RETINA

 The retina 

The retina which is the deepest layer of the eye remember that we have a fibrous tunic which consists of the sclera and cornea then we have the vascular tunic which contains the choroid and then the neural tunic which has a lot of neurons as you can see and that really is just the retina and we'll go to this image real quick just for a minute but when light enters your eye it's gonna go through the pupil obviously and it's gonna go through to the back of the eye and here's the retina and so in doing so in following that path the light's gonna have to pass through the cornea the anterior chamber the posterior chamber the lens and then through the vitreous chamber and then finally that light is gonna strike the retina at the back of the eye in which you can see a little bit more macroscopically in this picture right here and within the retina we have three cell types the first type is called the photoreceptor cells or just photoreceptors and these are the cells that initially detect the light and there are two subtypes of photoreceptor cells and those are rods and cones we're gonna have a separate video where we go over the major differences between these but I'll just say this for now rods detect non colored light so non color vision just bright and dark and cones detect color okay see four cones see four color then we also have bipolar cells and then we have ganglion cells which eventually become continuous with the optic nerve these are the three major cell types there's also a couple other cell types called amacrine cells and horizontal cells and we're not going to get into these very much most Anatomy courses don't but they just exist pretty much to find tune and regulate the functions of these cell types particularly bipolar cells and ganglion cells okay now before we go any further I want you to notice something so we've got light that we mentioned was passing through the eye okay like this in this direction and then it strikes the retina but what's interesting about the setup of this is it actually doesn't encounter the photoreceptors first actually if we follow the passage of light the photoreceptors are at the back of the eye they're there actually we could say superficial to the ganglion cells so actually the light has to travel through the ganglion cells and then through the

bipolar cell layer and then finally is

able to make contact with the

photoreceptors but it's the

photoreceptors that initially detect

that light and then the photoreceptors

will have an effect on the bipolar cells

which will then in turn have effects on

the ganglion cells and we're gonna look

at that now in this slide okay now to

really understand what happens here we

have to understand what's happening in

the dark so imagine a situation where it

is complete darkness okay

so let's first of all say it's night

it's dark out you're in your room

there's no night lights doors are closed

and you have blackout curtains so you

can't see anything all right so I have

the photoreceptor cells in blue now

interestingly in the dark the

photoreceptor cells are actually

depolarized okay so the photoreceptor

cells are actually D polarized and that

not may not now that probably doesn't

make a lot of sense because usually only

think of depolarization we think of

activating but trust me this is how it

is and it will make sense in the end so

in the dark photoreceptor cells rods and

cones are depolarized that being said

that means the photoreceptors are

activated and they activate the next

neuron in sequence which is called a

bipolar cell it's also worth mentioning

that the way that photoreceptors

activate the bipol

Vitreous Humor

 Today I'm going to talk about vitreous

opacities and vitreous floaters so I

wanted to express some gratitude for a

couple people one is Lilian in our

office who has helped us extensively

with our presentations and I'm really

grateful to her for that and this is a

picture of her here and also I'd like to

express gratitude to Geri seabag who is

a virtual retinal surgeon in California

who has been a pioneer in vitreous

opacities and floaters  and not only

is he a a very erudite and sophisticated

person but he is he has been

consistently and politely pushing this

field forward for many decades

particularly given the attitude that

many of us have towards patients with

floaters and dismissing their symptoms

and he's been very gently and

persistently moving the field in the

right direction so first we'll start

with vitreous Anatomy and over here on

on the Left panel you can see a autopsy

eye in which the choroid the sclera was

removed and the choroid was detected

anteriorly and then the vitreous base

was the second off of the retina and you

could see that early in life the

vitreous gel is firm it's very clear and

and it's it has a structure.

