Full transcript
0:07hi Ninja nerds in this video we're going
0:09to talk about specifically the visual
0:11pathway so we're going to take how the
0:13light hits the retina and we're going to
0:15take it through the optic nerve and all
0:16the other different process if you guys
0:17have already watched our video on the
0:19photo transduction Cascade that's going
0:20to be very very important that you do
0:22that before we get into this visual
0:24pathway because we already talked about
0:25exactly how those light rays got
0:27converted into chemical changes and then
0:28electrical changes and how they went
0:30down the axons of the gangling cells
0:31which basically made up the optic nerve
0:34all right so
0:36now we're going to have two eyeballs
0:39right this is the we're going to say
0:40this is the left
0:44eyeball and this is the
0:46right
0:49eyeball okay now first things first what
0:54I want us to try to imagine here we're
0:55going to put a lot of different concepts
0:56together when you guys are looking you
0:59guys are like looking at anything around
1:01you we H our eyes are so amazing that
1:04they can pick up different types of
1:07visual Fields so for
1:09example this is the right visual field
1:12or the right eyes visual field and this
1:14is the left eyes visual field okay so
1:17what is this one right here this is the
1:19right
1:21eyes visual
1:25field and this one over here is the left
1:29eyes
1:30visual
1:32field okay now within the visual field
1:36you have two different components of
1:39this visual field we're going to say
1:41this is the nasal so since your you'd
1:43have your Honker right there pretend
1:45this is your nose Okay so pretend this
1:47structure here is your nose Okay since
1:50this is the nose these two structures
1:52that are near the nasal region this is
1:54the nasal component of the visual field
1:57all right so this is the nasal comp
1:59opponent of the visual field and then
2:02this one over here would be near the
2:04temple so this is the
2:07temporal component of the visual field
2:09and this over here is going to be the
2:12temporal component of the visual field
2:15okay now to make it easy though now that
2:20we know that this is what it is it's
2:21nasal and the temporals these words are
2:24going to get interchanged a lot so I do
2:26not want to confuse you guys so what I'm
2:28going to do is for this sake of it is
2:31I'm going to switch
2:33nasal and since this is the right visual
2:36field this is what gets confusing the
2:38right visual field has a left visual
2:41field and a right visual field okay so
2:44the right eye has a left visual field
2:47and a right visual field so we're going
2:49to say this is the left visual
2:52field and this is the right visual field
2:56okay so I just want to make it as simple
2:57as I possibly can here this whole right
3:00eye is going to have two Fields it's
3:02going to have the right visual field and
3:04left visual field same thing this left
3:06eye is going to have two visual
3:09Fields it's going to have
3:12a left visual
3:14field and a right visual field okay
3:19simple as that now we're going to be
3:21able to kind of do this a lot easier now
3:23so instead of using the words nasal and
3:24temporal but understand those words
3:26because it's going to be important in
3:28lesions okay let's say first off when
3:31we're looking out let's say that this
3:34part of the retina there's two parts of
3:36the retina so this is the right eye this
3:39part of the retina is closest to the
3:41temple or the right Temple right so
3:43we're going to call this part of the
3:45retina we're going to call this the
3:51temporal
3:54Hemi
3:56retina okay that's a temporal hemir
3:59retina
4:00now here's what gets really funky the
4:03temporal hemir retina is receiving light
4:07rays from the left visual field okay so
4:12from here this part here this left
4:15visual field is hitting this part of the
4:18retina okay so if light rays from the
4:21left visual field are hitting this part
4:23of the retina the temporal H retina but
4:28then the the what is this one this one
4:31is close to the actual nose so since
4:34it's close to the nose this is called
4:36the
4:37nasal right
4:41Hemi
4:42retina this is called the nasal hemir
4:44retina and this is called the temporal
4:46hemir retina the nasal hemir retina is
4:49receiving light from
4:52the right visual field so the nasal hem
4:55retina is getting hit with light from
4:57the right visual field all right so just
5:00to make sure we're clear left visual
