Diabetic Retinopathy: Signs and Diagnosis

by Richard Mitchell, MD, PhD

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    00:00 It's a spectrum of disease. So again, we talked about, you know, 90% of people with poorly controlled type 1 diabetes, only a quarter patients with type 2 diabetes developing disease.

    00:13 Pretty much everyone with diabetes will have some of these manifestations especially the longer that the diabetes goes on. So we will see a spectrum of disease from full-blown blindness to just some of these subtle changes that we'll see on fundoscopic exam. So early disease is very much asymptomatic. There won't be any visual changes, we won't really notice it, but if you look through the pupil and do a fundoscopic exam you will be able to see some of the changes we'll see in a minute. When patients begin having symptomatology, this is due to hypoxia. So this is inadequate perfusion of the rods and cones. And you will begin to see flashes, the poor little rods are saying "wait, not enough oxygen, wait, not enough nutrition" and they fire inappropriately. They reached threshold fire and you get these little flashes of light. So, that's one. Depending on little micro areas of scarring, you may see subtle changes in vision such as indicated here little floaters. There will be diminished visual acuity. This is because of edema and/or hemorrhage within the vitreous and/or the macula so that you're getting a little bit of distortion at your central focus of best visual acuity. So things will look a little bit fussy. There may be sudden painless, usually monocular so it's just one side, loss of vision and this is going to be retinal detachment. This is an ophthalmologic emergency. You need to get that retina re-attached as soon as possible to ensure that you have adequate preservation of all those nerves, connections, rods and cones, etc. Now this is not part of the retina, this is clearly up here in the lens more anterior, but diabetes also makes patients prone to early cataract formation. That same hyperglycemia chronically leads to nonenzymatic glycation of the proteins in the lens and you'll get premature clouding. Okay, again, not related to the retinal process but something that you should be aware of in diabetic eye disease. Alright, let's look at the fundoscopic exam. What do you expect to see? So, on the left hand side that's come up is our normal fundoscopic exam. Over on the left hand side, we have our optic disc, that's where the optic nerve is going out leaving the eye. And you have retinal veins or retinal arteries. We've looked at this in a previous session. And there's a little bit of pallor in that area because there is a lower density of small vasculature as the nerve structures are there. Kind of midpoint all the way over in the middle is our macula, which is going to be our best area of visual acuity and then that pit that is the fovea where we have the highest density of cones.

    03:10 Okay, that's what we expect to see and we do expect to see some branches of vessels, but not a lot of other things that are in there. Here's diabetic retinopathy. It's a higher magnification than the one on the left. The eye isn't bigger. These are the changes that we've been talking about. So the hard exudate at the top. That is material that's come out protein and lipid from leaky vessels. Hemorrhage. So, newly formed vessels or vessels that are damaged because of the diabetes will leak and have hemorrhage. We have microaneurysms indicated there. That again because the pericytes are very susceptible to irreversible diabetic damage and loss. And now we have dilation of the small capillaries.

    04:04 Cotton wool spots are because of focal areas of ischemia and infarction. So those are the changes, that's a pretty ugly looking retina overall. We can still see on the right hand side our optic disc with vessels coming in and out. In the macula is there, that kind of darker area under the microaneurysm label. It's also there but it looks a little bit fussy, it's not as well defined. There may be some macular edema. Okay, the other changes that happen in proliferative diabetic retinopathy are the much more prominent aneurysms, much more prominent neovascularization again driven by the vascular endothelial growth factor. And because we have many many more immature blood vessels that haven't yet completely made nice circular vascular flow, we're going to get hemorrhage. So, kind of accentuation of some of the things we saw in the nonproliferative version of the diabetic retinopathy.

    About the Lecture

    The lecture Diabetic Retinopathy: Signs and Diagnosis by Richard Mitchell, MD, PhD is from the course Posterior Segment Eye Diseases.

    Included Quiz Questions

    1. Hypoxia
    2. Hyperemia
    3. Hypercapnia
    4. Neovascularization
    5. Microaneurysms
    1. Floaters
    2. Flashes
    3. Macular degeneration
    4. Hard exudates
    5. Cotton wool spots
    1. Monocular loss of vision
    2. Presence of flashes and floaters
    3. Appearance of cataract
    4. Macular edema
    5. Rod dysfunction
    1. Focal ischemia and infarction
    2. Focal hypoxia and necrosis
    3. Focal irreversible microaneurysm
    4. Focal areas of inflammation
    5. Focal areas of neovascularization

    Author of lecture Diabetic Retinopathy: Signs and Diagnosis

     Richard Mitchell, MD, PhD

    Richard Mitchell, MD, PhD

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