It doesn't

just collapse when you set it on a on a

surgical cloth and if we look at the

iron cross section we can see that the

the vitreous emanates from the aura

sirata and it's always connected to this

space during life there's a little space

right here and then the vitreous is

connected to the lens and this space

here behind the lens that posterior

capsule is called Berger space or the

retro mental space of galette

there are fibers that extend up to the

pars plana and even the pars Picatta and

these aren't shown on this diagram but

we know that those exists because when

we're opera

patients with proliferative retinal

diseases we can see contraction with the

retina actually gets pulled from here up

onto the ciliary body and by coming

across with a cutter in shaving those

vitreous bands we can release that

traction

there's cloak haze canal which emanates

from the disk and if we blow the space

up here we can see this this area a

little better there's this little space

here a little space behind the capsule

and then this type adhesion between the

anterior vitreous face and the posterior

capsule and this is why cataract

surgeons get vitreous loss when they

break the posterior capsule it isn't

because they're you know going crazy

back here it's it's because whenever the

capsule is torn it often actually

breaches the vitreous phase right here

if we look during development at a

neonatal or our embryonic eye we see the

the lens with the embryonic nucleus and

the fetal nucleus and then we see the

tunic of a skull osa lentes which is

contiguous with cloakers canal and this

branch of vessels and this regress is

overtime and forms a a little tuft in

adults this is a a embryonic or neonatal

lens and when we do retinopathy

prematurity exams which I don't do

anymore but I did when I ran the

neonatal intensive care unit service at

Parkland Memorial Hospital in Dallas we

can see these these lenses these blood

vessels on the lense in fact when we're

doing laser for retinopathy prematurity

we try to avoid the bigger lenses into

order to avoid causing a sub capsular

cataract and here is an example of a

incompletely regressed Bergmeister is

patella the remnant of the Clos case

canal and this is a picture from dr.

Henry Kaplan who is a famous

ophthalmologist in Louisville

specializes specialists and many things

including you be honest so here are some

some work where we're comparing an

embryonic vitreous

to a middle-aged vitreous to an aged

vitreous and one of the problems we have

with examination of the vitreous is that

the optics aren't ideal we're unable to

get the slit arm far enough over to

examine the posterior vitreous

effectively because of the optics of the

pupil and if we take the vitreous out

and then look at it with these effects

we can create what's called a Tyndall

effect and we can see that in the

e

Anatomy of lens

 what is lens then. we'll cover shape of lens with lens dimensions and terms related to that then we'll look into location of lens that way the lens is situated in the eye and its attachments then parts of the lens and lens structure start with.

what is lens so lens is a transparent a vascular refracting structure in the eye which helps in focusing light rays on the retina and as lens takes part in refraction of light lens should have some power so what is the power of lens and the answer is lens contributes about a one third to the total power of i which is about 15 to 17 diopters next is shape of lens and terms relate to that so shape of lens is spherical at birth and by convex in adults as you can see in this picture the biconvex shape of lens in which the posterior surface is more curved than the anterior surface so here if i talk about radius of curvature of these surfaces then radius of curvature is always inversely proportional to the curvature itself and as anterior surface is less curved or i can say flatter so if i draw a complete circle for this curvature then this would be radius of curvature of anterior surface which is about 10 millimeter and if i make a complete or full circle for posterior surface which is more curved than the anterior surface or i can say steeper then this would be radius of curvature of posterior surface which is about six millimeter and i think now you got it that more curved surface has lesser radius of curvature and less curved surface has more radius of curvature now there are two points to know on interior and posterior surface of lens are anterior pole and posterior pole in which anterior pole is the center of anterior surface and posterior pole is the center of posterior surface and distance between these poles is measured as thickness of lens or entire posterior diameter of the lens which is about three millimeter at birth and increase to about six millimeter in older age so we talked about shape of lens which is by convex but by convex is in cross sectional view if we see lengths from front or back of the eye then lens has a circular shape so length is a combination of two circles interiorly and posteriorly and where these two circles meet we call this as equator of the lens and in cross sectional view we say these two points as equator which is actually a complete circumference now equatorial diameter of lens is about 6.5 millimeter at birth which reaches to 9 to 10 millimeter in adults and it is generally measured in nasal to temporal dimension now how the lens is suspended at its place so the reason for that is the equator of the lens is surrounded by ciliary zonules or called suspensory ligaments which has the one end attached to the lens incomplete 360 degree circumference and the other end is attached to the ciliary processes of ciliary body now we will see location of lens so the basic location of lens is behind the iris and in front of the waitress or can say lens is in contact with aquasumer anteriorly and vitrous humor posteriorly and posteriorly the transparent twitter's gel has a shallow depression in which lens is placed that depression in vitro's gel is known as patellar fossa and there is a little space present between this particular fossa and posterior surface of lens which is known as burgers space or retro lentil space now we know that lens is situated in particular fossa but how is it attached to vitreous gel so the attachment between posterior surface of lens and anterior vitreous is in a circular fashion by a ligament known as vigor's ligament or haloid capsular and the strength of this attachment decreases with age now next is lens structure or parts of lens so histologically lens is basically composed of three structures and these structures are lens capsule anterior lens epithelium and lens fibers which will see each one by one start with lens capsule so when we say.

TARBECULER MASHWORK

we will mainly discuss about the aqueous

humor drainage system.