5:01field hits the temporal hemir retina and
5:04the right visual field hits the nasal
5:06hemir retina sweet deal same thing would
5:08happen up here what would this one be
5:10this one right here would be the
5:11temporal hemir
5:15retina I'm going to put HR
5:17here and this right up here is going to
5:20be the
5:22nasal hemir retina okay and same thing
5:26nasal hemir retina is going to be
5:28receiving visual field from left visual
5:31field so it's going to be getting it
5:32from the left visual field and then the
5:34temporal hemir retina on the left
5:36eyeball is going to be receiving it from
5:39the right visual
5:41field okay now that we're done with that
5:44what happens with these fibers here's
5:47what I want you to remember anything
5:49from the right goes to the
5:51left anything with a left goes to the
5:55right that's it anything that's coming
5:58from the left okay well this temporal
6:01hemir retin this is on the right eyeball
6:05okay so this is the right eyeball it's
6:06picking up information from the left
6:08visual field well anything from the left
6:11has to go to the right oh so these
6:12should stay on the same side then so
6:14these fibers right here they should not
6:16go and cross over to the other side they
6:18should stay on the same side so they're
6:20going to come down the optic nerve and
6:22you know what happens the two optic
6:25nerves actually come together they come
6:27together and form this big old structure
6:29that you kind of see right here I'm
6:30actually not going to do it in brown
6:32here because I'm going to use this brown
6:33a lot I'm just going to say here that
6:37this point here where the two optic
6:38nerves are connected all of this part
6:40right here this whole thing is called
6:42the
6:44optic
6:46kiasma and the optic Asma is where the
6:49right optic nerve and the left optic
6:51nerve come together right near the
6:52pituitary gland so this is right near
6:54the pituitary gland okay now what
6:58happens here the fibers from the
7:01temporal hemiretina which is receiving
7:03it from the left visual field we said
7:04anything from the left visual field will
7:06go to the right eye okay so this is
7:09going to cross I mean it's not going to
7:11cross it's going to stay on the same
7:12side so it's going to come down the
7:13right optic nerve where the optic Asma
7:15is it's not going to cross it's going to
7:17stay on the same side and it's going to
7:18move down this structure right here
7:20which is called the optic tract and
7:23we're going to stop right there okay so
7:25what is this structure right here this
7:27long tube likee structure here this
7:29whole tube like structure here is called
7:31the
7:32optic tract so this would be the right
7:35optic tract what do you think this one
7:36is this is the
7:38left optic tract and this is the optic
7:42Asma okay now let's follow this nasal
7:45hemor retina well the nasal hemor retina
7:48is receiving information from the right
7:51visual field well anything from the
7:53right goes to the left so this has got a
7:56cross so these fibers from the nasal
7:58hemir retina it's going to come through
8:00the optic nerve the right optic nerve
8:02and it's going to cross at the optic
8:04Asma and go over here to the opposite
8:09side it's going to come over to what
8:10optic tract it's going to come over here
8:12to the left optic tract and it's going
8:14to come right to there and that's what
8:15we'll stop at that point okay now that
8:19we understand this this should be a lot
8:20easier now let's do this one nasal Hema
8:24is receiving what it's getting hit from
8:26the left visual field well if it's
8:29receiving information from the left
8:30visual field anything from the left has
8:32to go to the right oh okay well this is
8:34on the left that means it has to cross
8:35over here so it'll come down the left
8:38optic nerve but then instead of going on
8:40the same side it's going to cross over
8:42it's going to become contralateral right
8:44and these fibers are going to come over
8:47here and they're going to move all the
8:51way over here on this side and come
8:54right
8:56there okay so all the things that are
8:58coming from the left visual ual field on
9:00the left nasal hemir Rey is going to be
9:02coming from the left visual field is
9:04going to be taking that information on
9:05the right optic tract and into this area
9:07that we're going to talk about in a
9:08second let's keep
9:11going temporal Hemy it's going to be
9:14receiving information from the right
