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.

AQUEOUS HUMOR

 Aqueous humor and its production volum the aqueous humor as a clear watery fluid filling the anterior chamber 0.25 milliliters and posterior chamber 0.06 milliliters of the eyeball functions of aqueous humor are it maintains a proper intraocular pressure it plays an important metabolic role by providing substrates and by removing metabolites from the avascular cornea and lens it maintains optical transparency.

It takes the place of limp that is absent within the eyeball refractive index of aqueous humor as 1.33 6 composition constituents of normal aqueous humor are on water 99.9 and solids 0.1 percent which include proteins colloid content because of blood aqueous barrier the protein content of aqueous humor 5 to 16 milligrams % is much less than that of plasma 6 to 7 GM percent however in inflammation of UV EA irid osek lightest the blood aqueous barrier is broken and the protein content of aqueous has increased plasmoid aqueous amino acid constituent of aqueous humor as about 5 milligrams per kilogram water oxygen is present in aqueous in dissolved state note thus composition of aqueous is similar to plasma except that it has high concentrations of ascorbate pyruvate and lactate and low concentration of protein urea and glucose aqueous humor anterior chamber versus posterior chamber the composition of accuse humor in anterior chamber differs from that of the aqueous humor in posterior chamber because of metabolic interchange the main differences are in posterior chamber aqueous is higher than in the anterior chamber CL concentration in posterior chamber is lower than in the anterior chamber ascorbate concentration of posterior aqueous is slightly higher than that of anterior chamber aqueous production aqueous humor is derived from plasma within the capillary network of ciliary processes.

The normal aqueous production rate is 2.3 micro liters per minute the three mechanisms diffusion ultra filtration and secretion active transport play a part in its production at different levels the steps involved in the process of production are summarized below one ultra filtration first of all by ultra filtration most of the plasma substances pass out from the capillary wall loose connective tissue and pigment epithelium of the ciliary processes thus the plasma filtrate accumulates behind the non pigment epithelium of ciliary processes to secretion the tight junctions between the cells of the non pigment epithelium create part of blood aqueous barrier certain substances are actively transported secreted across this barrier into the posterior chamber the active transport is brought about by na+ k+ activated ATPase pump and carbonic anhydrase enzyme system substances that are actively transported include sodium chlorides potassium ascorbic acid amino acids and bicarbonates 3 diffusion active transport of these substances across the non-pigmented ciliary epithelium results in an osmotic gradient leading to the movement of other plasma constituents into the posterior chamber by ultra filtration and diffusion sodium is primarily responsible for the movement of water into the posterior chamber control of aqueous formation the diurnal variation in intraocular pressure certainly indicates that some endogenous factors do influence the aqueous formation the exact role of such factors as yet to be clearly understood vasopressin and adenyl cyclase have been described to affect aqueous formation by influencing active transport of sodium ultra filtration and diffusion the passive mechanisms of aqueous formation are dependent on the level of blood pressure in the ciliary capillaries the plasma osmotic pressure in the level of intraocular pressure drainage of aqueous humor aqueous humor flows from the posterior chamber into the anterior chamber through the pupil against slight physiologic resistance from the anterior chamber the aqueous is drained out by two roots one trabecular conventional outflow.

Schlemms canal

 Schlemms canal is a circular lymphatic like

vessel in the anterior chamber the collects aqueous humor from the anterior chamber and delivers it into the Epistle blood vessels via a quiz veins it is named after Friedrich slab a German anatomist the canal is essentially an endothelium line tube resembling that of a lymphatic vessel on the inside of the canal nearest to the aqueous humor it is covered by the trabecular meshwork this.

Anterior chamber

 Anterior chamber problems can lead to a

red eye the anterior chamber of the eye

is literally a chamber at the front of

the eye containing aqueous humor it is

bounded by the cornea anteriorly and the

iris and lens posteriorly.

