Biomaterial Database

Spherocylindrical refractive errors and visual acuity. 1995

T W Raasch

Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.

BACKGROUND Understanding the relation between refractive error and visual acuity is complicated if astigmatic blur is present. No models are in widespread use that allow the combination of spherical and astigmatic errors for the purpose of predicting visual performance. METHODS Models for combining spherical and astigmatic errors are discussed, and predictions of these models using data from the literature are presented. RESULTS Three models for combining astigmatic with spherical errors are shown to predict visual acuity performance in uncorrected myopic refractive errors. A dioptric vector addition model is shown to have advantages over other candidate models. CONCLUSIONS It is possible to combine spherocylindrical refractive errors into a single value when the objective is to correlate these values with visual acuity performance.

UI	MeSH Term	Description	Entries
D008433	Mathematics	The deductive study of shape, quantity, and dependence. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)	Mathematic
D008954	Models, Biological	Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment.	Biological Model,Biological Models,Model, Biological,Models, Biologic,Biologic Model,Biologic Models,Model, Biologic
D012030	Refractive Errors	Deviations from the average or standard indices of refraction of the eye through its dioptric or refractive apparatus.	Ametropia,Refractive Disorders,Ametropias,Disorder, Refractive,Disorders, Refractive,Error, Refractive,Errors, Refractive,Refractive Disorder,Refractive Error
D005139	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.	Glasses,Spectacles,Sun Glasses, Prescription,Glasses, Prescription Sun,Prescription Sun Glasses
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D014792	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.	Acuities, Visual,Acuity, Visual,Visual Acuities
D055095	Optics and Photonics	A specialized field of physics and engineering involved in studying the behavior and properties of light and the technology of analyzing, generating, transmitting, and manipulating ELECTROMAGNETIC RADIATION in the visible, infrared, and ultraviolet range.	Photonics,Photonics and Optics