The Visual System

Front 1

What cortex creates perception?

Visual memory? (which lobes)

Visual reflexes?

What controls circadian rhythm, general metabolic rate, hormonal function, mood?

Back 1

Front 2

How can you check visual memory?

Autonomic function?

Inner ear problem?

Back 2

Front 3

What is incoming light from the object of interest focused on? What is it refracted by? How is it variably refracted?

Projected onto what in the center of the macula?

Back 3

Front 4

Where is the fovea?

Back 4

At the center of the macula of the eye

Front 5

Identify:

Sclera, choroid, retina, blood vessels, fovea in macula, optic disk, optic nerve, ciliar muscle, suspensory ligament, lens, light, pupil, iris, conjunctiva, cornea, aqueous humor, virtreous humor, blood vessels

Back 5

Front 6

What is the purpose of sclera, choroid?

What maintain visual axis on fovea?

Back 6

Front 7

What is retinal blood flow provided by (20%)? What is the rest provided by?

Are there blood vessels in the fovea?

What is if called if blood vessels grow there?

Back 7

Front 8

List the layers of the retina.

Back 8

Front 9

What do the RPE cells do?

Where are the cell bodies of photoreceptors located? Where do their projections lie?

Where do they signal through?

What is the final layer of neurons in the retina?

Back 9

The pigment cells are the retinal pigmented epithelial cells (RPE). They provide a barrier to the retina from the choroid. Photoreceptors (cones and rods--named based on their shape) come in contact with the RPE.

The cell bodies of the photoreceptors are located in the outer nuclear layer, while their projections lie in the outer plexiform layer.

The photoreceptors signal through the outer plexiform layer to the bipolar cells, whose cell bodies are in the inner nuclear layer. The final layer of neurons in the retina are retinal ganglion cells (located in the ganglion cell layer). Once the visual object is transduced to the retinal ganglion cells, it will enter into the optic nerve and go to the brain.

Front 10

Review

Back 10

Front 11

What neurons help in convergence of the image from the millions of photoreceptors to hundreds of bipolar cells to tens of ganglion cells?

Back 11

Interneurons (horizontal cells and amacrine cells) help in convergence of the image from the millions of photoreceptors to hundreds of bipolar cells to tens of ganglion cells. Ultimately--the image will be sent through the ganglion cells to the optic nerve (optic nerve entry into the retina is the blind spot)

In the fovea, the outer segments are present, but the rest of the retinal layers are displaced radially to allow for minimal distortion of the image.

Front 12

What is the layer that separates choroid (vascular) from retina (neural)?

What pigment does it contain?

What are some functions?

Back 12

Main function = separation

2nd main function = eat rod outer segments every 10 days (becomes less effective as we age)

Front 13

Specific layers of the retina
RPE--main function is to separate the vascular choroid from the neural retina

Macular degeneration results when blood vessels damage the RPE and break through their barrier and grow into the macular region of the eye. Causes visual distortion of the image.

The 2nd main function of the RPE is to eat rod outer segments every 10 days. As we age--this becomes less effective. More proteins are left in the RPE, which can cause them to autofluoresce. This autofluorescence is called drusen and is a key factor in dry macular degeneration.

The melanin in the RPE help absorb some of the light that comes to the photoreceptors. When this absorption is reduced (blue-eyed people vs. brown eyed people), some think this may contribute to eye disease.

Back 13

Specific layers of the retina
RPE--main function is to separate the vascular choroid from the neural retina

Macular degeneration results when blood vessels damage the RPE and break through their barrier and grow into the macular region of the eye. Causes visual distortion of the image.

The 2nd main function of the RPE is to eat rod outer segments every 10 days. As we age--this becomes less effective. More proteins are left in the RPE, which can cause them to autofluoresce. This autofluorescence is called drusen and is a key factor in dry macular degeneration.

The melanin in the RPE help absorb some of the light that comes to the photoreceptors. When this absorption is reduced (blue-eyed people vs. brown eyed people), some think this may contribute to eye disease.

Front 14

What do rods process? Where it light detected and transduced? What is synaptic expansion called? What do rod outer segments undergo every 10 days?

Back 14

Front 15

What do cones process?

What are the three types and the wavelengths associated with each?