That is involving the tobacco meshwork so. we will discuss the anatomy of the trabecular meshwork how the equation is getting drained through this tobacco meshwork how you visualize the tobacco measure that is by means of using gonioscopy so we will learn about guneoscopy the various types of gonioscopes how to use them what are the advantages and disadvantages of each okay and how you see the angle structures when you see through the bonus scope so without much delay  so as you know the equation is produced from the ciliary process here okay enters the posterior chamber passes through the pupil and then comes to the anterior chamber fills the anterior chamber and then goes to the angle of the anterior chamber okay so here we have the important structure called as the trabecular meshwork so this will pass through this trabecular meshwork and then there are so many ways through which the equation is getting drained into the venous system so we will see the trabecular meshwork in detail now so what is the little meaning of the trabecular meshwork it is nothing but a beam or the rod which will connect two structures giving support are helping in some function so it is basically like a beam or a rod-like structure okay and this trabecular meshwork is nothing but a connective tissue core which is surrounded by the endothelium so let's discuss about the trabecular meshwork this whole color thing which is shown in this picture is a trabecular meshwork hope you got the orientation so just let me name the parts here this is the scleral spur okay extending here all over 360 degree some part of the ciliary body and then the insertion of the iris and here we have the scleral sulcus okay as the trabecular meshwork gets opposed to the scleral sulcus it converts it into a canal called as slim's canal okay in the trabecular meshwork we have three parts it's like three sheets which are opposing over the scleral sulcus to form the slam scanner the innermost one is the evasculer meshwork the second is the corneus clearer and the third is  canaliculi just go by the name so this is the uvl meshwork which is in opposition to the iris the corneas clearance okay and then the juxta which is around the slams canal so let's see each one now so this is the blue part is the uvl meshwork so this blue colored one is the uvl meshwork it is the innermost part it is in direct contact with the 8-way tumor it is attached here to the ciliary body and the root of iris to the peripheral part of the cornea okay as you can see the pores are not so regularly arranged okay and they're quite big in size it varies from 25 to 75 microns in size okay so this is about the uvl meshwork the second one that is which is shown in the red color is the corner scleral part which is attaching from the scleral spur and opposing and getting attached to the anterior wall of the scleral sulcus okay so this is the attachment of your cornea scleral meshwork so this is in direct opposition to your slums canal so it plays a major role in the drainage of the aqueous humor and as you can see the pore size is decreased compared to the evil measure and it measures about 5 to 15 microns okay and the holes become smaller as it goes near to the canals so here the inner holes are little smaller compared to the outer holes these openings are nothing but the sieve like things which help in the drainage of the aqueous humor and one more important aspect of this corn scleral meshwork is the longitudinal muscles of the ciliary body which i have explained .

