Important Glossary Flashcards
Aberration
The resulting degradation of an image that occurs when a point source of light does not result in a single point image after going through the lens or lens system.
The failure of rays to converge at one focus due to defects or limitations in a lens.
Aberration, lateral chromatic
An aberration that produces images of slightly different sizes at the focal length of the lens, depending upon the color of the light.
Aberration, longitudinal chromatic
Occurs when a point light source that is composed of several wavelengths ( such as white light) forms a series of points images along the optical axis. Each of these images is a different color, and each has a slightly different focal length.
Aberration, monochromatic
An aberration that is present even when light is made up of only one wave length (one color).
Aberration, spherical
An aberration that occurs when parallel light from an object enters a large area of a spherical lens surface, and peripheral rays focus at different points on the optic axis than do paraxial rays.
Angle of deviation
The difference between the angle of incidence and the angle of refraction
Accommodation
Focusing of the eye on a near object through relaxation of the ciliary muscle and thickening of the Crystalline lens.
Amblyopia
The loss of vision without any apparent disease of the eye.
Ametropia
Refractive error in which the Eye, when in a state of rest, does not focus the image of an object up on the retina; includes hyperopia, myopia, and astigmatism.
Aniseikonia
A condition in which the ocular image of an object as seen by one eye differs so much in size or shape from that seen by the other eye that the two images cannot be fused into a single impression.
Anisometropia
A condition in which the refractive error of one eye significantly differs from that of the other; each eye must have the same sign, i.e. both eyes are myopic or hyperopic.
Antimetropia
The refractive condition whereby the signs in each eye are opposite; one is hyperbolic while the other is myopic.
Compound Hyperopic Astigmatism
The refractive error which results in two points of focus falling behind the retina.
Compound Myopic Astigmatism
The refractive error which results in two points of focus falling in front of the retina.
Cornea
The clear transparent portion of the outer coat of the eyeball forming the covering of the aqueous chamber.
43 Diopters
1.37 index of refraction
Made up of five layers: Epithelium, Bowman’s membrane, Stroma, Descemet’s membrane, Endothelium
Epithelium
First corneal layer. Acts as a barrier to protect cornea, resists the free flow of fluids from tears and prevents bacteria from entering the stroma. I’m
Bowman’s Membrane
The second corneal layer. It is a smooth acellular, Non-regenerating layer. Acts as a barrier between Epithelium and Stroma.
Stroma
Third layer and thickest part of the cornea making up 99% of its thickness. It refracts and transmits light to the lens and retina.
Descemet’s membrane
Fourth layer of cornea. A thin but strong sheet of tissue that acts as a protective barrier against infection and injury. Composed of collagen fibers and made by the endothelial cells below it.
Endothelium
The corneal endothelium is a single layer of cells that covers the posterior cornea and is organized in a characteristic honeycomb pattern. Human corneal endothelial cells are primarily responsible for regulating stromal hydration, which is inherently related to the transparency of the tissue.
Crystalline Lens
A transparent colorless body suspended in the front part of the eyeball, between the aqueous and the vitreous, the function of which is to bring the rays of light to a focus on the retina.
- 37 Index of refraction
- 00 Diopters
Diplopia
The seeing of one object has two. “Double vision”
Emmetropia
The refractive condition of the normal eye when the eye is at rest, the image of distant objects is brought to a focus on the retina.
Fovea
A small depression in the retina at the back of the eye; the part of the macular adapted for most acute vision. Provides clearest vision of all, and cones are mainly found here as it slowly spreads outward.
Fusion
The power of coordination by which the images received by the two eyes become a single image.
Glaucoma
And ocular disease having as its primary characteristic a sustained increase in intraocular pressure at that I cannot withstand without damage to its structure or impairment of its function.
Hyperopia
The refractive error in which, because the eyeball is shorts or the refractive power of the lens is weak, the point of focus for rays of light from distant objects falls behind the retina; accommodation to increase the refractive power of the lens is necessary for distance vision as well as near vision.
Farsighted
Iris
The colored circular membrane suspended behind the cornea and immediately in front of the lens. The iris regulates the amount of light entering the eye by changing the size of the pupil through dilator and sphincter muscles.