9:16visual field right of the left eye so
9:18it's going to be receiving from the
9:18right visual field when anything from
9:20the right goes to the left we're already
9:22on the left side of the eye let's just
9:23keep it ipsilateral so these fibers here
9:26are going to come down the left optic
9:28nerve it's not going to cross at the
9:30optic chasma it's going to stay on the
9:32same side and move down the left optic
9:34tract and into this area right here okay
9:37so these are your fibers that are
9:39crossing and these are the ipsilateral
9:42fibers so what are these fibers right
9:43here called these fiber here that are
9:45staying on the same side are your
9:47ipsilateral fibers these are the
9:49ipsilateral
9:52fibers and these fibers here that are
9:54crossing are called
9:56your contralateral fibers Mantra lateral
10:01fibers okay all right sweet deal now
10:04that we know that let's keep it bring
10:06let's keep bringing it to where we're
10:07going to go next so we already went from
10:08these Hemes from the visual fields we
10:11followed it down their optic nerves the
10:13optic Chasm we followed it down the
10:14optic tract we see the ipsilateral
10:16fibers and we know the contralateral
10:17fibers sweet deal what happens is from
10:20this optic tract it's going to come to a
10:23special area in the thalamus I'm
10:25actually zooming in on the specific
10:27nucleus on that Thalamus but let's say
10:28pretend here
10:29that I
10:30have I draw kind of like a little view
10:33of the thalamus it has kind of like this
10:35like piece like symbol a little bit and
10:39it kind of looks like this and what
10:41happens is it has a special nucleus
10:45coming off of it right it has a special
10:46nucleus coming off of it like this it's
10:48called the lateral geniculate nucleus
10:51what I'm doing is I'm taking the lateral
10:52geniculate nucleus and just zooming in
10:54on it okay so this right here is the
10:56thalamus
10:59but a special nucleus of the thalamus is
11:01called the lateral geniculate nucleus
11:03I'm taking the lateral geniculate
11:05nucleus and zooming in on it okay so
11:06that we're
11:07clear so this is a latog geniculate
11:09nucleus it has a total of six layers six
11:14layers so we'll layer this one
11:172
11:193 4 five six and then same thing over
11:23here one
11:262 3 4
11:29five six why am I telling you this
11:32because any Ipsy lateral fibers go to
11:36two three and five layers so ipsilateral
11:40fibers within the lateral geniculate
11:42nucleus are going to go to layers two
11:45layers three and layers five so what
11:47does that leave for the Contra lateral
11:49the Contra lateral is left with going to
11:511 four and six so then the contralateral
11:55fibers will go to 1 4 and six
12:01okay so now it comes into this area
12:03right so I'm going to kind of make these
12:04different because obviously the same
12:06color but look here from this one this
12:09is the contralateral so this one is the
12:11controlateral fiber the contralateral
12:14Fiber goes to what 1 four and six so if
12:17I were to do it let's actually just make
12:19it a different color from this point so
12:20that we're not confusing this so now I'm
12:22going to come from this contralateral
12:23fiber it's going to be maroon it's going
12:25to give connections to four it's going
12:28to give connections to six and it's
12:31going to give connections to
12:33one then the Ipsy lateral fibers are
12:37going to go to two 3 and five okay and
12:44the same thing is going to happen over
12:46here let's say that I just for the sake
12:47of it I I do the same thing over here
12:49the ipsilateral fibers and the Contra
12:51lateral fibers over here so this one
12:52right here is the Contra lateral I'm
12:54going to keep the contralateral maroon
12:56contralateral goes to what it goes to
12:57six it goes goes to four and it goes to
13:01one Ipsy lateral
13:04fibers are going to go to two three and
13:10five now from this they're going to come
13:13out of the latog geniculate nucleus so
13:15these fibers are going to be coming out
13:17of the latog geniculate nucleus so they
13:19terminate in this area some of the
13:21fibers we'll talk about when we talk
13:22about the pupilary light reflex some of
13:25these fibers can actually go from the
13:27latog geniculate nucleus
13:30and into the specific area of the
13:32midbrain they go into the midbrain and
13:34there's two structures in the midbrain
13:35that's are very important one is going
13:37to be right here called The Superior