IRIS

 Iris anatomy so there's just that it still

has a picture of the iris so there's two

ways to think of anatomy there's the

clinical anatomy and then the histologic

anatomy. So first let's talk about the

clinical anatomy there's two main zones

the pupillary zone and that contains the

see which one's the laser again the

pupil areas on which it contains the

ruff and the reflected or posterior

pigmented area and then you have the

ciliary zone which is on the outside of

the rough it contains Irish crypts and

they're separated by this collar rat

which represents the blood vessels

running through the iris so the other

way to look at it is more east

illogically there's five layers that we

classically talked about the anterior

limiting layer or an anterior border and

that is interrupted by a connective

tissue versus ciliary body then there's

a stroma which is sort of the meat of

the iris that has melanocytes the

vessels and different things that we'll

talking about more detail than the

muscular layer there's the smooth muscle

at the pupillary margin and smooth

muscle deep frier stroma if anterior

pigment epithelium in the posterior

pigment of the killer

there's kind of a cartoon version of

this as you can see this anterior border

the stroma without blood vessels and

then the muscles and the posterior

pigmented area so the anterior border is

condensation of fibroblasts and lanta

sites it's really really dense where you

have the crypts it is absent and from

what I read the reason for that is so

that the aqueous humor can more fully

bathe the stroma in those those crypts

the stroma itself contains pigmented

cells melanocytes clump cells

fibroblasts collagen hyaluronic acid

blood vessels are the nerves

mixed with the muscular layer this is

kind of the bulk of the iris matter that

we get medical school is that there's

the sphincter pupil a and the dilator

valuator is more sexual more medial and

this being the sanctum where media on a

dilator is more lateral and you can see

in this drawing the way that the fibers

run

so if smooth muscle is autonomic

innervation and they're derived from the

anterior pigment layer of the iris so

I'm gonna touch on this a little bit I

think it's gonna be explained in more

detail when we talk about some of the

abnormal findings but the dilator

muscles innervation sympathetic

innervation of one adrenergic

stimulation starts an ipsilateral

hypothalamus synapses to the t1 level of

spinal cord and then it travels from the

spinal cord over the pulmonary apex

which is something we always think about

with thoracic outlet syndrome in

it's like that and then it runs up the

superior cervical ganglion and runs

along the internal carotid plexus

through the cavernous sinus and then the

ophthalmic division of clay on their v

to the dilator muscle and then there's

also some parasympathetic innervation

that's inhibitory the sphincter muscle

is parasympathetic mostly with the

muscarinic receptors starts an editor

Westphal nucleus runs to cranial nerve

three through the cavernous sinus the

superior oblique branches to the

super-quick muscle and synapses in

ciliary ganglion and it then terminates

the short cilia nerve to die restrictor

and you see the sympathetic innervation

there that helps inhibit the sneaky

muscles so then interior pigment my

epithelium specialized myopathy all

cells the apex is of the anterior

posterior face each other and the bases

face out it's continuous at the

pigmented epithelium of the ciliary body

one thing dr. mammals always talks about

in path reads is the way to tell between

the iris and the ciliary body is the

iris has two pigmented layers that you

can't differentiate whereas the ciliary

body just has the one so this just

continues with the pigment tests earlier

body layer then you have posterior

pigment epithelium this is the part you

see coming t

Sclera

 Thus clearer also known as the white of

the eye is the opaque fibrous protective

outer layer of the eye containing

collagen and elastic fiber in humans the

whole scarer is white contrasting with

the colored iris but in other mammals

the visible part of the sclera matches

the color of the iris so the white part

does not normally show in the

development of the embryo.

The scarer is

derived from the neural crest in

children it is thinner and shows some of

the underlying pigment appearing

slightly blue in the elderly fatty

deposits on the scarer can make it

appear slightly yellow the human eye is

relatively rare for having an iris that

is small enough for its position to be

plainly visible against the scarer this

makes.

It easier for one individual to

infer where another individual is

looking under cooperative eye hypothesis

suggests this has evolved as a method of

nonverbal communication structure the

scarer forms the posterior 5/6 of the

connective tissue coat of the globe it

is continuous with the dura mater and

the cornea and maintained the shape of

the globe our offering resistance to

internal and external forces and

provides an attachment for the extra

ocular muscle insertions the scarer is

perforated by many nerves and vessels

passing through the posterior scarole

foramen the hole that is formed by the

optic nerve at the optic disk the outer

two thirds of the sclera continues with

the dura mater V of the dural sheath of

the optic nerve the inner third joins

with some choroidal tissue to form a

plate across the optic nerve with

perforations through which the optic

fibers pass the thickness of the scarer

varies from 1 millimeter at the

posterior pole to 0.3 millimetres just

behind the rectus muscle insertions the

scarers blood vessels are mainly on the

surface along with the vessels of the

conjunctiva those in the episteme

a render the inflamed eye bright red in

many vertebrates the scarer is

reinforced with plates of cartilage a

bone together forming a circular

structure called the sclerotic ring in

primitive fish this ring consists of

four plates but the number is lower in

many living Bray fin fishes and much

higher in lobe-finned fishes various

reptiles and birds the ring has

disappeared in many groups including

living amphibians some reptiles and fish

and all mammals the eyes of all

non-human primates a dark with small

barely visible sclera histology the

collagen of the sclera is continuous

with the cornea from outer to inner most

the four layers of the scarer are a piss

clearer

stroma lamina fusca endothelium the

scarer is Oh peg due to the irregularity

of the type one collagen fibers as

opposed to the near uniformed thickness

and parallel arrangement of the corneal

collagen

moreover the cornea bears more

mucopolysaccharides

to embed the fibrous the cornea unlike

the sclera has five layers the middle

thickest layer is also called the stroma

the sclera like the cornea contains a

basal endothelium above which there is

the lamina fusca containing a high count

of pigment cells sometimes very small

grey blue spots can appear on the sclera

a harmless condition called scarole

melanocyte ptosis function human eyes

are somewhat distinctive in the animal

kingdom in that the sclera is very

plainly visible whenever the eye is open

this is not just due to the white color

of the human sclera which many other

species share but also to the fact that

the human iris is relatively small and

comprises a significantly smaller

portion of the exposed eye surface

compared to other animals it is

theorized that this adaptation evolved

because of our social nature as the

I became a useful communication tool in

addition to a sensory organ it is

believed that the conspicuous carer of

the human eye makes it easier for one

individual to infer where another

individual is looking increasing the

efficacy of this particular form of

nonverbal communication animal

researchers have also found that in the

course of the domestic.