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54 Cards in this Set

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What are the anterior and posterior chambers of the eye?

Primary aqueous humor filled chambers in front of the lens

What is the vitreous body of the eye?

Chamber located behind the lens filled with vitreous humor

How are images in the visual field focused?

Through the cornea, pupil of the iris, lens then on the retina.

What is the retina?

Neural part of the eye that converts a visual image into nerve action potentials through an energy requiring chemical process

Describe the layers of the retina

7-10 layers of neuroglial cells and cell processes

How are images transduced?

Photoreceptors - divided into rods and cones

Describe the function of photoreceptors

Contain pigments that can be altered very rapidly by light to generate a depol of a nerve cell membrane

Describe Rods

Approx. 130 million per eye Sensitive to dim light and cannot differentiate color Rhodospin (Vit A)

What can result if there is a loss of rods? \

Night blindness - "legally blind"


-Can be due to Vit A insufficiency

Describe Cones

Approx. 7 million per eye Sensative to different frequencies associated with red,blue, green :lodopsins

How is color perceived

As combinations of different cone types activation

What can occur in the absence of one of the photopigments of cones?

Color blindness - usually red and green

Why is color blindness more common in men?

Because genes encoding the red or green pigments is on the X chromosome

Where are cones most numerous?

The Fovea

What is the Fovea?

Small depression in the retina in whch the primary visual image is focused

In primates what makes up most of the fovea?

Cones .

What is the Fovea?

Region of the eye with the highest visual acuity

What retinal layers are present in the fovea?

Photoreceptors containing cones

True or false: Retinal vessels are present on the fovea

False: Retinal Vessels are ABSENT on the fovea

What is the Macula

Area surrounding the fovea that has a yellowish appearance due to the presence of yellow pigment

What may result in severe visual impairment (in relation to the macula)

Macular Degeneration - Unknown Origin

How is visual information received?

Photoreceptors generate electrical potentials that are processed in the retina and finallt conducted out of the eye as action potentials by Retinal Ganglion Cells

What do the axons of the Retinal ganglion cells form?

Optic nerve, chiasm, and optic tracts

What is the Optic disc

Papilla




Point at which retinal ganglion cell axons leave the eye and retinal blood vessels enter.

What forms the blind spot in the visual field?

Lack of photo receptors in the Optic disc

Why is the optic disc examined after head trauma?

It can indicate the presence of increased intracranial pressure from hydrocephalus

What is Papilledema

Blockage of flow from retinal veins leading to swelling of the optic nerve head.



What is Glaucoma

Increased pressure from the fluid chambers of the eyes

What is a visual fields

What you can or cannot see with each eye

What is Perimerty

Quantitation of visual field

How is Perimetry testing done?

Usually done with a machine that shows brief flashes of light at different points within the visual field as the patient looks at a central point.

How are visual fields usually represented?

Graphically as two circles.




Blind spot and macula may or may not be shown

How do axons from the retinal ganglion cells travel from the retina?

Through the optic nerve to the optic chiasm.

At the optic chasm where do the axons of the retinal ganglion cells travel?

Half carry info from the retina of each eye cross, thereby dividing the visual field into halves - vertically

Which hemispheres does each visual field get routed to?

Right half of visual field to the left hemisphere


Left half of visual field to the right hemisphere

What is binocular vision

Depth Perception

What creates depth perception?

The division of the visual fields into left and right halves and the fact that the visual fields from each eye overlap

How is a three dimensional perception of space created?

By comparing the overlapping images in the occipital lobe

How does the optic chiasm axons contact the lateral geniculate nucleus of the thalamus

Travels around the brainstem near the crus cerebri

What does the lateral geniculate nucleus do?

Puts together the entire left or right visual field from both eyes

What is the geniculo-calcarine tract?

Where the lateral geniculate neurons project to primary visual cortex in the occipital lobe

Where is the primary visual cortex located?

On either side of the calcarine sulcus of the occipital lobe




Posterior cerebral artery territory)

How is the macula and retina respresented

Posteriorly and the surrounding retina more anteriorly

Vision loss in one eye due to

Lesion of the optic nerve

Vision loss in both eyes

Lesions at or beyond the chiasm

Lesion including the primary visual cortex will produce

Contralateral hemianopsia with macular sparing

Why is the macula spared with a lesion of the primary visual cortex?

Because of some collateral circulation from the middle cerebral arteries

What is the pupillary light reflex

Basic clinical test for visual function, where a light is shined in one eye and observed for pupillary constriction

What is involved in the pupillary light refelx

Ciliary ganglion, oculomotor nerve, optic nerve and some nuclei in the brainstem near the superior colliculus of the tectum.

What can cause the disruption of the pupillary light reflex?

Disruption of any of the pathways involved in the reflex

What occurs to the light reflex if the optic nerve is disrupted

A light shined into the blind eye will not produce constriction, but will when shined into the normal eye




-Swinging the light back to the blind eye will then result in dilation of both pupils

What is the most common impairment of the pupilary reaction to light?

Deteriorating conscious level after head injury

When will the uninjured side eye still respond to light reflex?

As long as the optic pathway is intact

What controls pupillary dilation?

Sympathetic nervous system