13:39calculus it's going to give off some
13:41branches that can go there so some of
13:42the fibers can go here to the superior
13:44calculus so some of the fibers can come
13:46to the superior calculus but a really
13:49really important one is going to be just
13:51anterior to the superior calculus
13:53there's a very important nucleus here
13:54called the pretectal nucleus so a really
13:58important nucleus here called the
13:59pretectal nucleus and we'll talk about
14:02this one and how it's connected with
14:04your basically the constriction of the
14:06pupil okay so that's the pretectal
14:07nuclei we're not going to talk about
14:09that now we're going to talk about the
14:10rest of this pathway okay I just want
14:12you to realize that some of these fibers
14:14can go into the
14:16midbrain however most of the fibers are
14:19going to continue let's do this in pink
14:21now let's bring it all nice and nice and
14:22pretty all right so coming out of the
14:25lateral geniculate nucleus there's going
14:28to be two types of fiber one is going to
14:29run through the temporal lobe and come
14:32to this area of the occipital l so you
14:35see this right here all this structure
14:36that we have right here this is
14:39representing the occipital lobe so this
14:42is the occipital
14:44lobe and this would technically be on
14:46the left side and this is the occipital
14:50lobe and this would be on the right side
14:53and what's separating them is What's
14:54called the calcarine Fisher right this
14:56What's called the calcarine Fisher right
14:58here I'm not going to do that I was
14:59remember it's the calcarine fisser all
15:02right now some of the fibers from the
15:04lat geniculate nucleus move through
15:06What's called the temporal lobe so some
15:08of them move through an area of the
15:11brain called the temporal
15:13lobe to go to the occipital lobe some of
15:17the fibers actually move through the
15:21parietal lobe to come to the occipital
15:24Lo so what what's the other one right
15:26here this would be the parietal lobe
15:30and then the same thing would happen
15:32over here so if we just continuously do
15:34this because it's going to be important
15:35that we make this very very consistent
15:37here one's going to move through the
15:39temporal lobe to come to the occipital
15:41lobe and one's going to move through the
15:43parietal lobe to come to the
15:45oxital okay sweet stinking deal this is
15:50the
15:52temporal and this one right here would
15:54be the parial the reason why I'm being
15:56so picky is because these ones have
16:00different they're different types of
16:01fibers these are actually the ones that
16:02are moving through the
16:04priolo these are called The
16:08Superior
16:10retinal
16:11fibers they also call it baram's
16:16Loop so some Barum dude must have came
16:19up with it right so these Superior
16:20retinal fibers are actually also called
16:22Barum Loop and they're moving through
16:23the prial lobe these ones that are
16:26moving to the temporal lobe are the
16:27inferior retinal f fibers so these are
16:30the inferior
16:32retinal
16:33fibers and this is actually called Myers
16:37Loop so again some some dude named Myers
16:39came up with that right so again
16:43inferior retinal
16:46fibers and this is a part of Myers Loop
16:50and this is important because it talks
16:51about when we get to lesions right okay
16:55now these that are moving through the
16:56prial lob they'll come to the occipital
16:58and go to a specific area specific like
17:01part of the occipital lobe and that
17:03specific area of the occipital lobe is
17:04actually called the
17:08striate cortex and the stri cortex is
17:12basically the primary visual cortex so
17:15the striate cortex is basically the
17:19primary visual cortex this is where the
17:24perception of these visual stimuli
17:26become what we see okay so how we
17:29perceive these different types of images
17:31okay so that's an important thing to
17:32know that these fibers are coming to the
17:34stri cortex of the occipital lobe which
17:36is the primary visual cortex where the
17:37perception of these visual Sensations
17:40are actually occurring all right now
17:43that we've done that I need us to apply
17:46some visual uh like correlations if
17:48there's certain types of lesions in
17:50different fibers here okay now the only
17:52reason I'm saying that to know this is
17:54great but why do we need to know this
17:55because we need to apply it to clinical