The anterior chamber can be described as

deep or shallow in this case it is deep

the anterior chamber has an angle 360

degrees around where the iris and cornea

meet the angle contains important

structures called the trabecular

meshwork and schlemm's canal which can

drain aqueous humour from the eye these

microscopic structures are not visible

in this photo the limbus is an external

landmark it is the transition zone where

the clear cornea blends in transitions

into the white sclera the anterior

chamber is filled with aqueous humor.

aqueous humour is produced behind the

iris by epithelium covering the ciliary

body the aqueous humor circulates over

the anterior lens making its way through

the iris lens channel into the anterior

chamber and it eventually it exits the

anterior chamber through the angles

drain acute angle closure glaucoma is in

the differential diagnosis of red eye

let's see how the anterior chamber leads

to the red eye in this disease in most

eyes

the iris meets the cornea so the angle

they make together is wide open at 45

degrees in this situation the drainage

structures in the angle are easily

accessed by the exiting aqueous humor in

semis the lens is bigger than average

and located more anteriorly in the eye

as seen in the figure on the right this

combination of lens size and location

pushes the iris forward this in turn

leads to a shallower anterior chamber

and narrower angle opening in this

example only 25 degrees as a person age

of the lens grows fatter which can lead

to narrow our angles

in an ice starting out with a narrow

angle acute angle closure is triggered

by a dilated pupil here's why in a

dilated pupil the peripheral iris

becomes thicker which takes up more

angle space also there's greater contact

between iris and the lens and in fact

the iris can get stuck to the lens

which then blocks the natural aqueous

humor pathway aqueous humor volume

increases behind the iris and eventually

it pushes the peripheral iowa's forward

completely closing the angle aqueous

humor cannot leave the eye and is

continuously produced which leads to

very high levels of high pressure this

high level of eye pressure and acute

angle closure is extremely painful and

is frequently associated with nausea and

vomiting

the high pressure leads to congestion of

blood vessels over the entire surface of

the eye hence the red eye this is a

clinical picture of acute angle closure

showing the mid dilated pupil which

triggers the angle closure process the

pupil will be non-responsive to light

because the very high pressure causes

necrosis of the iris sphincter the photo

also shows diffuse dilation of

conjunctiva blood vessels

this photo highlights the other findings

an acute angle closure attacks the

anterior chamber is shallow seen here is

very little space between the two beams

of light on the left one highlighting

the cornea and the other immediately

behind it shining on the iris

there is also corneal edema seen as

subtle wrinkles in the cornea edema is a

result of high pressure driving aqueous

humor into the spongy cornea hyphema is

another red eye problem of the anterior

chamber and blunt trauma is frequently

the cause of the hyphema let's say you

have the pebble flying towards the eye

once it hits the cornea it compresses

the eye in the anterior posterior

direction which is the direction of the

blue arrow at the same time the eye

expands in the opposite direction shown

with the black arrows if we turn the eye

from the previous slide around so that

we are looking the iris base on we see

it if the force is shown by the black

arrows in the previous slide are

stretching the eye radially from the

limbus an eye that has just been hit

will become red from traumatic

inflammation the cornea.

Cornea

cornea

Cornea is the  clear window that lets light into the front of your eye. we are  going to explore several of its amazing properties first it is made out of the  same tissue as your skin so how is it  the cornea can be so clear second optically speaking the cornea supplies more than half of the focusing power of  the eye third the shape of the cornea has to be  perfectly smooth and properly curved to make the high quality image that falls  on the retina we will explore all these features in detail looking at the front of the eye .

