen than the stroma. The endothelial layer is located at the posterior of the cornea. Descemet's membrane, as the basement membrane for the endothelial layer, is secreted by the single layer of squamous epithelial cells that compose the endothelial layer of the cornea.
A corneal ulcer, or ulcerative keratitis, is an inflammatory condition of the cornea involving loss of its outer layer. It is very common in dogs and is sometimes seen in cats. In veterinary medicine, the term corneal ulcer is a generic name for any condition involving the loss of the outer layer of the cornea, and as such is used to describe conditions with both inflammatory and traumatic causes.
Corneal dystrophy is a group of rare hereditary disorders characterised by bilateral abnormal deposition of substances in the transparent front part of the eye called the cornea.
Corneal ulcer is an inflammatory or, more seriously, infective condition of the cornea involving disruption of its epithelial layer with involvement of the corneal stroma. It is a common condition in humans particularly in the tropics and the agrarian societies. In developing countries, children afflicted by Vitamin A deficiency are at high risk for corneal ulcer and may become blind in both eyes, which may persist lifelong. In ophthalmology, a corneal ulcer usually refers to having an infectious cause while the term corneal abrasion refers more to physical abrasions.
The familial amyloid neuropathies are a rare group of autosomal dominant diseases wherein the autonomic nervous system and/or other nerves are compromised by protein aggregation and/or amyloid fibril formation.
Ardalan–Shoja–Kiuru syndrome is a clinical syndrome featuring hereditary gelsolin amyloidosis and retinitis pigmentosa. This syndrome was first recognized by two Iranian physicians, Mohammad Ardalan and Mohammadali Shoja and Finnish neurologist Sari Kiuru-Enari in an Iranian family. Hereditary gelsolin amyloidosis has originally been reported by Finnish ophthalmologist Jouko Meretoja and is known as Meretoja syndrome or Familial Amyloidosis, Finnish type. In addition to the classic manifestations of Finnish type Familial Amyloidosis, cutis laxa, progressive peripheral neuropathy and corneal lattice dystrophy, some of the affected members of the Iranian family have retinitis pigmentosa. This feature had not been previously reported with this type of amyloidosis. Ardalan–Shoja–Kiuru syndrome or hereditary gelsolin amyloidosis plus retinitis pigmentosa has not been found outside this single Iranian family.
Meesmann corneal dystrophy (MECD) is a rare hereditary autosomal dominant disease that is characterized as a type of corneal dystrophy and a keratin disease. MECD is characterized by the formation of microcysts in the outermost layer of the cornea, known as the anterior corneal epithelium. The anterior corneal epithelium also becomes fragile. This usually affects both eyes rather than a single eye and worsens over time. There are two phenotypes, Meesmann corneal dystrophy 1 (MECD1) and Meesmann corneal dystrophy 2 (MECD2), which affect the genes KRT3 and KRT12, respectively. A heterozygous mutation in either of these genes will lead to a single phenotype. Many with Meesmann corneal dystrophy are asymptomatic or experience mild symptoms.
Macular corneal dystrophy, also known as Fehr corneal dystrophy named for German ophthalmologist Oskar Fehr (1871-1959), is a rare pathological condition affecting the stroma of cornea. The first signs are usually noticed in the first decade of life, and progress afterwards, with opacities developing in the cornea and attacks of pain. The condition was first described by Arthur Groenouw in 1890.
Reis-Bücklers corneal dystrophy is a rare, corneal dystrophy of unknown cause, in which the Bowman's layer of the cornea undergoes disintegration. The disorder is inherited in an autosomal dominant fashion, and is associated with mutations in the gene TGFB1.
Gelatinous drop-like corneal dystrophy, also known as amyloid corneal dystrophy, is a rare form of corneal dystrophy. The disease was described by Nakaizumi as early as 1914.
Epithelial basement membrane dystrophy (EBMD) is a disorder of the eye that can cause pain and dryness.
Familial Amyloidosis, Finnish Type (FAF), also called hereditary gelsolin amyloidosis and AGel amyloidosis (AGel), is an amyloid condition with a number of associated cutaneous and neurological presentations deriving from the aberrant proteolysis of a mutated form of plasma gelsolin. First described in 1969 by the Finnish ophthalmologist Jouko Meretoja, FAF is uncommon with 400-600 cases described in Finland and 15 elsewhere.
Herpetic simplex keratitis is a form of keratitis caused by recurrent herpes simplex virus (HSV) infection in the cornea.
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.
