Vision Flashcards by Venice Camille Patricio

The study of the properties and behavior of light and its interaction with matter

Optics

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True or False:

The direction in which light rays travel is always perpendicular to the plane of the waveform

True

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Path of light as it enters the edge of concave lens
A. Convergence
B. Divergence

B. Divergence

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Path of light as it enters the edge of convex lens
A. Convergence
B. Divergence

A. Convergence

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Towards the edge of the lens, light rays strike a more angulated surface. The outer rays bend more towards the center causing the CONVERGENCE of all light rays and will meet through a single point known as :

focal point

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True or False:

The light rays entering the center of the concave lens will refract

False:
The light rays entering the center of the lens will strike an interface that is perpendicular to the beam (do not refract)

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Distance at which the parallel light rays converge to a common focal point.

Focal length

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True or False:

Increase in lens convexity will increase the ability to bend the light

True

↑ in lens convexity = ↑ ability to bend light rays

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The ability of a lens to bend light rays is known as the:

refractive power of the lens

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An increase in accommodation of the eye will ___________ the refractive power of the lens
A. Increase
B. Decrease
C. Not affect

A. Increase

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Which structures keep the lens flat under resting conditions?

Suspensory ligaments

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2 types of ciliary muscle fibers that function for accommodation

Meridional fibers

Circular fibers

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Ciliary muscle fibers that extend anteriorly from the peripheral end of the suspensory ligament to the corneoscleral junction

Meridional fibers

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To which direction do the meridional fibers of the ciliary muscle pull the sensory ligaments to release their tension on the lens

forward and medially towards the cornea

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Contraction of the ciliary muscle will result to:
A. Increase in tension in the lens
B. Increased tension on suspensory ligaments
C. Increased spherical shape of the lens

C. More spherical shape of the lens

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Accommodation is controlled almost entirely by the:
A. SNS
B. PNS
C. Edinger-Westphal nucleus
D. Somatic nervous system

B. PNS

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Looking at far objects will cause which of the following on the ciliary muscle, suspensory ligaments and lens:
A. relax, tighten, thicken
B. contract, tighten, thicken
C. relax, tighten, thin
D. relax, tighten, thicken

C. Relax, tighten, thin

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Depth of focus will be _____ with small apertures:
A. Greater
B. Lesser
C. Not change

A. Greater

as this allows the passage of all rays through the center of the lens and most central rays are always in focus

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T/F:

A large pupillary diameter will result to a blurred image

T due to lesser depth of focus

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Decreased ability of the lens to change shape with aging (non-accommodating lens)

Presbyopia

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T/F: Presbyopia result to the inability to accommodate for near vision only

F: both near and far vision

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Correction for presbyopia

Bifocal lenses with upper segment for far vision and the lower segment for near vision

Berne: convex lens

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State of refraction when parallel rays from distant objects are in sharp focus on the retina when the ciliary muscle is relaxed or when the lens is flat

Emmetropia

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Error of refraction that occurs with weak lens system

Hyperopia (Far-sightedness)

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Error of refraction that occurs with short eyeballs

Hyperopia

T/F: | Focal length is too long with hyperopia

Lens Correction for hyperopia

Convex lens

Error of refraction the occurs when eyeballs are too long

Myopia (near-sightedeness)

Error of refraction that occurs when lens system is too strong

Myopia

Error of refraction that occurs with too high refractive power

Myopia

T/F: | Focal length is too short with myopia

True

Corrective lens for myopia

Concave lens to decrease the refracting power of the lens

Condition wherein light fails to come at a single point of focus on the retina because of the differences in the curvatures along the plane of the cornea or lens itself

Astigmatism

Lenses used to correct astigmatism

Spherical or cylindrical lens

What are initially determined prior to correction of astigmatism?

