Visual Processing: The Eye And Retina

Front 1

Visual Field

Back 1

Area in space perceived when the eyes are in a fixed, static position looking straight ahead

Front 2

Monocular visual field

Back 2

space visible to one eye. the nose prevents the field of the right eye from covering 180 degrees in the horizontal plane

Front 3

Perimetry testing

Back 3

provides a detailed map of the visual field--the nose, brow and cheeks occlude the view of the most nasal, superior and inferior areas

Front 4

Blind Spot

Back 4

small area in which objects cannot be viewed--located within the temporal hemifield

Front 5

Binocular Field

Back 5

Area of overlap of the visual field of one eye with that of the opposite eye

Front 6

What is most commonly used for the clinical examination of the visual fields?

Back 6

Confrontation Test

Front 7

Visual Acuity

Back 7

Ability to detect and recognize small objects visually--depends on refractory (focusing) power of the eye's lens system and the cytoarchitecture of the retina. Measured under high illumination and is the smallest size of a dark object that can be correctly identified (snell eye chart)

Front 8

Ishihara Chart

Back 8

Tests color vision--spots of different colors are spatially organized to form numbers that differ for normal and color blind eyes

Front 9

Color Blindness

Back 9

most common form is red-green color blindness--result from an absent or defective gene responsible for producing red or green photopigment. X linked therefore more common in MALES

Front 10

Visual Field Center

Back 10

Operates best under high illumination, greatest acuity and color sensitivity. ten times better than field periphery, photopic (light adapted) subsystem

Front 11

Peripheral Visual Field

Back 11

sensitive to dim light, best under low illumination, little color sensitivity, poor spatial acuity, Scotopic (dark adapted) subsystem

Front 12

Binocular Fusion

Back 12

Process of producing a single image from the two disparate monocular images (holding a pencil at arms length)

Front 13

Amblyopia

Back 13

a result of uncorrected strabismus--image from the deviant eye (from normal position) is no longer represented at cortical leves of nervous system--result is functional blindness in one eye and poor depth perception

Front 14

The _______ the curvature of the lens surface the ________ refractive power and the _______ (closer/further) is the focused image to the lens

Back 14

greater;greater;closer

Front 15

The image formed is ____(smaller/larger) than the object viewed, inverted, and left right reversed.

Back 15

smaller

Front 16

The ______(nearer/further) the object of view, the _____(greater/lesser) the angle of incidence of light rays on the cornea, and the ______(greater/lesser) the refractive power rquired to focus the light rays on the retina.

Back 16

nearer; greater; greater

Front 17

T/F: The cornea has a fixed refractive power

Back 17

True: it cannot change its shape

Front 18

Accommodation

Back 18

change in refractive properties of the eye by altering the tension of zonules on the elastic lens capsule

Front 19

Normal eye under resting (distant vision) conditions

Back 19

-ciliary mm. are relaxed
-zonnules are under tension
-lens is flattened which reduces the refractive power of the lens to focus on distant objects

Front 20

Normal eye under closer conditions

Back 20

- accommodation occurs to affect "near vision"
-ciliary mm. contract pulling the ciliary processes toward the lens
-tension released from zonnules and lens capsule
-lens becomes spherical which increases the lens refractive power to focus on near objects

Front 21

What is the retina derived from?

Back 21

Neural tube

Front 22

Retinal pigment epithelium

Back 22

dark pigments withing the retinal pigment epithelium and choroid coat function to absorb light passing through the receptor layer, thus reducing light scatter and image distorition within the eye.

Front 23

Five types of neurons in neural retina

Back 23

-visual receptor cells (rods and cones)
-horizontal cells
-bipolar cells
-amacrine cells
-retinal ganglion cells

Front 24

Layers of retina

Back 24

retinal pigment epithelium (outer)
receptor layer
outer nuclear layer
outer plexiform layer
inner nuclear layer
inner plexiform layer
retinal ganglion
optic nervce

Front 25

Fovea

Back 25

where the image of the central visual field center is focused; retina consists of fewer laers here thereby minimizing obstacles to forming a clear image on the fovea

Front 26

What forms the optic disc?