Some parts are easy to identify you can see the iris the colored part and the pupil the round  hole in the middle of the iris the  cornea however is so clear it can only  be seen by the light reflecting off its surface this is the view we get looking through the microscope that we use to examine the eye the pupil is widely dilated with a slit beam of light passing through the cornea and lens each is outlined with dashed lines to make them easier to identify in diagram view the cornea is like the crystal of a watch arching over the iris in the center of the iris is the pupil which changes size to regulate the amount of light entering the eye and behind the iris is the natural lens like the lens in a camera  if the slit beam view was confusing at  first it should now make more sense you  can see the curved shape and thinness of  the cornea separated by a space then the rounded shape and thickness of the normal lens in the adult the average  cornea is 12 millimeters wide thickness  in the centre is half a millimeter at the edge 0.7 millimeters think about  that only half a millimeter thick  looking closer at the cornea we are taking a section and magnifying it  showing it has three distinct layers on  the outer surface is the epithelium a  lot like the surface layer of your skin  The middle layer the stroma occupies  most of the thickness of the cornea providing its shape and structural  integrity lining the inside is the  endothelium a single layer of cells that  pump fluid out of the cornea keeping it  dry and clear looking through a regular microscope you can see the actual  corneal layers and the fine cellular details we will now work our way from  front to back in detail the first thing that light encounters as it reaches your  eye is the tear film on the surface of the cornea a good-quality tear film is  important for clear vision comfort and  corneal health the tear film needs to be smooth and even say glassy as the first step of making a clear image if it is  not smooth then light is scattered and vision is reduced the tear film is more complicated than you might guess magnifying the section in the orange circle shows the tear film has three layers on the surface of the cornea is a  layer of mucus that allows the watery part to spread out over the cornea in the middle is the aqueous or watery layer on the outer surface is a layer of  oil which helps reduce evaporation so  the tear layer is more complicated and more important than you might have thought back at the microscope view we  see the outer surface layer of the cornea the epithelium in this closer  view you can see the individual cell layers which are labeled epithelial  layers typically rest on a basement  membrane that is important because that is where the epithelial layer makes its attachment to the cornea the epithelial layer is derived from the same tissue as  your skin so it behaves much like your  skin how is that  the action begins in the column shaped basal layer of cells these cells divide  and move upward into the middle layer where they take on a more flattened  wing-like shape then they reach the surface and after a short while they are Slough tauf just like dead skin cells this process takes about seven to ten days meaning the surface cells are replaced just about every week.

The Human Eye

 The human eye.

The human eye is the most

valuable and sensitive sense organ and

it is a natural optical instrument the

eye is nearly spherical in shape with a

slight bulge in the front part and it

enables us to see the beautiful colorful

world around us let us discuss about the

important parts of the eye and the

functions.

 

Cornea the front part of the

eye is covered by transparent spherical

membrane called cornea light enters the

eye through Cornea, iris just behind the

cornea is a dark colored muscular

diaphragm which has a small circular

opening in the middle pupil.

 Pupil is a small circular opening of iris the pupil

appears black because no light is

reflected from it the dark center in the

middle of the iris the pupil determines

how much light is let into the eye

it changes sizes to accommodate for the

amount of light that is available the

iris regulates the light by justing the

size of the pupil let us see how iris

regulates and controls the amount of

light entering the eye when the

intensity of light is more or if it is a

bright source of light then the iris

makes the pupil to contract and as a

result the amount of light entering the

eye decreases when the intensity of

light is less or if the light is dim.

