Previously, we've talked about other
inflammatory processes that involve
other structures of the external eye.
We've talked about blepharitis,
we've talked about hordeolums.
Today we're going to go one layer
deeper and look at the conjunctiva.
We're going to look at inflammation of that, or
conjunctivitis, more colloquially known as "pink eye".
As always, I want to acknowledge the help and
the assistance in the great job that was done on this
slide presentation of Dr. José Mata.
Let's talk about inflammation of the conjunctiva.
It overlies the sclera, and it's going to be
that vasculature, that vascularized membrane
that provides additional
lubrication to the front of the eye.
Usually the vessels are not apparent
and we normally have nice wide eyes,
but when that gets inflamed,
we'll have conjunctivitis
And we'll continue that into our next session.
The conjunctiva has two components.
There is the bulbar conjunctiva that's
associated with the eye orbit, with the eye itself
and the palpebral conjunctiva
that's on the inside of the eyelid.
And both of those can become inflamed.
And typically, when we do have
conjunctivitis, both are involved.
So conjunctivitis or pink eye is
inflammation of the conjunctiva.
Remember, conjunctiva is this highly
vascularized membrane that sits over
kind of the whites of the eye, over the sclera.
And this is going to be an important,
highly vascularized membrane
that will allow more fluid production
or allow the transudation of fluid to help
kind of keep the external part of the eye
well liquefied, not liquefied, but well lubricated.
And you can have inflammation of this as
you can have inflammation of almost anything.
And it can involve either the bulbar
conjunctiva, which is what we see there
over the whites of the eye
or over the orbit of the eye,
or it can involve the conjunctiva that sits on the
inside of the eyelid or the palpebral conjunctiva.
Either one will work and
frequently everything is involved.
Two kind of major flavors in
terms of the cause of conjunctivitis.
So we can have a noninfectious conjunctivitis
which will be non-allergic or allergic.
And clearly, if you have a noninfectious
conjunctivitis, we must have an infectious one
and that will be either bacterial or viral.
Okay, let's get into a little bit more detail.
Of the infectious causes, viruses
are going to be quite common.
And of the viruses, adenovirus is going to
be the vast majority of the causal organism.
These are quite diffusely out there in the environment.
And so 65%-90% of the conjunctivitis that's
associated with virus is going to be an adenovirus.
And we're just seeing a couple eyes that
are showing you the characteristic inflammation
of the conjunctiva, again, inflammation of conjunctiva
is no different than inflammation anywhere else.
This is vasodilation and increased vascular permeability
with the recruitment of inflammatory cells.
It just seems to be happening here in the
conjunctiva of the eye.
Okay, so that's most common cause.
The second one is herpes simplex virus, it's
going to be more common in the pediatric population.
And then in the geriatric population, varicella
zoster is going to be the most common virus.
So depending on the face in front of you, whether
it's kind of a very young face, a very old face or
the rest of the world, you can make an educated
guess about which virus is likely to be causing this.
Because it's a viral infection, we
are not bringing in many neutrophils.
It's going to be predominantly
kept in check or eventually eliminated
by actions of T-cells and some macrophages.
So it's going to be overall a sparse mucus discharge.
There will be inflammation that
also extends up into the lacrimal gland
in the lateral part of the eyes, as
well as involving the lacrimal caruncle
at the medial canthus.
In both of those cases, because of
inflammation of that part of the apparatus,
there will be increased lacrimation,
there will be a tendency to have tearing.
Important part about viral etiologies for
conjunctivitis is that they are mostly self-resolving.
We try to prevent a secondary
bacterial infection but usually,
given enough time and an intact immune
system, we can eventually make them go away.
Bacteria, on the other hand,
are going to need a little bit of help.
So the most common bacterial
cause of conjunctivitis is Staph aureus,
very common skin pathogen, and it's also
going to be very common around the orbit of the eye.
And if it gets into the conjunctiva, it can
wreak a significant amount of damage.
In kids, the most common is
probably Haemophilus influenzae.
In the newborn population, it's Neisseria,
and we actually even administer eyedrops
in many neonatal situations to
prevent the spread or the bacterial
expression of the Neisseria in the eye.
In developing countries,
it'll be Chlamydia trachomatis
So, again, kind of depending
on who's staring back at you and,
and or whether you're in a developing
country or in an industrialized country,
you can make an educated
guess about the infectious agent.
You're going to know that it's bacteria
because of the presence of pus.
so because now this is a bacterial
infection, we are recruiting neutrophils.
And neutrophils are going to have a
characteristic yellow kind of color,
and there will be much more of an exudate.
We're going to need to...
When we recognize that pus, we're
going to need to treat with antibiotics because
that sort of bacterial infection is
unlikely to spontaneously resolve.
Those are the infectious causes.
On the other side of the equation
are the non-infectious causes,
and you can have allergic or non-allergic.
Of the non-allergic, these are autoimmune diseases.
Dry eye syndrome or sicca syndrome
and Sjogren syndrome involve inflammation,
autoimmune-derived or driven
inflammation of either the conjunctiva proper
or of the lacrimal system.
And so we can have
an immune-based response that
isn't driven by extrinsic allergens.
On the other hand, allergic
conjunctivitis is due to airborne allergens.
and because we're getting mast cell
degranulation, and a variety of other things,
that's how we're getting the inflammation.
And obviously it's going to be bilateral.