Back 26

retinal ganglion cell axons that are exiting the retina; it is located nasal to the fovea; this region is devoid of receptor cells and composed by the optic nerve layer---i.e. blind spot

Front 27

Rods

Back 27

outer segment disks contain photopigment rhodopsin which absorbs wide bandwidth of light; respond best to white light; more sensitive at low levels of illumination

Front 28

Cones

Back 28

differ from rods in the color of light their photopigments absorb (either red, green or blue)

Front 29

Scotopic, dark-adapted system

Back 29

Rods: rhodopsin is borken down when exposed to light bandwidth, reacts at lower levels, longer outer segments, more outer segment disks, and more photopigment; more sensitive to light, dominate in PERIPHERAL retina (color insensitive, poor acuity, sens to low levels illum)

Front 30

Phototopic visual process

Back 30

Cones: chromatic photopigments, color sensitive, less sens to light and need high illum, concnetrated in fovea where image of central visual field is projected, fovea responsible for phototopic vision (high acuity and color vision) in CVF

Front 31

T/F: Cones do not respond to white light

Back 31

FALSE, white light contains all the wavelengths of visible light

Front 32

Light adaptation

Back 32

going from dark room to light--allows the cone response to dominate over rod responses at high illumination

Front 33

The direct pathway for the transmission of visual info fom eye to brain includes only ___, ___, and ____.

Back 33

receptor cell, bipolar cell, ganglion cell

Front 34

Horizontal Cells

Back 34

lateral connections only; modulate synaptic activity of receptor cells and indirectly affect the transmission of visual info by bipolar cells; synapse with bipolar and photoreceptor cells in outer plexiform layer

Front 35

Amacrine Cells

Back 35

modulate the synaptic activity of the retinal bi[polar and ganglion cells thereby affecting the transmission of visual info by ganglion cells; differ from horizontal cells in providing vertical inks between bipolar and ganglion cells.

Front 36

Bipolar cells

Back 36

125 million photoreceptor cells synapse with 10 million bipolar cells in outer plexiform layer. respond to glutamate released by photoreceptor cells

Front 37

T/F: Bipolar Cells generate action potentials

Back 37

False; they respond to photoreceptor release of glutamate with graded potentials (by hyperpolarizing or depolarizing)

Front 38

Off bipolar cells

Back 38

depolarized by glutamate when the photoreceptors that synapse with it are in the dark (i.e. when light is turned off); detect dark objects in a lighter background

Front 39

On bipolar cells

Back 39

hyperpolarized by glutamate (which is released by photoreceptor cell in the dark), depolarized when light is turned on, and detect light objects in a darker background

Front 40

Cone-bipolar cell

Back 40

synapses with atleast one cone; receptive fields are extremely small and color sensitive; may be on-type or off type (hyperpolarized or depolarized by glutamate)

Front 41

Rod-bipolar cell

Back 41

make synaptic contact with fifty or more rod receptor cells; large receptive field and color insensitive; all depolarized by light by a decrease in glutamate from rods-->on type bipolar only

Front 42

Surround Effect

Back 42

produced by horizontal cells, enhances brightness contrasts to produce sharper images, to make an object appear brighter or darker and to maintain contrasts under different illum levels

Front 43

Ganglion cell response properties

Back 43

Read pg 14 of syllabus

Front 44

Most bipolar cells release _____ which is ______ to most ganglion cells.

Back 44

glutamate; excitatory

Front 45

Retinal ganglion cells provide info important for detecting the _____ and _____ of objects

Back 45

shape and movement

Front 46

Type P retinal ganglion cells

Back 46

-color sensitive object detectors
-outnumber M cells 100:1
-make synaptic contact with cone bipolars that are innervated by cone receptors in fovea
-small concentric receptive field
-slowly adapting reponse
-weak reponses to stimuli that move across receptive field

Front 47

Type M retinal ganglion cells

Back 47

-color insensitive motion detections
-much larger than P cells
-synapses with many bipolar cells
-large concentric receptive field
-rapidly adapting reponse
-responds maximally with high discharge rates to stimuli moving across its receptive field

Front 48

Where do most axons of ganglion cells terminate?

Back 48

lateral geniculate nucleus of thalamus

Front 49

_____(low/high) convergence of cones to cone bipolar cells and _____(low/high) convergence of cone bipolar cells to P retinal cells.

Back 49

low and low; produces high visual acuity in central visual field. opposite for rods