Emmetropia: The condition of where images are correctly brought to a focus on the retina.Refraction, Ocular: Refraction of LIGHT effected by the media of the EYE.Myopia: A refractive error in which rays of light entering the EYE parallel to the optic axis are brought to a focus in front of the RETINA when accommodation (ACCOMMODATION, OCULAR) is relaxed. This results from an overly curved CORNEA or from the eyeball being too long from front to back. It is also called nearsightedness.Cyclopentolate: A parasympatholytic anticholinergic used solely to obtain mydriasis or cycloplegia.Hyperopia: A refractive error in which rays of light entering the eye parallel to the optic axis are brought to a focus behind the retina, as a result of the eyeball being too short from front to back. It is also called farsightedness because the near point is more distant than it is in emmetropia with an equal amplitude of accommodation. (Dorland, 27th ed)Refractive Errors: Deviations from the average or standard indices of refraction of the eye through its dioptric or refractive apparatus.Mydriatics: Agents that dilate the pupil. They may be either sympathomimetics or parasympatholytics.Myopia, Degenerative: Excessive axial myopia associated with complications (especially posterior staphyloma and CHOROIDAL NEOVASCULARIZATION) that can lead to BLINDNESS.Accommodation, Ocular: The dioptric adjustment of the EYE (to attain maximal sharpness of retinal imagery for an object of regard) referring to the ability, to the mechanism, or to the process. Ocular accommodation is the effecting of refractive changes by changes in the shape of the CRYSTALLINE LENS. Loosely, it refers to ocular adjustments for VISION, OCULAR at various distances. (Cline et al., Dictionary of Visual Science, 4th ed)Retinoscopy: An objective determination of the refractive state of the eye (NEARSIGHTEDNESS; FARSIGHTEDNESS; ASTIGMATISM). By using a RETINOSCOPE, the amount of correction and the power of lens needed can be determined.Axial Length, Eye: The distance between the anterior and posterior poles of the eye, measured either by ULTRASONOGRAPHY or by partial coherence interferometry.Astigmatism: Unequal curvature of the refractive surfaces of the eye. Thus a point source of light cannot be brought to a point focus on the retina but is spread over a more or less diffuse area. This results from the radius of curvature in one plane being longer or shorter than the radius at right angles to it. (Dorland, 27th ed)Biometry: The use of statistical and mathematical methods to analyze biological observations and phenomena.Refractive Surgical Procedures: Surgical procedures employed to correct REFRACTIVE ERRORS such as MYOPIA; HYPEROPIA; or ASTIGMATISM. These may involve altering the curvature of the CORNEA; removal or replacement of the CRYSTALLINE LENS; or modification of the SCLERA to change the axial length of the eye.Eye: The organ of sight constituting a pair of globular organs made up of a three-layered roughly spherical structure specialized for receiving and responding to light.Photorefractive Keratectomy: A type of refractive surgery of the CORNEA to correct MYOPIA and ASTIGMATISM. An EXCIMER LASER is used directly on the surface of the EYE to remove some of the CORNEAL EPITHELIUM thus reshaping the anterior curvature of the cornea.Lasers, Excimer: Gas lasers with excited dimers (i.e., excimers) as the active medium. The most commonly used are rare gas monohalides (e.g., argon fluoride, xenon chloride). Their principal emission wavelengths are in the ultraviolet range and depend on the monohalide used (e.g., 193 nm for ArF, 308 nm for Xe Cl). These lasers are operated in pulsed and Q-switched modes and used in photoablative decomposition involving actual removal of tissue. (UMDNS, 2005)Eyeglasses: A pair of ophthalmic lenses in a frame or mounting which is supported by the nose and ears. The purpose is to aid or improve vision. It does not include goggles or nonprescription sun glasses for which EYE PROTECTIVE DEVICES is available.Lenses, Intraocular: Artificial implanted lenses.Visual Acuity: Clarity or sharpness of OCULAR VISION or the ability of the eye to see fine details. Visual acuity depends on the functions of RETINA, neuronal transmission, and the interpretative ability of the brain. Normal visual acuity is expressed as 20/20 indicating that one can see at 20 feet what should normally be seen at that distance. Visual acuity can also be influenced by brightness, color, and contrast.Cornea: The transparent anterior portion of the fibrous coat of the eye consisting of five layers: stratified squamous CORNEAL EPITHELIUM; BOWMAN MEMBRANE; CORNEAL STROMA; DESCEMET MEMBRANE; and mesenchymal CORNEAL ENDOTHELIUM. It serves as the first refracting medium of the eye. It is structurally continuous with the SCLERA, avascular, receiving its nourishment by permeation through spaces between the lamellae, and is innervated by the ophthalmic division of the TRIGEMINAL NERVE via the ciliary nerves and those of the surrounding conjunctiva which together form plexuses. (Cline et al., Dictionary of Visual Science, 4th ed)Exfoliation Syndrome: The deposition of flaky, translucent fibrillar material most conspicuous on the anterior lens capsule and pupillary margin but also in both surfaces of the iris, the zonules, trabecular meshwork, ciliary body, corneal endothelium, and orbital blood vessels. It sometimes forms a membrane on the anterior iris surface. Exfoliation refers to the shedding of pigment by the iris. (Newell, Ophthalmology, 7th ed, p380)Lens Implantation, Intraocular: Insertion of an artificial lens to replace the natural CRYSTALLINE LENS