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
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