Axis of defects and strength of the lens

``` What causes the problem in astigmatism? A. accommodation of lens B. refractive power of lens C. shape of cornea or lens D. length of eyeball ```

C. shape of cornea or lens

Condition of cloudy or opaque areas of the lens due to the denaturation of the proteins of the lens fibers resulting to their coagulation

cataract

Minimal distance between two points at which the eye can distinguish them from each other

Visual acuity

Total diameter of retinal spot (spot of light)

11μm

The average diameter of cones in the fovea of the retina, the central part where vision is most highly developed, is about:

1.5μm

Test for far vision

Snellen test

Test for near vision

Jaeger test

How far is the Snell chart placed when testing for visual acuity?

20 feet away

How far is the Jaeger chart placed when testing?

14 inches

Visual acuity is expressed as the fraction between:

one's visual acuity over normal visual acuity Snellen 20/20 Jaeger 14/14

Intraocular fluid posterior to the lens

Vitreous humor

All aqueous humor are secreted by the:

ciliary processes

A thin-walled vein that extends circumferentially all the way around the eye, and has porous endothelial membrane allowing passage of large protein molecules and small particulate matter up to the size of red blood cells form the anterior chamber

Canal of Schlemm

Normal intraocular pressure

15mmHg or | 12-20 mmHg

Debris within the eye are cleared off from the trabeculae via:

Phagocytic cells located at the surface of the trabeculae Interstitial gel on top of the canal of Schlemm containing reticuloendothelial cells

Condition that leads to high intraocular pressure, the principal cause of blindness

Glaucoma | 60-70mmHg

In most cases of glaucoma, the cause of abnormally high pressure is:

Increased resistance to fluid outflow

The fine fibrillar network holding the vitreous humor is composed primarily of greatly elongated _________ molecules

proteoglycan

Component of the retina that is responsible for crude vision

Rods

T/F: | Light passing through the several layers of retina significantly affects visual acuity

True

In the absence of this retinal layer, contrast between light and dark will not be appreciated

Pigment layer

This precursor of photopigments is stored by the outermost layer of the retina

Vitamin A

Small area at the center of the macula lutea (small yellowish area for central vision)

Fovea

T/F: | Foveal cones have fatter cones

False because | Foveal cones have especially long and slender bodies

Which segment of photoreceptors store photochemicals?

Outer segment

The greater sensitivity of the rods to light is due to its greater:

(greater) visual pigment density

True or False: Cones contain stacks of membrane discs that float freely in the outer segment (completely disconnected from the plasma membrane)

True

Which segment of the photoreceptors contains the mitochondria?

Inner segment

Which segment of the photoreceptors connects with the horizontal and bipolar cells?

Synaptic segment

AKA visual purple

Rhodopsin

Composition of Rhodopsin

Scotopsin and 11-cis retinal (retinene)

``` Which of the following is vitamin A? A. 11-cis retinol B. 11-cis retinal C. all-trans retinol D. all-trans retinal ```

C. all-trans retinol

Decomposition sequence of Rhodopsin after exposure to light energy: A. Bartho-, Lumi-, Meta- I, Metarhodopsin II B. Lumi-, Bartho-, Meta- I, Metarhodopsin II C. Bartho-, Lumi-, Meta- II, Metarhodopsin I D. Lumi-, Bartho-, Meta- II, Metarhodopsin I

A. 11-cis retinal (retinene) + scotopsin → Rhodopsin → Barthorhodopsin → Lumirhodopsin → Metarhodopsin I → Metarhodopsin II → scotopsin + all-trans retinal

``` Photoactivation of electrons in the retinal portion of the rhodopsin changes the conformation of: A. Rhodopsin to all-trans retinal B. 11-cis retinal to all-trans retinal C. Rhodopsin to all-trans retinol D. 11-cis retinal to Rhodopsin ```

B. 11-cis retinal to all-trans retinal

The product of partial splitting of scotopsin and all-trans retinal

Barthorhodopsin

This is the activated rhodopsin

Metarhodopsin II

Enzyme for the first step of reformation of rhodopsin

Retinal isomerase | Converts all-trans retinal to 11-cis retinal; energy requiring

``` In normal dark conditions, rods have: A. Increased electronegativity B. Reduced electronegativity C. Low levels of cGMP D. High levels of 5'-GMP ```

B. Reduced electronegativity

This form of rhodopsin functions as an enzyme that activates the G-protein Transducin upon exposure to light

Metarhodopsin II

This enzyme inactivates Metarhodopsin II

Rhodopsin Kinase

Color pigments which may be present in cones:

Red, Blue, Green

Which of the following happens with Light Adaptation? A. Opsin is converted back to light-sensitive pigments B. Retinal is converted back to light-sensitive pigments C. Retinal is converted to Vitamin A D. Increased sensitivity to light

C. Retinal is converted to Vitamin A

Which of the following happens with Dark adaptation? A. Photochemicals are reduced to retinals and opsin B. Most of the retinal is converted to vitamin A C. Reduced light-sensitivity D. Opsins and retinal is converted to light-sensitive pigments

D. Opsins and retinal is converted to light-sensitive pigments

Neural cells that provides lateral inhibition that enhance visual contrast

Horizontal cells

These cells provides a second mechanism for lateral inhibition

Bipolar cells

These cells transmit signals vertically to the inner plexiform layer

Bipolar cells

Horizontal cells transmit signals horizontally in which layer of the retina?

Outer plexiform layer

Amacrine cells signal directly to which cells?

ganglion cells

These cells detect intensity of illumination

Amacrine cells

These cells detect changes in direction of light

Amacrine cells

These cells transmit signals from the retina through the optic nerve into the brain

Ganglion cells

In which location of the retina do ganglion cells have greater sensitivity to weak light

Peripheral retina

The following occurs in the peripheral ganglion cells, except: A. Number of optic fibers is almost exactly equal to the number of cones B. As many as 200 rods converge on a single optic nerve fiber C. Summation of rod signals gives more intense stimulation to the ganglion cells D. Greater sensitivity to weak light

A. *Happens in the central retinal ganglion cells*]: number of optic fibers is almost exactly equal to the number of cones responsible for high degree of visual acuity

Most numerous of the | Ganglion cells

X cells

Fewest and of largest diameter ganglion cells

Y cells

Ganglion cells with slow velocity of signal transmission that are also sensitive to directional movement in the field of vision

W cells

Ganglion cells that respond to rapid changes in the visual image

Y cells Transmits signals FAST at 50m/sec

Structure that transmit visual signals from the dorsolateral geniculate nucleus of the thalamus to the primary visual cortex

Optic radiation

Retinal layers that receive signals from the lateral half of the ipsilateral retina

Layers II, III, V Photoreceptor, Outer nuclear and Inner nuclear layers

Retinal layers that receive signals from medial half of the retina of the opposite eye

Layers I, IV, VI | Pigmented, Outer plexiform and Inner plexiform layers

Magnocellular layers of the retina

Layers I and II = Y ganglion cells

The parvocellular layers receive input from which type of ganglion cell?

X cells = color

These control the transmission of signals to the visual cortex

Corticofugal fibers of the Occipital lobe | Reticular layer of the mesencephalon

Cortical terminus of Direct Visual Signals

Primary visual cortex (B17, aka visual area I or Striate cortex

The larger area of the primary visual cortex represents the ______ or the centermost portion of the retina

macula

``` Signals coming from the peripheral portion of the retina terminate at the _____ aspect of the primary visual cortex A. macular B. medial C. lateral D. inferior ```

B. medial

Visual cortical area for analysis of visual meaning

Secondary Visual cortex or Visual association area (B18 or visual area II)

``` The visual association area lies ____ to the primary visual cortex A. lateral B. anterior C. inferior D. superior E. AOTA ```

E. AOTA

This mechanism is controlled by a cortical field located bilaterally in the premotor cortical region of the frontal lobes

Voluntary fixation mechanism

Damage in the secondary visual cortex will result in difficulty keeping the eyes still and inability to direct the eye towards a desired object. This is the loss of:

Involuntary fixation mechanism

Parasympathetic nucleus for autonomic control of pupillary aperture

Edinger-Westphal Nucleus

Which cells of the T1 segment have sympathetic control of pupillary aperture?

Intermediolateral horn cells

Muscles innervated by the ciliary ganglion

Ciliary muscle | Sphincter pupillae

Muscles innervated by the Intermediolateral horn cells of T1 to control the eyes

Radial fibers of the dilator pupillae | Extraocular muscles

Nuclei that elicit reflex movements of the eyes to focus on objects of importance and to activate the pupillary light reflex

Pretectal nuclei

Area of the older brain for control of rapid directional movements of the two eyes

Superior Colliculi

Visual nuclei that presumably help control some of the body’s behavioral functions.

VPL