3 Intro To Vision Flashcards
Accommodation (focus)
In vision, bringing objects located at different distances into focus by changing the shape of the lens.
Absorption spectrum
Plot of the amount of light absorbed by a visual pigment versus the wavelength of light.
Amacrine cells
Neuron that transmits signals laterally in the retina. Amacrime cells synapse with bipolar cells and ganglion cells.
Axial myopia
Myopia (nearsightedness) in which the eyeball is too long.
Belongingness
Hypothesis that an area’s appearance is influenced by the part of the surroundings that the area appears to belong to. This principle has been used to explain the perception of whiteness in the Benary cross and White’s Illusion.
Bipolar cells
Retinal neurons that receives input from the visual receptors and send signals to the retinal ganglion cells.
Blind spot
Small area where the optic nerve leaves the back of the eye. There are no visual receptors in this area, so small images falling directly on the blind spot cannot be seen.
Cone
Cone-shaped receptors in the retina that are primarily responsible for vision in high levels of illumination and for color vision and detailed vision.
Cornea
Transparent focusing element of the eye that is the first structure through which light passes as it enters the eye. The cornea is that I possibly have some major focusing element.
Dark adaption
Visual adaption that occurs in the dark, during which the sensitivity to light increases. This increase in sensitivity is associated with regeneration of the rod and cone visual pigments.
Dark adoption curve
Function that traces the time course of the increasing visual sensitivity that occurs during dark adaptation.
Dark-adapted sensitivity
Sensitivity of the eye after it has completely adapted to the dark.
Detached retina
Condition in which the retina detached from the back of the eye.
Electromagnetic spectrum
Continuum of electromagnetic energy that extends from very-short-wavelength gamma rays to long-wavelength radio waves. Visible light is a new band within the spectrum.
Enzyme cascade
Sequence of reactions triggered by an activated visual pigment molecule that results in transduction.
Eye
Eyeball and its contents, which include focusing elements, the retina, and supporting structures.
Far point
Distance at which the spot of light becomes focused on the retina.
Farsightedness
Hyperopia
Fovea
Small area in the human retina contains only cone receptors. The fovea is located on the line of sight, so that when a person looks at an object, the center of its image falls on the fovea.
Ganglion cells
Neuron in the retina receives inputs from bipolar and amacrine cells. The axons of the ganglion cells travel out of the eye in the optic nerve.
Hermann grade
Geometrical display that results in the illusion of dark areas at the intersection of two white “corridors.” This perception can be explained by lateral inhibition.
Horizontal cells
Neurons that transmits signals laterally across the retina. Horizontal cells synapse with receptors and bipolar cells.
Hyperopia
Condition causing poor vision he which people can see objects that are far away but do not see near objects clearly. Farsightedness.
Isomerization
Changing shape of the retinal part of the visual pigment molecule that occurs when the molecule absorbs a quantum of light. Isomerization triggers the enzyme cascade that result in transduction from light energy to electrical energy into retinal receptors.
Laser-assisted in situ keratomileusis
Process in which the cornea is sculpted with the laser in order to achieve clear vision by adjusting the focusing power of the cornea so it focuses light onto the retina.
Lateral inhibition
In addition that is transmitted laterally across a neural circuit. In the retina, lateral inhibition is transmitted by the horizontal and amacrine cells.
Lens
Transparence focusing element of the eyes through which light passes after passing through the cornea any aqueous humor. The lens’ change in shape to focus at different distances is called accommodation.
Light-adapted sensitivity
Sensitivity of the eye when in the light-adapted state. Usually taken as the starting point for the dark adaptation curve because it is the sensitivity of the eyes just before the lights are turned off.
Lightness
Perception of reflectance. Usually objects with high reflectance are perceived as white and objects of low reflectance are perceived as gray or black.
Limulus
Primitive animal more the familiarly known as the horseshoe crab, which is been using experiments studying lateral inhibition.
Mach bands
Perception of a thin dark band on the dark side of a light-dark border and a thin light band on the light side of the border. These bands are an illusion because they occur even though corresponding intensity changes do not exist.