Then the iris dilates the pupil so that

more light can enter the eye islands the

islands is a convict land made of

transparent jelly-like proteinaceous

material the eye lens is hard at the

middle and gradually becomes soft

towards the outer edges the eye lens is

held in position by ciliary muscles the

ciliary muscles help in changing the

curvature and focal length of the

islands retina in the back surface of

the eyeball is called retina it is a

semi-transparent membrane which is

light-sensitive and is equivalent to the

screen of a camera the light-sensitive

receptors of the retina are called rods

and cones when light falls on these

receptors they send electrical signals

to the brain through the optic nerve the

space between the retina and islands is

filled with another fluid called

vitreous humour blind spot it is a spot

at which the optic nerve enters the eye

and is insensitive to light and hence

the name let us discuss about

Accommodation of the eye and power of

accommodation accommodation of the eye

the process by which the ciliary muscles

changed the focal length of an eye lens

to focus distant or near objects clearly

on the retina is called the

accommodation of the eye power of

accommodation the ability of the eye to

focus objects lying at different

distances is called the power of

accommodation of the eye how does an eye

focus objects at varying distances when

the ciliary muscles are relaxed the

islands becomes thin thus its focal

length increases and we see the distant

objects clearly when the ciliary muscles

are contract then the curvature of the

islands increases and the islands

becomes thick thus its focal length

decreases and we see the nearby objects

in brief it is adjustment of the focal

length of the eye lens which enables us

to focus on objects situated at

different distances least distance of

distinct vision near point near point or

least distance of distinct vision is a

point nearest to the eye at which an

object is visible distinctly for a

normal eye the least distance of

distinct vision is about 25 centimeters

however it varies with age of the person

for example for infants it is only 5 to

8 centimeter the far point of the eye

far point of the eye is a maximum

distance up to which the normal eye can

see things clearly it is infinity for a

normal eye cataract the crystalline lens

of people at old age becomes milky and

cloudy this condition is called cataract

this causes partial or complete loss of

vision it is possible to restore vision

through a cataract surgery range of

vision the distance between the near

point and the far point is called the

range of vision.

انکاس

  تاریخ کے بارے میں کچھ دلچسپ حقائق جن کی مجھے امید ہے کہ آپ کے سفر میں اضافہ ہوگا۔

 انکاس کون تھے؟  یہ جنوبی امریکہ کے مقامی باشندے تھے جو اپنے زمانے میں امریکہ کی ایک سب سے بڑی اور امیر ترین سلطنت کے حکمران تھے۔ جو کچھ بھی  ان کے بارے بیان کیا  جاتا ہے وہ زبانی روایت ہے، ان کی ثقافت کی باقیات جیسے پتھر ، مٹی کے برتن ، سونے اور چاندی کے زیورات اور لوگوں کی ٹیپسٹری میں بنی ہوئی چیزوں کے ذریعے پردہ اٹھا دیا گیا ہے۔

 انکاس نےکوئی تحریری زبان تیار نہیں کی جس سے یہ بات دلچسپ ہو جائے کہ وہ اتنے بڑے علاقے کو کنٹرول کرنے اور ان کا انتظام کرنے کے اہل تھے ۔  انکاس نے سیکڑوں مختلف قبائل کے لوگوں پر حکومت کی جو سب  اپنی اپنی زبان بولتے تھے ۔  وہ اپنے معاشرے کو منظم کرنے کے جدید ترین طریقوں کو تیار کرکے اپنے کنٹرول میں رکھنے میں کامیاب ہوگئے تھے ۔  انہوں نے محسوس کیا کہ ایک بڑی فوج کو برقرار رکھنے ، اور بہت ہی اعلی درجے کی زرعی ، عمارت اور انجینئرنگ کے طریقوں کی ایجاد کے ذریعہ کہ وہ ایک مضبوط قوم بن سکتے ہیں۔

 انکاس کی اہم ایجادات جن میں پتھر کی سڑکیں اور بہت سے پل  ہیں ۔ جو انہوں نے ملک کے تمام حصوں کو مضبوط کرنے کے لئے بنائے ہوئے تھے۔

 جو علاقے انکاس نے فتح کیے ان سب کی  زبان سیکھنے اور بولنے پر مجبور ہوگئے تھے  ، پھر انہوں نے ایک مشترکہ زبان کی وجہ سے  سلطنت میں مواصلات کو  آسان بنایا ۔

