Retinal Disorders: Introduction

by Carlo Raj, MD

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    00:01 Our next issue will be in the retina.

    00:04 I want you to picture the retina, the different layers that we have.

    00:07 We talked about how these refractoriness, which is then provided by the lens, and which it will then converge, so that it can have proper interpretation by the retina, so that it can then feed into your optic nerve, correct? Take a look.

    00:22 Now, the picture on the left, is a low amplified version of your retina, or the components of the posterior segment.

    00:31 Now, what you want to do here, and I just want to make sure we're clear about terminology, keep the segment from anterior-posterior separate from chamber anterior-posterior.

    00:42 The segment and anterior-posterior is divided by the lens.

    00:46 So anything behind the lens is the posterior segment.

    00:50 Whereas when we talk about the anterior-posterior chamber, it is the iris that is then going to then divide the anterior-posterior chamber which then becomes important for as in glaucoma.

    01:02 In the posterior segment of the vitreous body.

    01:05 And then further deep we have the layers of the retina as you see here.

    01:09 It is quite important that you know the different layers, our focus however will be moving further towards your, take a look at the bottom of the left figure here, and you notice that we are in our photoreceptor layer.

    01:24 The photoreceptors, I want you to know, transition from the left over to the image on the right, because what you are seeing here as far as the image on the right, is the entire retinal layer and specifically I need you to focus on the photoreceptors with the rods and cones.

    01:40 Do you see that? Have you identified them? The C as in cones used that for color, responsible for color orientation.

    01:47 Whereas the rod would be responsible for black and white.

    01:50 Next, underneath that photoreceptor layer, we have an important layer called the pigment layer.

    01:58 That becomes important later to us because as we then go on to talk about macular degeneration.

    02:04 We'll talk about substances that made them accumulate between the retina pigmental epithelium known as drusen, okay? So spend a little bit of time to make sure that you focus on what I have given you here, pathologically.

    02:18 And next, we'll go into retinal disorders.

    02:21 I need you to focus on and spend a moment on normal fundoscopic examination.

    02:29 What you see there smack dab in the middle.

    02:32 That is a little bit dark, perfectly normal on fundoscopic examination.

    02:37 There you are, medical student, resident, what have you.

    02:40 And you're looking into the eye of your patient, and you're noticing the retina, right? You know, what you see there in the middle that's dark, no doubt represents the fovea.

    02:50 What is the fovea? The fovea is that part of the eye or retina that has the most concentrated number of cones.

    02:58 In other words, has incredible, incredible visual acuity.

    03:02 Now, where are the foveas located around it would be then called what, please? Macula. Okay? So the fovea would be the highest concentration of cones, a lot of photoreceptors thus it gives you that dark appearance.

    03:17 Around the fovea, it is in the region of the retina, that we then called macula.

    03:22 Is it understood? Later on, our discussion will go into macular degeneration, and unfortunately, the number one cause of blindness in the US, is due to macular degeneration as we shall see.

    03:35 That it's important that you know what normal looks like first.

    03:37 Next, while we said that, in the photoreceptor layer, that ones the light and the image in front of us has been properly interpreted, that all these images are then properly interpreted by the retina.

    03:51 And eventually all these has to be signaled into where? The optic nerve.

    03:55 And what you're seeing here over to the right a little bit would then have to be the optic disc.

    03:59 Now, in that optic disc, there are a couple of structures that you want to make sure that you know are either coming in or out.

    04:06 The structure obviously going into the optic disc so that you can go then to the occiput for proper interpretation of your vision, would have to be the? Good! Optic nerve, right? The optic nerve.

    04:20 Now, we're not gonna go into neuroscience in this discussion, and make sure that you do know the proper anatomical pathway of the optic nerve, including optic chiasms and so forth.

    04:31 Now, the structure or the blood vessel coming out of the optic disc would then have to be the central retinal artery and that which is then draining into would then be your central retinal vein.

    04:42 All that is then coming in and out of your optic disc.

    04:46 The middle there of the optic disc, we then have something called the cup.

    04:50 A cup.

    04:51 So the physiologic cup, is the actual, actual aperture in which we have all these structures that are moving in or out.

    04:58 I need you to focus how small the cup is.

    05:02 Why? At some point in time what may then happen is increase intraocular pressure.

    05:07 And when you have increase intraocular pressure, you may then cause, ?pathologically cupping,? in which a cup then becomes bigger.

    05:18 And also you see where we have the optic disc on the right.

    05:23 What if that optic disc becomes really bright-like in examination? Well, we then call that papilledema.

    05:32 If you were to notice papilledema, then what does that mean to you? Oh my goodness, there might be increased not just intraocular pressure, but increase cerebral pressure. And keep that in mind.

    05:42 All these are important for us in normal funduscopic examination.

    05:45 A couple of other things that I'll point out to you, as we proceed, including the retinal artery and the retinal vein.

    05:52 The darkest structure going into your optic disc, would be the retinal vein, and that which is then coming out would then be the retinal artery.

    06:01 You want to keep that separate from the central retinal artery and vein, as we should go.

    06:07 So I've given you a lot of information here.

    06:08 But do not worry, everything that I've discussed here physiologically, well then obviously be applied pathologically.

    About the Lecture

    The lecture Retinal Disorders: Introduction by Carlo Raj, MD is from the course Retinal Disorders.

    Included Quiz Questions

    1. Lens
    2. Iris
    3. Pupil
    4. Vitreous
    5. Uveal tract
    1. Drusen
    2. Cotton-wool spots
    3. Hollenhorst plaque
    4. Roth spots
    5. Exudates
    1. Fovea
    2. Macula
    3. Optic disc
    4. Optic cup
    5. Parafovea
    1. Papilledema
    2. Cotton-wool spots
    3. Arteriovenous nicking
    4. Optic disc pallor

    Author of lecture Retinal Disorders: Introduction

     Carlo Raj, MD

    Carlo Raj, MD

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    A well structured lecture
    By Reet S. on 08. August 2021 for Retinal Disorders: Introduction

    This lecture is indeed helpful as an intro to the retina. Thank you, Doc.