Term
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Definition
| Cornea and lens focus parallel light rays (originating from far objects) into a crisp image on the retina; 20/20 vision |
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Term
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Definition
| Nearsightedness; point of focus in front of the retina |
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Term
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Definition
| 1) cornea/lens bend light rays too much; 2) eyeball is longer than normal |
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Term
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Definition
| Farthest distance at which objects are in focus (objects beyond will appear blurred); the closer your far point, the more myopic you are |
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Term
| Myopic corrective lens formula |
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Definition
| diopters = -(1/far point) OR far point (m) = -(1/diopters); always negative; the lower the far point, the greater the diopters needed |
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Term
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Definition
| Farsightedness; point of focus behind the retina |
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Term
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Definition
| 1) cornea/lens don't bend light rays enough; 2) eyeball is shorter than normal |
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Term
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Definition
| Closest distance at which objects are in focus (closer objects appear blurred or doubled); the farther your near point, the more hyperopic you are |
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Term
| Hyperopic corrective lens formula |
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Definition
| diopters = 4-(1/near point) OR near point (m) = 1/(4-diopters); always positive and less than 4 diopters; the farther your near point, the greater the diopters needed |
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Term
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Definition
| For myopics, reduce corneal curvature (less focusing power); for hyperopics increase corneal curvature (more focusing power) |
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Term
| Photorefractive keratotomy (PRK) |
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Definition
| Sculpting of frontal surface; takes longer to heal, less used |
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Term
| Laser-assisted in situ keratomileusis (LASIK) |
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Definition
| Sculpting of surface underneath a frontal flap; heals faster, used more frequently |
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Term
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Definition
| Automatic change in focusing power of the lens; closer objects require greater accommodation, thicker lens |
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Term
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Definition
| Inability to accommodate with age (lens hardens, muscle weaken); form of hyperopia |
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Term
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Definition
| Misshapen cornea (not spherical) resulting in some orientations being clear, while others are blurred; can occur with either myopia and hyperopia |
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Term
| Qualifications for legal blindness |
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Definition
| 1) your better eye acuity is 20/200 or worse with correction OR 2) you have tunnel vision (central field is less than 20 degrees) |
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Term
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Definition
| 20 = how close you need to bring something to you to see what a normal sees; 200 = distance (in feet) at which a normal can see clearly; numerator is static, only denominator changes |
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Term
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Definition
| Transparent; results in 80% of the eye's focusing power (other 20% from lens) |
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Term
| Causes of corneal disease/injury |
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Definition
| Allergies, infections, injuries, etc. can cause 1) clouding/halos (fogginess), 2) decrease in acuity, 3) pain; treated with medication or corneal transplant |
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Term
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Definition
| Clouding of the lens; congenital, or caused by disease (secondary), injury (traumatic), or old age (senile) |
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Term
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Definition
| Lens removed whole OR phacoemulsification (ultrasound breaks up lens and is removed through incision); replaced with synthetic (intraocular) lens, which can no longer accommodate |
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Term
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Definition
| Unregulated sugar levels cause swelling and/or neovascularization, leading to leakage of blood into vitreous humor (blood vessels located on retina at back of eye) |
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Term
| Treatment of diabetic retinopathy (2) |
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Definition
| 1) laser photocagulation - damaging of multiple locations across retina so it requires less oxygen/blood; 2) vitrectomy - vitreous humor removed and replaced with saline |
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Term
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Definition
| Loss of central vision; caused by neovascularization (photocagulation can sometimes help) |
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Term
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Definition
| Retina separates from pigment epithelium, which is needed to produce photopigment in receptors; occurs spontaneously or from injury |
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Term
| Hereditary retina degeneration |
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Definition
| Retinitis pigmentosa is most common, with symptoms arising at young age; results in reduced vision at low light levels; affects peripheral, then central vision |
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Term
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Definition
| Optic nerve damage resulting from pressure cutting off circulation; normal/open angle more common and less severe, closed angle more rare and more severe |
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Term
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Definition
| Hole cut in iris to relieve pressure resulting from glaucoma |
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Term
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Definition
| Pattern of varying pressure; sound occurs when an object causes movement or vibrations of the surrounding medium |
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Term
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Definition
| Sinusoidal changes in air pressure over time; simple (single save wave), but less prevalent |
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Term
| Physical measures of sound (2) |
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Definition
| Amplitude - loudness (dB); frequency - pitch (Hz); 1 Hz = 1 cycle/sec |
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Term
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Definition
| Threshold of hearing; more sensitive to some frequencies than others; values below curve are inaudible and vice versa |
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Term
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Definition
| Fundamental frequency - determines pitch; second and third harmonics - determine instrumental characteristics; higher harmonics increase in frequency, but decrease in amplitude |
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Term
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Definition
| Part of the ear that is visible on the outside of the head |
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Term
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Definition
| Canal through which air vibrations travel from the environment to the tympanic membrane |
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Term
| Tympanic membrane (eardrum) |
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Definition
| Membrane at the end of the auditory canal that vibrates in response to vibrations of the air and transmits to the ossicles in the middle ear |
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Term
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Definition
| Three small bones in the middle ear (malleus, incus, and stapes) that transmit vibrations from the outer to the inner ear |
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Term
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Definition
| Small, membrane-covered hole in the cochlea that receives vibrations from the stapes |
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Term
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Definition
| Hole in the cochlea that moves in opposition to the oval window and allows movement of fluid and hair cells in the cochlea |
