If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Main content
Current time:0:00Total duration:13:21

Video transcript

did you know that diabetes is the most common cause of blindness and individuals from the ages of 25 to 65 and blindness can be caused by multiple different complications associated with diabetes including glaucoma and cataracts however in this tutorial let's discuss the most common cause of blindness due to diabetes which is a condition known as diabetic retinopathy and if we break down the term we can receive generally and understanding of what this disease is so you have retina here meaning the retina and pathy meaning disease so diabetic retinopathy is a disease of the retina that's caused by diabetes and to describe what the retina is let's bring in a diagram of the eye and go through some of the structures as it will help us as we learn more about this condition over here on the Left we have a cross-section of the eye and there's a few important structures to note so this is the front of the eye here and this is the back of the eye and this part right here is known as the cornea and it is where light initially passes through as it goes through the eye and then it hits this structure right here which is known as the lens and the lens focuses the light on this structure in the back of the eye it's kind of brownish structure and this is the retina and then exiting the back of the eye here this is the optic nerve then you can also see all of these blood vessels that are traveling through the retina and then exit the back of the eye in the middle of the optic nerve so if you look over here on the right this is a front view of the eye so this is kind of what it looks like when a doctor looks into your eye so here right here we have what's called the optic disc and the optic disc is really just the convergence of the retina and where it exits thighs so this is really actually the optic nerve exiting the back of the eye and then over here you have a structure called the fovea and the fovea is the portion of the retina with the highest density of cones which are the nervous receptors that correspond with color and more high-resolution so this is the portion of the retina that produces the highest resolution image so in a sense you can kind of think of the fovea as producing an HD or a high-definition quality image whereas kind of the more periphery of the retina on the outside will produce a much lower quality image now that we have a very basic general orientation to the eye and the retina let's use this drawing to discuss the three stages of diabetic retinopathy and they are diabetes without retinopathy non or pre proliferative diabetic retinopathy and proliferative diabetic retinopathy and one thing that's important to note is that these stages of diabetic retinopathy are defined by their pathology not by the clinical presentation or their symptoms but before we dive into the pathology here what are some of the common symptoms of diabetic retinopathy well since it's a disease of the retina caused by diabetes it makes sense that the symptoms are typically visual and most of the symptoms tend to be fairly mild initially they are things like blurry vision or seeing dark spots or floaters however sometimes the symptoms can be very serious such as sudden onset of blindness all right so now let's get back to these stages of diabetic retinopathy so the first stage I mentioned is diabetes without retinopathy so why do we consider diabetes without retinopathy a stage of diabetic retinopathy it doesn't quite make sense and this is because the stages are dictated by the underlying pathology and so long before someone with diabetes develops visions it changes the underlying hyperglycemia or high blood sugar levels in their blood causes damage to cells known as parasites within the retina so these retinal parasites are specialized contractile cells that surround the retinal vasculature here and they're very important for helping regulate blood flow throughout the retina and the damage to these parasites is believed to be caused by an inability to properly metabolize the glucose within these cells and then this results in osmotic damage now this damage to the retinal pericytes is the earliest stage of diabetic retinopathy and it's likely present in many if not most individuals with type II diabetes for at least a few years however unfortunately this damage is only detectable under a microscope and therefore the retina on ophthalmologic or on an aisle eye exam looks normal it looks something like this so therefore early in the course of diabetes individuals will not necessarily have visual disturbances or signs of disease on exam however this does not necessarily mean that the damage is not occurring it's just not detectable and the next stage of diabetic retinopathy is that of the non or pre proliferative diabetic retinopathy so recall that I just mentioned that these retinal pericytes help regulate blood flow through the vessels throughout the retina and when they're damaged this results in a weakening of the capillary walls as well as increased blood flow what happens when these capillaries are damaged allows for the formation of micro aneurysms which are focal dilations of weakened vessel walls and since these aneurysms occur in the micro vasculature of the retina the vessels themselves are very small and not visible on optoma logic exam however the micro and aneurysms are and so they kind of look like these red dots that just appear kind of randomly throughout the retina and if we bring in an actual picture here of the retina you can see that this is actually what they look like under examination so they're a little bit hard to see but they're these dots right here right here and here which are typically the first clinical sign of diabetic retinopathy however this isn't the only clinical finding for this non or pre proliferative diabetic retinopathy stage in addition to damaging the retinal capillaries this loss or damage to the retinal pericytes also results in increased vascular permeability and basically what this means is that the capillaries become leaky now this leakiness allows for large molecules such as proteins and lipids that are normally retained within the vessels to leak out into this retinal issue and unfortunately there