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Cryolathe
A cryolathe is a device used for freezing and grinding human corneal tissue into different refractive powers. See also *Epikeratophakia *Keratomileusis *Refractive surgery References External links * Medical equipment {{medical-equipment-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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. While the cornea contributes most of the eye's focusing power, its focus is fixed. Accommodation (the refocusing of light to better view near objects) is accomplished by changing the geometry of the lens. Medical terms related to the cornea often start with the prefix "'' kerat-''" from the Greek word κέρας, ''horn''. Structure The cornea has unmyelinated nerve endings sensitive to touch, temperature and chemicals; a touch of the cornea causes an involuntary reflex to close the eyelid. Because transparency is of prime importance, the healthy cornea does not have or need blood vessels with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Refractive Power
In optics, optical power (also referred to as dioptric power, refractive power, focusing power, or convergence power) is the degree to which a lens, mirror, or other optical system converges or diverges light. It is equal to the reciprocal of the focal length of the device: . High optical power corresponds to short focal length. The SI unit for optical power is the inverse metre (m−1), which is commonly called the dioptre. Converging lenses have positive optical power, while diverging lenses have negative power. When a lens is immersed in a refractive medium, its optical power and focal length change. For two or more thin lenses close together, the optical power of the combined lenses is approximately equal to the sum of the optical powers of each lens: . Similarly, the optical power of a single lens is roughly equal to the sum of the powers of each surface. These approximations are commonly used in optometry. An eye that has too much or too little refractive power to focu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Epikeratophakia
Epikeratophakia (also known as epikeratoplasty and onlay lamellar keratoplasty) is a refractive surgical procedure in which a lamella of a donor cornea is transplanted onto the anterior surface of the patient's cornea. A lamellar disc from a donor cornea is placed over the de-epithelialized host cornea and sutured into a prepared groove on the host cornea. Indications include treatment of keratoconus, refractive errors like myopia and high hypermetropia including aphakia, which cannot be corrected with conservative methods. __TOC__ Complications Common complications of epikeratophakia include delayed post operative visual recovery, reduced best corrected visual acuity, prolonged epithelial defects and irregular astigmatism Astigmatism is a type of refractive error due to rotational asymmetry in the eye's refractive power. This results in distorted or blurred vision at any distance. Other symptoms can include eyestrain, headaches, and trouble driving at nig .... Hist ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Keratomileusis
Keratomileusis, from Greek κέρας (kéras: horn) and σμίλευσις (smíleusis: carving),The word is derived from Greek κέρας - keras (root: kerat-) "horn, cornea" and σμίλευσις - smileusis "carving or corneal reshaping, is the Surgery, surgical improvement of the refractive state of the cornea by surgically reshaping it. It is the most common form of refractive surgery. The first usable technique was developed by José Ignacio Barraquer, commonly called "the father of modern refractive surgery." The most common modern procedure, LASIK, is performed by lifting the front surface of the eye by forming a thin hinged flap under which the shape of the cornea is changed by using an excimer laser or other surgical device. A microkeratome is usually used to cut the flap, but a femtosecond laser can also be used to make the flap. Before the advent of the excimer laser, keratomileusis was performed using a cryolathe, which froze thin flaps of corneal tissue and lat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Refractive Surgery
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. History The first theoretical work on the potential of refractive surgery was published in 1885 by Hjalmar August Schiøtz, an ophthalmologist from Norway. In 1930, the Japanese ophthalmologist Tsutomu Sato made the first attempts at performing this kind of surgery, hoping to correct the vision of military pilots. His approach was to make radial cuts in the cornea, correcting effects by up to 6 diopters. The procedure unfortunately produced a high rate of corneal degeneration, howeve ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