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Term
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Definition
| Snail-shaped, liquid-filled structure containing the structures of the inner ear |
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Term
| Scala vestibuli and timpani |
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Definition
| Located above and below the cochlear partition; terminate at the oval and round windows, respectively |
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Term
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Definition
| Separates scala vestibuli and tympani and contains the organ of Conti |
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Term
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Definition
| Membrane that stretches the length of the cochlea and controls the vibration of the cochlear partition |
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Term
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Definition
| Membrane that stretches the length of the cochlea and is located directly over the hair cells; vibrations of the cochlear partition cause the membrane to bend the hair cells by rubbing against them |
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Term
| Hair cells (inner and outer) |
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Definition
| Neurons in the cochlea that contain cilia (small hairs) that are displaced by vibration of the basilar membrane and fluids inside the inner ear; connect to auditory nerve fibers |
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Term
| Bekesy's place theory of hearing |
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Definition
| Theory that the frequency of a sound is indicated by the place along the organ of Conti at which nerve firing is the highest |
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Term
| Bekesy's place theory - traveling wave |
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Definition
| Base is 3-4x narrower, 100x stiffer than apex and takes more energy to get going; higher frequencies coded at base, lower at apex |
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Term
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Definition
| Ordered map of frequencies created by responding of neurons within auditory system structures; provides physiological support for place theory |
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Term
| Primary auditory cortex (A1) |
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Definition
| Involved in pitch perception; tonotopically mapped (like the cochlea) |
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Term
| What vs. Where in the auditory system |
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Definition
| Dorsal stream - sound localization ("what"); ventral stream - sound ID ("where") |
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Term
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Definition
| A change for the worse in either the structure or functioning of the auditory system |
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Term
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Definition
| Compromised ability to communicate or reduced quality of living due to hearing impairment |
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Term
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Definition
| Vibrations caused by sound stimulus are not conducted properly from the other ear to the inner ear |
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Term
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Definition
| Physical blockage (wax/objects), malformations (birth defects or injury), swelling from infection (swimmer's ear), ruptured tympanic membrane (ear drum) |
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Term
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Definition
| Middle ear infection, results in swelling and fluid; can lead to infection of mastoid bone or ear drum rupture if left untreated |
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Term
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Definition
| Growth of bone in mid-ear, causing stapes to become fixed and immovable; can be surgically removed |
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Term
| Sensorineural hearing loss |
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Definition
| Sounds not transduced properly due to damage of the hair cells in the inner ear |
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Term
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Definition
| Loss of sensitivity to high frequencies (e.g., speech perception) with age; can be alleviated with hearing aides |
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Term
| Noise-induced hearing loss |
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Definition
| Degeneration of hair cells resulting from loud, continuous noises or sudden explosive sounds with large impact (acoustic trauma) |
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Term
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Definition
| Amplify whatever frequencies you can't hear |
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Term
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Definition
| Electrodes inserted in cochlea stimulate auditory nerve fibers, if hair cells are damaged; frequencies applied at appropriate locations along the cochlea |
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Term
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Definition
| Ability to determine where a sound is coming from, either by a) the cues generated by the way sound interacts w/ the head/ears and/or b) the nature of the sound of the nature/environment |
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Term
| Defining location in 3-D space (3) |
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Definition
| 1) azimuth (horizontal); 2) elevation (vertical); 3) distance (depth) |
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Term
| General knowledge about sound localization |
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Definition
| 1) sound directly in front of us is most accurately localized; 2) sounds behind and to the side are less accurately localized; 3) localization not coded by location of receptors, it must be calculated |
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Term
| Factors affecting accuracy of localization |
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Definition
| The sound itself, environment, # of normally functioning ears, head movements, and other senses (like vision) |
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Term
| Inter-aural time difference (ITD) |
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Definition
| Binaural cue; difference in time it takes for a sound to reach the two ears; larger when sound comes from either side of the head |
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Term
| Inter-aural intensity difference (IID) |
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Definition
| Binaural cue; difference in sound pressure level (amplitude) reaching the two ears; only works at higher frequencies (>1000 Hz) |
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Term
| Spectral cues for elevation |
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Definition
| Monaural cue; the frequency spectrum of a sound once it reaches the ear is different from the original sound because of how the sound interacts w/ the head and pinnae |
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Term
| Measuring accuracy of sound localization (2) |
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Definition
| 1) free-field presentation - multiple external sound devices in the dark (more realistic); 2) headphone presentation - sources simulated via computer (more common, allows for precise timing and level controls) |
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Term
| Disadvantages of headphone presentation (2) |
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Definition
| Imprecise ITD and IID values can result in 1) internalization - sounds like coming from inside head or 2) externalization - sounds are perceived to originate from an external source outside head |
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Term
| Cues for judging distance (3) |
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Definition
| 1) sound level - pressure decreases w/ increasing distance (only useful for familiar sounds); 2) frequency - high frequencies absorbed by atmosphere; 3) movement parallax - closer objects move faster |
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Term
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Definition
| Part of inner ear; provides non-visual info about the orientation of the head and body which is used to maintain balance |
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Term
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Definition
| Hair cells that signal linear movement; includes utricle (horizontal movement) and saccule (vertical movement) |
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Term
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Definition
| Hair cells that signal rotational movement; turning the head laterally to the right procedures inertial fluid movement in the horizontally oriented semicircular cansls on either side of the head |
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Term
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Definition
| Movement of the head/body causes cupula to move and hair cells to bend |
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