Chapter 5-Optics And Refractive States Of The Eye Flashcards
Physical Optics
The study of optics that describes the nature of light in terms of its wave properties.
Optics
The branch of physical science that deals with the properties of light and vision.
Geometric Optics
The area of optics that deals with the transmission of light as rays and is concerned with the effect of lenses on light and the production of images.
Electromagnetic Radiation
Radiation produced through the combination of electrical and magnetic forces; includes rays from the shortest to longest wavelengths.
Opaque
Refers to a substance that completely blocks light.
Translucent
Refers to a substance that transmits light but significantly interferes with its passage.
Transparent
Refers to a substance that permits the passage of light without significant disruption.
Refracted
Refers to the change in directions of a light ray when it passes from one medium to another.
Optical density
A lens property that increases the effectiveness to bend light.
Refractive Index
The ratio of the speed of light in a vacuum to its speed through a specific substance.
Prism
A triangular piece of glass or plastic with flat sides, an apex, and a base.
Plane
Flat
Apex
The top, as of a prism.
Base
The bottom, as of a prism.
Converge
To come together.
Diverge
To spread apart.
Convex Lens
A piece of glass or plastic in which one or both surfaces are curved outward. Also called a positive lens or plus lens.
Concave Lens
A piece of glass or plastic which or both surfaces are curved inward. Also called negative lens or minus lens.
Parallel
Refers to rays that travel side by side in the same direction, neither diverging nor converging.
Principal Axis
The pathway of a light ray that strikes the center of a lens of any shape and passes undeviated through the lens material.
Axial Ray/Principal Ray
A light ray that strikes the center of a lens of any shape and passes undeviated through the lens material.
Paraxial Ray
Light rays that enter a lens system away from the center.
Focal Point
The point somewhere along the principal axis at which the paraxial rays from a distant source are refracted by a lens and converge in the case of a convex lens and diverge in the case of a concave lens.
Virtual image
The image formed by a concave lens when the paraxial rays from a distant source are refracted and diverge.
Vergence Power/Power
The measure of a lens’s ability to converge or diverge.
Focal Length
The distance between the focal point and the lens.
Diopter
The unit of measure of the power of a lens.
Accommodation
The change in the curvature of the crystalline lens that helps to focus images of objects close to the eye.
Refractive State
The relative ability of the refractive components of the eye to bring objects into focus on the retina.
Emmetropia
The refractive state of an eye that is able to focus correctly without the need for optical lenses.
Ametropia
The refractive state of an eye that is unable to focus correctly due to a refractive error.
Refractive Errors
A nonpathologic deficiency in the eye’s optical system.
Presbyopia
The progressive loss of the accommodative ability of the lens, due to natural processes of aging.
Myopia
Nearsightedness. If the eye is too long for its optical system the condition is called axial myopia. If the refractive power is excessive for the length of the eye, the condition is called refractive myopia.
Spherical Cornea
A cornea (of the normal eye and most myopic and hyperopia eyes) whose curvature is uniform.
Toric Cornea
A cornea whose surface curvature is not uniform.
Astigmatism
The refractive error of an eye whose corneal surface curvature is greater in on meridian than another, both distant and near objects appear blurred and distorted.
Principal Meridians
The meridians of maximum and minimum corneal curvature.
Regular Astigmatism
The most common form of astigmatism, in which the cornea resembles a football standing on one end or on it’s side.
Irregular Astigmatism
The less common form of astigmatism, in which the corneal surface loses its uniformity secondary to scarring or other pathology.
Hyperopia
Farsightedness. If the eye is too short for its optical system the condition is called axial hyperopia. If the refractive power is insufficient for the length of the eye the condition is called refractive hyperopia.
Spherical Lens/Sphere
A concave or convex lens whose curvature is uniform, allowing it to focus light rays to a single point.
Bifocals
A lens with two visual purposes; commonly the correction of both distance and near vision.
Trifocals
One that has three powers: one for correcting distance vision, one for correcting intermediate range of sight, and one for correcting near vision.
Multifocal Lens
Bifocal lens/Trifocal lens
Add
The portion of the multifocal lens (usually the lower part) that provides correction for near vision.