The dilator opens the iris allowing more light in, and the sphincter closes the iris.
The iris has the ability to change the people size from 2 mm to 8 mm.
Irregular Astigmatism
A refractive condition caused by a cornea which is damaged and irregular so that rays of light come to many focal points on the retina; is not correctable by cylinders.
Iseikonic Lenses
Spectacle lenses specially designed to manipulate image size when does similar sizes make it difficult or impossible for fusion to occur; such as in aniseikonia.
Macula
The small area of the retina that surrounds the fovea and that with the fovea, comprises the area of the retina that gives distinct vision.
Mixed Astigmatism
The refractive condition in which light comes to two points of focus where one point is in front of the retina, and the other is behind the retina.
Myopia
A refractive error and wish the eyeball is too long in relation to its focusing power; that’s the point of focus for rays of light from distant objects is in front of the retina.
Nearsighted
Optic nerve
The special nerve of the sense of sight that carries impulses from the retina to the brain.
Phoria
A root word denoting a latent deviation in which the eyes have a constant tendency to turn from the normal position for binocular vision; used with a prefix to indicate the direction of such deviation (for example hyperphoria, esophoria, exophoria)
Presbyopia
A gradual lessening of the power of accommodation due to a physiologic change that becomes noticeable about the age of 40 years.
Corrected with Progressive, bifocal, trifocals
Ptosis ( ptosis crutch)
Abnormal low lying or drooping eyelid
Can be fixed with small spring wire attached nasally to a spectacle frame to lift a drooping lid
Pupil
The central opening of the iris through which light is permitted to enter the eye.
Regular astigmatism
Refractive condition in which rays of light come to tube focal points and it’s correctable by cylinders.
Retina
Innermost coat of the eye, formed of sensitive nerve elements and connected with the optic nerve.
Rods and Cones
Two different kinds of cells that form a layer of the retina and act as like receiving media. Cones are concerned with visual acuity and color discrimination as well as daytime vision. (6,000,000) rods are employed for motion and vision at low degrees of illumination such as night vision, helps with peripheral vision. (120,000,000)
Sclera
The white part of the eye. A tough covering which with the cornea formed the external protective coat of the eye.
Actions
A blind area of reduced vision in the visual field.
Simple Hyperopic Astigmatism
The refractive condition where one point of focus falls on the retina and the other point of focus falls behind retina.
Strabismus
Failure of the two eyes to simultaneously direct their gaze at the same object because of muscle in balance.
Suspensory Ligaments
The suspensory apparatus of the crystalline lens. Numerous fine tissue strands that stretch from the ciliary processes to the lens equator and support the lens in place.
Tropia
A root word denoting an obvious deviation from normal of the axis of the eyes; used with the prefix to denote the type of strabismus. (Heterotropia, esotropia, exotropia)
Vitreous Humor
Transparent, colorless mass of soft, gelatinous material filling the eyeball behind the lens. Helps maintain the shape of the eye, vision clarity and shock absorbency.
Palpebrae
The upper and lower eyelids, termed palpebrae, along with the eyebrows, and eyelashes, help to protect the eyeball from intrusion of foreign matter, excessive light entrance, and injuries due to various causes.
Canthi
Comprised of the medial and lateral canthus. The points where the upper and lower eyelids need near the nose (medium) or towards the ear (lateral)
Aphakia
The absence of the crystalline lens of the eye.
Aqueous Humor
The clear watery fluid that fills the anterior and posterior chamber is within the front part of the eye. It provides nutrition to the eye as well as helping to maintain the pressurized state of the eye.
Astigmatism
A refractive error that prevents the light rays from coming to a single focus on the retina because of different degrees of refraction in the various meridians of the eye.
Cataract
A condition in which the crystalline lens of the eye, or its capsule, or both, become opaque, with consequent loss of visual acuity.
Choroid
The vascular intermediate coat that furnishes nourishment to other parts of the eyeball. Provides oxygen and nourishment to the outer layers of the retina.
Ciliary Body
The portion of the vascular coat between the iris and the choroid consisting of ciliary processes and the ciliary muscle.
The ciliary muscle controls the shape of the lens.
The ciliary processes secrete aqueous humor into the posterior chamber, flows through the pupil into the anterior chamber.
