Ads
related to: vertex contact lens calculator toric
Search results
Results from the WOW.Com Content Network
Vertex distance is the distance between the back surface of a corrective lens, i.e. glasses (spectacles) or contact lenses, and the front of the cornea. Increasing or decreasing the vertex distance changes the optical properties of the system, by moving the focal point forward or backward, effectively changing the power of the lens relative to ...
A meridian, in this case, is a plane that is incident with the optical axis. For example, a toric lens, when rotated correctly, could focus an object to the image of a horizontal line at one focal distance while focusing a vertical line to a separate focal distance. The power of a toric lens can be specified by describing how the cylinder (the ...
In the US market, soft contact lenses are approved by the US Food and Drug Administration. [2] The American Optometric Association published a contact lens comparison chart called Advantages and Disadvantages of Various Types of Contact Lenses on the differences between them. [3] These include: soft contact lenses; rigid gas-permeable (RGP ...
A pair of contact lenses, positioned with the concave side facing upward. A corrective lens is a transmissive optical device that is worn on the eye to improve visual perception. The most common use is to treat refractive errors: myopia, hypermetropia, astigmatism, and presbyopia.
Artist's impression of Leonardo's method for neutralizing the refractive power of the cornea. Leonardo da Vinci is frequently credited with introducing the idea of contact lenses in his 1508 Codex of the eye, Manual D, [9] wherein he described a method of directly altering corneal power by either submerging the head in a bowl of water or wearing a water-filled glass hemisphere over the eye.
Toric lens surface as "cap" (top-right) from a torus (here with R = 1.2 r). A toric lens is a lens with different optical power and focal length in two orientations perpendicular to each other. One of the lens surfaces is shaped like a "cap" from a torus (see figure at right), and the other one is usually spherical.
While in principle aspheric surfaces can take a wide variety of forms, aspheric lenses are often designed with surfaces of the form = (+ (+)) + + +, [3]where the optic axis is presumed to lie in the z direction, and () is the sag—the z-component of the displacement of the surface from the vertex, at distance from the axis.
Base curve radius (BCR) or simply base curve (BC) is the measure of an important parameter of a lens in optometry. On a spectacle lens, it is the flatter curvature of the front surface. On a contact lens it is the curvature of the back surface and is sometimes referred to as the back central optic radius (BCOR). Typical values for a contact ...
Ads
related to: vertex contact lens calculator toric