17:57settings so let's say here that I have a
17:59couple different lesions I'm going to
18:00make it as simp simple as possible let's
18:03keep all the colors here let's do it in
18:05like this maybe we'll do it in purple
18:07here we'll represent the lesion by
18:09purple let's say there's a lesion here
18:12so that's leion number one okay then
18:16let's say that there's a lesion right
18:17here so there's a lesion right here this
18:19is lesion number
18:21two then let's say that there's actually
18:24going to be a lesion um on the outside
18:27here and outside here at the same time
18:30so let's say that this is leion number
18:34three then let's say that we have a
18:36lesion that's occurring right here leion
18:38number
18:40four and then we'll have a lesion here
18:42like leion number five leion
18:46six and then what happens if we had
18:48damaged the whole thing lesion seven and
18:51the last thing is what if we develop
18:53some type of damage to the occipital
18:54lobe and that will be lesion eight so
18:57eight total lesions is what we're going
18:58to talk about here okay here we go if
19:02the right optic nerve is damaged let's
19:03do our visual Fields here let's get our
19:05little visual Fields here keep it super
19:07super simple
19:08here here's our visual field for the
19:10right eye so we're going to have two
19:11visual Fields here one right there for
19:13the right eye one right there for the
19:14left eye and we'll separate into left
19:16visual field and right visual Fields so
19:17again this is for the left eye this is
19:19for the right eye if this right here is
19:22damaged this right here is damaged this
19:25optic nerve then I'm losing what I'm
19:28losing using the certain types of visual
19:31Sensations from the right visual field
19:33of the right eye okay so right visual
19:35field of the right eye it's gone I have
19:38no vision in this area so let's go ahead
19:40and shade that in this whole thing gone
19:44I got no vision there I developed some
19:47scotoma right there and I lose all my
19:49vision in that that visual field then
19:52any of the information all the visual
19:54Sensations that are coming from the left
19:55visual field of the right eye that's
19:57gone too all right see you see you later
20:01that's it I lose all the information
20:04from these two visual fields of the
20:07right eye what do I develop I develop
20:09monocular blindness which side right
20:12sided monocular blindness so what is
20:15this called right here
20:19monocular
20:22blindness or anopia so we can say that
20:25this is right side monocular blindness
20:27or anopia
20:33okay simple as that and this would be
20:35leion number one so Leisure number one
20:38if you damage the optic nerve you're
20:39going to have complete right side of the
20:42eye monocular blindness no vision there
20:45second one let's say that you develop a
20:49pituitary tumor and it compresses the
20:51medial part here of the optic Asma it's
20:54compressing the contralateral fibers
20:55here so let me make two visual Fields
20:57here
20:59okay so this one is going to be again
21:02this is for your left
21:04eye and this is for your right eye what
21:08is going to be affected here if I damage
21:10the contralateral fibers what does that
21:12mean okay let's follow this one over
21:13here nasal hemir Rey I'm losing the
21:16visual Sensations from the left visual
21:18field of the left eye that's gone see
21:21you later there okay let's do this in a
21:23different color here like this this is
21:26gone okay so I lose that side I lose my
21:28temp oral visual field all right the
21:30left visual field of that left eye right
21:34then what I'm also damaging these fibers
21:37and if I damage these fibers this is
21:39picking up information from the right
21:40visual field of the right eye so now
21:42this is gone so I'm losing my temporal
21:44Vision on the right eye because I'm
21:46losing my vision in both the visual
21:49Fields the temporal Fields right the
21:52temporal Fields this is called they got
21:56a heck of a name for this one they call
21:58it High
22:01temporal
22:03Hemi anopia or anop H Hemi anopsia you
22:07can even say it like that so B temporal
22:16hemianopia okay that's done what about
22:19three okay let's say that there's some
22:21type of uh you know the internal kateed
22:23arteries kind of run nearby here so
22:25there's actually internal corate
22:26arteries that run very very near near
22:28this optic Asma right here let's say
22:31that for some
22:32reason uh these guys develop like an