Macular degeneration
Clinical condition that causes degeneration of the macula, an area of the retina that includes the fovea and a small surrounding area.
Monochromatic light
Light that contains only a single wavelength.
Myopia
Inability to see distant objects clearly. Nearsightedness
Near point
Distance at which the lens can no longer accommodate enough to bring close objects into focus. Objects near the near point can be brought into focus only by corrective lenses.
Nearsightedness
Myopia
Neural convergence
Sentencing of a number of neurons onto one neuron.
Ommatidium
Structure in the eye of the limulus that contains a small lens, located directly over visual receptor. The Limulus eye is made up of hundreds of these ommatidia. The limulus eye has been used for research on lateral inhibition because its receptors are large enough so that stimulation can be applied to individual receptors.
Ospin
Protein part of the visual pigment molecule, to which the light-sensitive retinal molecule is attached.
Optic nerve
Bundle of nerve fibers that carry impulses from the retina to the lateral geniculate nucleus and other structures. Each optic nerve contains about 1 million getting me on cell fibers.
Outer segment
Part of the rod and cone visual receptors that contain the light-sensitive visual pigment molecules.
Peripheral retina
All of the retina except the fovea and a small area surrounding the fovea.
Presbyopia
Inability of the eye to accommodate due to a hardening of the lens and a weakening of the ciliary muscles. It occurs as people get older.
Pupil
Opening through which light reflected from objects in the environment enters eye.
Purkinje shift
Shift from cone spectral sensitivity to rod spectral sensitivity to text place during dark adaptation.
Refractive myopia
Myopia in which the cornea and-and/or the lens bends the light too much.
Retina
Complex network of cells that covers the inside back of the iPad D cells include the receptors, which generate an electrical signal in response to light, as well as the horizontal, bipolar, amacrine, and ganglion cells.
Retinal
Light-sensitive part of the visual pigment molecule. Retinal is attached to the protein molecule opsin to form the visual pigment.
Retinitis pigmentosa
Retinal disease that causes a gradual loss of vision.
Rod
Rod-shaped receptor in the retina primarily responsible for vision hello levels of illumination. The rod system is extremely sensitive in the dark but cannot resolve fine details.
Rod monochromat
Person who has a retina in which the only functioning receptors are rods.
Rod-cone break
Point on the dark adaptation curve at which vision shifts from Cohen vision to run vision.
Simultaneous contrast
Effect that occurs when surrounding one color with another changes the appearance of the surrounded color.
Spectral sensitivity
Sensitivity of visual receptors to different parts of the visual spectrum.
Spectral sensitivity curve
Function relating a subject’s sensitivity to light to the wavelength of the light. The spectral sensitivity curves for rod and cone vision indicate that the rods and cones are maximally sensitive at 500 nm and 560 nm, respectively.
Visible light
Band of electromagnetic energy that activates the visual system and that, therefore, can be perceived. For humans, visible light has wavelengths between 400 and 700 nm.
Visible acuity
Ability to resolve small details.
Visual pigment
Lights-sensitive molecule contained in the rod and cone outer segments. Reaction of this molecule to light results in the generation of an electrical response interceptors.
Visual pigment bleaching
Change in the color of visual pigment that occurs when visual pigment molecules are isomerized by exposure to light.
Visual pigment molecule
Light-sensitive molecules in the outer segments of the rod and cone visual receptors that are responsible for the transformation of light energy into electrical energy. The molecule consists of a large protein component come opsin and a small light-sensitive component called retinal.
Visual pigment regeneration
Occurs after the visual pigment’s two components – obsidian retinal – have become separated due to the action of light. We generation, which occurs in the dark, involves a rejoining of these two components to reform the visual pigment molecule. This process depends on enzymes located in the pigment epithelium.
Wavelength
For light energy, the distance between one peak of a lightwave the next peak.
White’s illusion
Display in which two rectangles are perceived as differing in lightness even though they both reflect the same amount of light and even though the rectangle that is perceived as lighter receives more lateral inhibition then the one perceived as darker.