Back 15

Front 16

What color does each detect?

S cones, M cones, L cones?

What will be the effect if one type of cone is absent?

What chromosome carries M and L cones?

Back 16

Front 17

What is the purpose of photoreceptors?

What do both cones and rods undergo in response to light?

Back 17

Front 18

What is the pathway of visual phototransduction in rods?

Back 18

Light comes in => converts 11-cis-retinal to all-trans retinal => activation of rhodopsin (rod opsin) => GTP activated => activation of cGMP PDE => lowers cGMP enough to hyper polarize membrane and close sodium and calcium channels => VISUAL RESPONSE

Sodium and calcium accumulate in membrane => Ca2+ pumped out through exchanger => cGMP levels rise and depolarize membrane to pre-stimulus levels which re-opens channel

Rhodopsin dephosphorylated slowly => all-trans-retinal converted to 11-cis-retinal

Rhodopsin kinase re-phosphorylates rhodopsin => bound by arrestin to make inactive. If light stimulus occurs => arrestin removed by conversion of 11-cis-retinal to all-trans-retinal

Front 19

Where does phototransduction occur?

Back 19

Rods

Front 20

Back 20

Front 21

Where is the signal passed once photoreceptors have processed light?

Where to rod photoreceptors transduce their signal to?

What cells help converge the signals from multiple rod photoreceptors to fewer rod bipolar cells?

Back 21

Front 22

What type of ganglion cells predominant in the peripheral retina - receive most input from the rods? Where do they project?

Back 22

Front 23

Where are beta-ganglion cells found?

Where do they project? What are they responsive to?

Back 23

Front 24

Why does the rest of the signaling pathway (bipolar cells, ganglion cells) project radially away from the fovea?

Back 24

Front 25

Does convergence occur in the fovea?

Back 25

Front 26

Review

Back 26

Front 27

Why is the visual image reversed and inverted?

Where do ganglion cell axons decussate?

Where do optic tracts project?

Where do optic radiations carry geniculate fibers?

Where is the left visual field processed?

Back 27

Front 28

Review

Back 28

Front 29

Where does the M pathway originate and project to? What type of information?

Where does the P pathway originate and project to? What type of information?

Back 29

Front 30

What are all of these?

Back 30

Vision related diseases

Front 31

What disease does this patient have?

What are the light spots at the bottom of the image?

What is happening in the inferior region below the optic disc?

Back 31

Proliferative diabetic retinopathy

Blood vessel is damaged => edema occurring

Front 32

What are two major changes of DR?

Back 32

Front 33

What is shown here?

Back 33

A retinal image of a patient with macular degeneration

Hyperfluorescence and areas of non vascularity

Front 34

Compare AMD and DR:

Which involves choroid NV, retina NV?

Which is age induced? No age effect?

Which have some genetic components?

Which loses all vision? Lose central vision?

Back 34

Front 35

What are the two types of macular degeneration?

Which type sometimes has drusen, has vision loss, and progresses to both eyes?

Back 35

Front 36

There are 2 types of macular degeneration. Normally all people have a little drusen. When a patient has abnormal amounts of drusen and begins to lose vision--often in 1 eye--it is termed _____ macular degeneration or atrophic macular degeneration. This represents about ____% of the cases of macular degeneration. With visual aids, these people can continue to function

In the wet form (__% of cases)--the blood vessels grow into the macula and cause significant vision loss.

Back 36

There are 2 types of macular degeneration. Normally all people have a little drusen. When a patient has abnormal amounts of drusen and begins to lose vision--often in 1 eye--it is termed dry macular degeneration or atrophic macular degeneration. This represents about 90% of the cases of macular degeneration. With visual aids, these people can continue to function

In the wet form (10% of cases)--the blood vessels grow into the macula and cause significant vision loss.

Front 37

What are these all causes of?

Back 37

AMD

Biggest cause is age

The biggest cause of AMD is age. Smoking is also a big contributor. Some new research has shown some genetic predisposition due to altered inflammatory responses.

In the last 5 years--patients with AMD have hope. Using intravitreal injections (about monthly)--they can get a drug that blocks the vascular growth. It does not restore vision in most patients, but it often helps them maintain what vision they have. Eventually they will still lose vision, but the drugs are much better than previous options.