22:35aneurysm right and they compress these
22:37outer parts here that' be terrible you
22:40have an anism of both of them and it's
22:42actually compressing both these fibers
22:44what fibers the Ipsy lateral fibers so
22:47now let's draw your two visual Fields
22:48here this is for three okay this is your
22:51left
22:52eye this is your right eye okay if it's
22:56damaging the ipsilateral fibers you're
22:58going to lose information from the nasal
23:00field of the left eye and if you're
23:02damaging this ipsilateral fiber you're
23:04going to lose the nasal field of the
23:06right eye well if that's bitemporal this
23:08has got to be basal basal
23:11hopia huh we turn me over and tickle me
23:15Twisted look at that that's called
23:19basal
23:22Hemi anopia or anop hopas right so basal
23:27hemianopia is the third type of
23:34lesion so that' be number three so this
23:36is number three
23:38here this was number
23:41two and this was number one okay now off
23:44to number four if you lose number four
23:47let's make our visual Fields
23:49here and I'll do it like this again left
23:52eye and right eye left and right visual
23:56Fields if I damage these bad boys all
23:58this right optic tract let's follow it
24:03the right optic tract let's follow this
24:04one first okay come over here come over
24:06here come over here okay nasal hemor
24:09retin is not going to work so I'm going
24:10to lo my lose the left visual field of
24:12my left eye so left visual field of the
24:15left eye gone that's gone okay let's
24:20follow this one if we follow this one
24:22follow this one follow this one we go
24:23over to the temporal Hemy which I'm
24:25losing it from the nasal side of my
24:27right eye
24:29well that sucks and if I loose it from
24:31the nasal side of my right eye what
24:33would I call this one they got a heck of
24:35a name for this one all right it's a
24:37little T it's a tiny bit confusing but I
24:39want you guys to remember remember we
24:40said that this was the temporal and the
24:42nasal nasal temporal
24:45right we also said that we could say
24:47that this is the left visual field and
24:49the right visual field of the left eye
24:51left visual field of the right eye and
24:54right visual field of the right eye what
24:56did I lose I lose both of my left visual
24:59fields of both eyes so because of that
25:03they call it
25:05left
25:06homo
25:09nus
25:11Hemi anopia or
25:18anopsia so that is the fourth type of
25:20lesion and you would have the same thing
25:22if that happened on the uh left optic
25:24tractor except it be right homon Imus
25:26hemianopia so again this is leion number
25:28four it's called Left homon Imus hopia
25:32now let's say that we get back here we
25:35get back here now these are the these
25:37are the freckers these are the ones that
25:38can be a little bit confusing here let's
25:40say that I do number five here right so
25:42now I damage this part the actual what
25:44loop the baram's loop which are called
25:46The Superior retinal fibers before I
25:49move on let me make a mini little
25:51diagram here so that I can really really
25:52make sense of
25:54this we can split the visual Fields up
25:56like we did over there but we can
25:57actually if we really want to be very
25:59very specific let's say I make here this
26:01is
26:02my left visual field my right eye left
26:06eye sorry left eye right eye remember
26:07how we split it into a left visual field
26:09and a right visual field for both of
26:11them guess what we can split it in 2 a
26:14upper left upper right lower left lower
26:17right okay
26:20now let's say everything up above this
26:23part that I have in blue this is all the
26:26Superior part right so this is the
26:27superior part of the retina all this
26:29down below is the inferior retina we're
26:32talking about the superior retinal
26:33fibers okay now I'm looking at the eye
26:36like for my eyes like imagine here I
26:38have my eyeball like
26:40this I'm actually fixating my eye and
26:43looking straight down like this into the
26:45eyeball okay let's pretend for a second
26:49though that I look at it like this now I
26:51take this eyeball here and let's say up
26:53here I have my Superior part of the
26:55retina and then down here I have the the
26:59inferior part of the
27:00retina the Superior part of the retina
27:03is getting hit with light rays that's
27:05coming from the lower visual
27:07fields and then the inferior retina is
27:10getting hit with light rays that's