isn't a normal mechanism to allow these to be reabsorbed so as you can imagine if proteins and lipids were to leak out they get trapped and this also can be seen under a dilated eye exam and it kind of appears as these yellow white flecks on the retina as you can see here and this finding is known as a hard exudate and once again even though this is just a drawing of the retina it's actually fairly representative of what actual hard exudates look like so you can see once again all of these micro hemorrhages or the micro aneurysms and the retina and then these white yellow flecks all over and that's the proteins and lipids that have leaked out to form these hard exudates and the retina so these two clinical findings are very characteristic of this second stage or the non or pre proliferative stage of diabetic retinopathy and because diabetic retinopathy is categorized by the pathologic findings and not necessarily the clinical presentation this stage of diabetic retinopathy may or may not be symptomatic so it usually begins about 15 to 25 years after someone's initially diagnosed with diabetes and it can last for many years before it progresses to the next stage which is proliferative diabetic retinopathy now proliferative diabetic retinopathy can be asymptomatic however it's pretty uncommon so most individuals that reach this stage of diabetic retinopathy usually will have at least blurry vision or the presence of floaters and as its name suggests proliferative diabetic retinopathy is characterized by vascular proliferation within the retina and the reason for this is that all of the micro vascular damage that occurs in these first two stages of diabetic retinopathy results in something called ischemia and what ischemia is is a lack of oxygen supply to the cells of the retina so what the retina will do is it tries to compensate for this ischemia by producing a growth factor known as veg F which stands for vascular endothelial growth factor and veg F does exactly what its name suggests it produces new blood vessels however these blood vessels in diabetic retinopathy are abnormal and the retina is not able to compensate for the ischemia so it looks something like this over time so you can see there's all of these new blood vessels that have formed within the retina and similar to the micro aneurysms and the hard exudates this vascular proliferation can also be identified on a dilated eye exam and it looks something like this so you can see some may be a little bit more normal larger vessels in the retina but then throughout here are these a little bit lighter kind of squiggly looking newer vessels so this is that vascular proliferation that is indicative of the proliferative diabetic retinopathy and unfortunately once diabetic retinopathy hits this third stage and becomes proliferative the clinical course is pretty unpredictable and it can actually be fairly severe resulting in potentially vision threatening complications such as vitreous hemorrhage or retinal detachment so now that we have a better understanding of the pathological mechanisms of diabetic retinopathy how can we use this information to learn how the condition is treated well first off the treatments are aimed at halting the underlying pathologic mechanisms of diabetic retinopathy however their use is more commonly dictated by the severity of symptoms so we'll start with their first stage the diabetes without retinopathy and since the pathologic mechanism of diabetic retinopathy is directly related to the underlying hyperglycemia associated with diabetes the best way to prevent or delay the progression of diabetic retinopathy is early an aggressive control of one's blood sugar with lifestyle modifications in anti-diabetic medications however oftentimes this is not enough and over time even individuals with very well controlled diabetes may develop diabetic retinopathy so because these early stages are often a symptom at like it's also important for all individuals with diabetes to have a yearly dilated eye exam performed by an ophthalmologist to look for the signs of diabetic retinopathy now once an individual has signs of diabetic retinopathy such as the micro hemorrhages or the micro aneurysms and these hard exudates and they move into that second stage of diabetic retinopathy and now the treatment is dependent on symptoms so if that individual is say asymptomatic their only treatment is still to just maintain proper blood glucose regulation and the yearly eye exam however as soon as symptoms such as blurry vision or floaters develop then an individual with diabetic retinopathy should be placed on anti veg F medications and these medications will prevent the proliferation of new blood vessels in the retina and therefore help prevent the progression to proliferative diabetic retinopathy now unfortunately once someone has evidence of proliferative diabetic retinopathy with this vascular proliferation of the retina the clinical course is actually pretty difficult to predict so for this reason anyone within this stage of diabetic retinopathy is recommended to undergo a procedure known as laser photocoagulation and this is a process by which very precisely focused lasers are used to stop the growth of these vessels on the retina and unfortunately this treatment is not necessarily curative it's more aimed at preventing serious complications of diabetic retinopathy such as retinal detachment where as its name suggests the retina can become detached from the posterior wall of the of the eye or vitreous hemorrhage where these new blood vessels actually burst and bleed into the inside of the eye and both of these conditions may potentially result in permanent blindness therefore anyone with diabetes who develops sudden onset vision loss should be evaluated emergently to rule out these complications so diabetic retinopathy is a disease of the retina that's caused by diabetes and it tends to be a slow progressive complication of diabetes that eventually affects nearly all individuals with diabetes mellitus however the underlying mechanism diabetic retinopathy is directly associated with glycemic control or blood glucose regulation therefore like many of the complications of diabetes proper treatment of the underlying condition can prevent or at least slow the progression of diabetic retinopathy