after CATARACT EXTRACTION or to supplement the natural lens which is left in place.Pigmentation DisordersIris Diseases: Diseases, dysfunctions, or disorders of or located in the iris.Iris: The most anterior portion of the uveal layer, separating the anterior chamber from the posterior. It consists of two layers - the stroma and the pigmented epithelium. Color of the iris depends on the amount of melanin in the stroma on reflection from the pigmented epithelium.Cataract Extraction: The removal of a cataractous CRYSTALLINE LENS from the eye.Contrast Sensitivity: The ability to detect sharp boundaries (stimuli) and to detect slight changes in luminance at regions without distinct contours. Psychophysical measurements of this visual function are used to evaluate visual acuity and to detect eye disease.Corneal Wavefront Aberration: Asymmetries in the topography and refractive index of the corneal surface that affect visual acuity.Vision Tests: A series of tests used to assess various functions of the eyes.Encyclopedias as Topic: Works containing information articles on subjects in every field of knowledge, usually arranged in alphabetical order, or a similar work limited to a special field or subject. (From The ALA Glossary of Library and Information Science, 1983)EncyclopediasDictionaries, MedicalDictionaries as Topic: Lists of words, usually in alphabetical order, giving information about form, pronunciation, etymology, grammar, and meaning.Molecular Sequence Annotation: The addition of descriptive information about the function or structure of a molecular sequence to its MOLECULAR SEQUENCE DATA record.Databases, Genetic: Databases devoted to knowledge about specific genes and gene products.Catheter Ablation: Removal of tissue with electrical current delivered via electrodes positioned at the distal end of a catheter. Energy sources are commonly direct current (DC-shock) or alternating current at radiofrequencies (usually 750 kHz). The technique is used most often to ablate the AV junction and/or accessory pathways in order to interrupt AV conduction and produce AV block in the treatment of various tachyarrhythmias.Patents as Topic: Exclusive legal rights or privileges applied to inventions, plants, etc.Laser Therapy: The use of photothermal effects of LASERS to coagulate, incise, vaporize, resect, dissect, or resurface tissue.Lasers: An optical source that emits photons in a coherent beam. Light Amplification by Stimulated Emission of Radiation (LASER) is brought about using devices that transform light of varying frequencies into a single intense, nearly nondivergent beam of monochromatic radiation. Lasers operate in the infrared, visible, ultraviolet, or X-ray regions of the spectrum.Varicose Veins: Enlarged and tortuous VEINS.Foramen Ovale, Patent: A condition in which the FORAMEN OVALE in the ATRIAL SEPTUM fails to close shortly after birth. This results in abnormal communications between the two upper chambers of the heart. An isolated patent ovale foramen without other structural heart defects is usually of no hemodynamic significance.Lasers, Semiconductor: Lasers with a semiconductor diode as the active medium. Diode lasers transform electric energy to light using the same principle as a light-emitting diode (LED), but with internal reflection capability, thus forming a resonator where a stimulated light can reflect back and forth, allowing only a certain wavelength to be emitted. The emission of a given device is determined by the active compound used (e.g., gallium arsenide crystals doped with aluminum or indium). Typical wavelengths are 810, 1,060 and 1,300 nm. (From UMDNS, 2005)Herbicides: Pesticides used to destroy unwanted vegetation, especially various types of weeds, grasses (POACEAE), and woody plants. Some plants develop HERBICIDE RESISTANCE.Glucuronates: Derivatives of GLUCURONIC ACID. Included under this heading are a broad variety of acid forms, salts, esters, and amides that include the 6-carboxy glucose structure.Chromatography, Paper: An analytical technique for resolution of a chemical mixture into its component compounds. Compounds are separated on an adsorbent paper (stationary phase) by their varied degree of solubility/mobility in the eluting solvent (mobile phase).Cyanides: Inorganic salts of HYDROGEN CYANIDE containing the -CN radical. The concept also includes isocyanides. It is distinguished from NITRILES, which denotes organic compounds containing the -CN radical.Algorithms: A procedure consisting of a sequence of algebraic formulas and/or logical steps to calculate or determine a given task.Acholeplasma: A genus of gram-negative organisms including saprophytic and parasitic or pathogenic species.Software: Sequential operating programs and data which instruct the functioning of a digital computer.Medical Laboratory Science: The specialty related to the performance of techniques in clinical pathology such as those in hematology, microbiology, and other general clinical laboratory applications.Technology, High-Cost: Advanced technology that is costly, requires highly skilled personnel, and is unique in its particular application. Includes innovative, specialized medical/surgical procedures as well as advanced diagnostic and therapeutic equipment.Ophthalmologic Surgical Procedures: Surgery performed on the eye or any of its parts.Biomedical Technology: The application of technology to the solution of medical problems.Anesthesia, Local: A blocking of nerve conduction to a specific area by an injection of an anesthetic agent.Terminology as Topic: The terms, expressions, designations, or symbols used in a particular science, discipline, or specialized subject area.