27:11coming from the superior visual field
27:14it's freaking crazy I know but I'm sorry
27:16that's how it works so now when we make
27:19this one we have to make it like
27:23this here's left eye right eye we have
27:27to split it like this but then into
27:28fours okay Superior quadrant inferior
27:32quadrant
27:34okay okay now let's let's think about
27:37this if this Su we damage this right
27:41side the right Superior retinal fibers
27:44if the right Superior retinal fibers are
27:46damaged remember anything from the right
27:49side is coming from the left eye or the
27:52left visual field so again anything
27:55that's coming from this is coming from
27:56the left visual Fields anything that's
27:58on the right ey is coming from the left
27:59visual Fields just want to make sure
28:01that we get that completely clear if
28:04this is damaged the super retinal fibers
28:06then I'm losing the vision within the
28:09inferior visual field on the left side
28:13okay so we already know that I'm losing
28:15the actual left visual field that's
28:18already clear because anything from the
28:19right eye is picking up information from
28:21the left visual Fields so all of this is
28:24gone the left side but remember super
28:28retinal fibers only pick up the
28:30information from the inferior visual
28:32field so really we're only losing this
28:35part
28:36here and we're only losing this
28:39part here so because I'm losing vision
28:44within the lower quadrant of the left
28:47visual field we call this what this
28:50one's a heck of a one two left
28:55inferior quadrant
29:00Hemi
29:08anopia okay so left inferior quadrant
29:11hemianopia and it's because we're losing
29:13our vision within the left visual
29:16field and in the inferior plane Okay
29:21then if we did a lesion here on the
29:22sixth one right so we said that we
29:24damaged the sixth one here so let's
29:26actually do this one up here cuz we
29:28running out of room up there so let's do
29:29the 6 one up here so the 61 we're going
29:32to damage right
29:34here okay so let's make our visual
29:37Fields same thing we got to make this
29:39into four parts we got to cut it up like
29:42this cut it up like
29:44this inferior retinal fibers and this is
29:47from this is actually on the left side
29:48so this is the left inferior retinal
29:50fibers so that means that it's receiving
29:52information from the right visual Fields
29:54okay so we already know it's right
29:55visual fields that are being affected
29:56done okay and again this is this is left
29:58eyee and this is right eye we know that
30:00the right visual fields are going to be
30:02affected but we know it's the inferior
30:04part of the retina that's being affected
30:06if the inferior part of the retina is
30:07being affected we're losing vision in
30:09the superior plane so now what's going
30:11to happen we're losing the right visual
30:13Fields but not in the inferior the
30:15superior plane so now you're losing this
30:19part here what is this one called This
30:20is called
30:24right Superior quadrant
30:29Hemi
30:36anopia okay that's that one so right
30:39Superior quadrant hemianopia and if you
30:41get this one then you should be able to
30:42get the same thing if I damaged this
30:45other side okay it would just be the
30:47exact opposite then then be left
30:48Superior quadrant hopia if I damaged
30:51this uh Superior retinal fibers of this
30:53side on the left side then I'd have
30:55right inferior quadrant hopia it's the
30:58same thing okay holy sweet goodness now
31:02we have this seventh one here seventh
31:05one is I damage this whole thing you
31:07know I never even told you what the heck
31:08these pink structures are I am so sorry
31:11about that these pink structures
31:14here all of these this one here this one
31:17here from both sides they're called
31:20optic
31:22radiations they're called optic
31:24radiations so these Superior retinal
31:26fibers and infer retinal fibers or make
31:28up what's called the optic radiations or
31:29you can call this the
31:31genico
31:34calcarine tract and the reason why it's
31:36coming from the geniculate body to the
31:38calcarine fissure okay so these optic
31:41radiations let's say that I damage the
31:44right optic radiation so I damage my
31:48right
31:50optic
31:52radiations okay write optic radiations
31:55freaking
31:56going okay so if that's damage let me
31:58get rid of this right here so I can make
31:59room here same thing let me right draw
32:02this right here this right here but
32:04because it's not affecting it's a losing
32:05you're losing both the quadrants so
32:06we're just going to make it two little
32:07boxes
32:08here if I damage this one and I damage
32:11this one what do I remember anything
32:13that's on the right side I'm losing it
32:15from the left visual Fields so if I'm
32:18losing it from the left visual Fields
32:20then what must be happening here I'm
32:21losing it from both the superior and
32:22inferior planes so that means I'm losing
32:25all of the information from the left
32:28visual field of the left eye and the
32:32left visual field of the right eye what
32:36do we call this one if you remember
32:38doesn't this seem very very familiar it
32:40looks just like this one right over here
32:43what is this one over here called this
32:45one was called Left homon Imus hopia
32:48it's the exact type exact same type here
32:50so what is this called
32:53Left homon
32:56Imus h
32:59am
33:05anopia okay last one and we're
33:08thankfully done here let's say that you
33:10damage a specific part of the oxipor
33:11cortex you know there's two arteries
33:13that are supplying the occipital lobe
33:15here there's What's called the posterior
33:16cerebral artery which is a part of The
33:18Circle of
33:20Willis and there's another one here
33:22called the middle cerebral artery which
33:24is actually a branch of the Circle of
33:27Willis let's say that you develop some
33:29type of most common cause here of some
33:30type of lesion within the oipal lobe is
33:33you develop a lesion here within the
33:35posterior cerebral artery you still have
33:38blood that can supply the occipital LOE
33:40from the middle cerebral artery so this
33:42is the middle cerebral artery you still
33:44can get blood to the occipital lobe now
33:46there's a specific area in the occipital
33:48lobe that picks up very very um acute
33:51Vision that is within the macula of the
33:53eye okay so there's the macular region
33:58of the occipital ope if the posterior
34:01cerebral artery is uded you might affect
34:03the blood flow to the macular region of
34:05the occipital but because we have these
34:07middle cerebral arteries they're still
34:09going to get blood to the macula so what
34:11happens here is something really
34:13freaking weird is because you
34:17spared the macula by giving it blood
34:21flow from the middle cerebral artery you
34:23spared the macular region of the
34:24occipital Lo then whenever you do their
34:26visual feel so again here's the left
34:29here's the right
34:30eye split up their visual Fields here
34:33into left and right there's something
34:36really thing weird here that we can
34:38actually include into this I can put a
34:39circle here and this circle here is
34:42representing the center of that part in
34:45the eye you know how we have the macula
34:47ludia where the fobus andalus is the
34:49highest concentration of cones what
34:51happens is if you can actually spare
34:53that macula because the poster cerebral
34:55artery is occluded but the middle
34:57cerebral artery still getting blood flow
34:58to this area this area of the macula is
35:01uh the this area of the occipital lobe
35:03where the macular impulses are coming to
35:05that will be spared but again everything
35:07is on this right side so if the right
35:09part of the occipital lobe is damaged
35:11anything from the left visual field will
35:12be lost so what am I going to
35:15lose I'll lose this part of the left
35:17visual
35:18field and I'll lose this part of the
35:20left visual field but guess what I will
35:22not lose I won't lose this specific area
35:25right there which is actually called the
35:27macular region so this is called it
35:29looks like it's oh isn't this left homon
35:31nimus hopia yeah this right here is
35:34called
35:36Left
35:38homo
35:40nimus
35:44hemianopia but with sparing of the
35:48macula with
35:51sparing of macula
36:01okay that's the whole purpose of
36:04this all right so in this video we
36:07talked about the visual field processing
36:09we talked about the visual field
36:10processing we talked about the actual
36:13visual pathway and we talked about
36:15Associated lesions that could develop
36:17within the different parts of this
36:19visual pathway guys I really hope all of
36:21this made sense I really really really
36:23do hope that you guys did enjoy it and I
36:25hope it helped if it did please hit the
36:27like button comment down in the comment
36:28section and please subscribe all right
36:30Engineers as always until next time