 سب سے پہلے انکا روڈ سسٹم ایک قابل ذکر بات ہے کیونکہ یہ کولمبیا سے قبل کا سب سے وسیع روڈ کا نظام ہے۔  یہ سوچ کر حیرت ہوتی ہے کہ انہوں نے ایک روڈ سسٹم بنایا  جو تقریبا  چودہ ہزار میل لمبا ہے ۔ جس میں سے کچھ سمندر کی سطح سے سولہ ہزار  فٹ سے زیادہ اونچائی حاصل کرنے والے اینڈیس پہاڑ بھی شامل ہیں۔   جب آپ اس ثبوت پر غور و فکر کریں گیں کہ انکاس نے پہیے کو نقل و حمل کے لئے استعمال ہی نہیں کیا تھا اور یہ کہ سولہویں صدی تک ان کے پاس گھوڑے بھی نہیں تھے ، یہ بات ناقابل یقین ہے کہ پگڈنڈی صرف چلنے کے لئے استعمال کی جاتی تھی  سامان کی آمدورفت کےلئے نہیں۔

 آرام اور ناشتے کی غرض کےلئے  اندازے کے مطابق 2 ہزار ہوٹلز موجود تھیں ، جو پگڈنڈیوں کے ساتھ ساتھ وقفے وقفے پر بنائی گئیں۔  ان ہوٹلز میں  جانوروں ، عام طور پر لاماموں کے لئے بھی آرام اور خوراک کا بھی انتظام تھا ۔  وادیوں تک رسائی حاصل کرنے کے لئے رسی کے پل بنائے گئے تھے۔  سڑکوں پر سفر کرنے والے دسیوں ہزاروں افراد کو کھانا ، رہائش اور فوجی سامان کی سہولت میسر تھی ۔  کزکو ، انکا کیپیٹل شہر کے ساتھ ایک پگڈنڈی کے ذریعے سلطنت کے وسط میں ملتے تھے ۔

 مکا پچو تک انکا ٹریل۔امریکا  کا پاک نین ٹریل سے  زیادہ مشہور انکا ٹریل ہے کیونکہ اس سے اولانٹائیتمبو اور ماچو پچو ، جو "انکاس کا گمشدہ شہر" جاناجاتا ہے گاؤں کی طرف جاتا ہے۔  اس راستے میں بہت سارے محفوظ کھنڈرات بھی موجود ہیں اور وہ یہ کہ اینڈیس پہاڑی سلسلے اور امازونیہ برساتی جنگلات کے کچھ حصوں سے گذرنے کے ساتھ ہی پورے تجربے سے سحر انگیز محسوس ہوتا ہے ۔  اپنے حیرت انگیز سفر کے بعد آپ کو 'سن گیٹ' اور مچو پچو کے داخلے کا سامنا کرنا پڑتا ہے ۔  جب مچو پچو بنا ہوا تھا تو انکا امپائر 1450 کے آس پاس اپنے عروج کو پہنچا ہوا تھا ۔  کہانی یہ ہے کہ ہسپانوی فتح کے وقت سلطنت کا خاتمہ ہوا اور 100 سال سے بھی کم عرصے بعد مچو پچو کو ترک کردیا گیا۔

 ہسپانویوں نے مچو پچو کو آباد کرنے کا انتظام نہیں کیا ، اور یہ دوبارہ جنگل بن گیا  کیونکہ یہ انکا کی بہت سی سائٹوں کی طرح محفوظ ہے۔  صرف بہت ہی کم لوگوں کو اس کے وجود کا علم تھا اور سلطنت کو یائل مورخین اور ایکسپلورر ہیرام نے 1911 میں دنیا کے تصور میں لوٹا دیا۔

فرینکلن

  خوبیوں کی فہرست بنائی ، ہر ایک کو ایک صفحے پر تحریر کیا۔  ہر ایک خوبی کے تحت اس نے ایک خلاصہ لکھا جس نے اسے مکمل معنی بنا دیا ۔  پھر انہوں نے ایک مدت کے لئے ہر ایک پر عمل کیا۔

 ان خوبیوں کو عادت بنانے کے لئے ، فرینکلن اپنے روزمرہ کے کاموں پر خود کوترجیح دینے کے لئے ایک طریقہ کار کو واضح کیا۔  ایک جریدے میں انہوں نے ہر خوبی کے لئے ایک قطار اور ہفتے کے ہر دن کے لئے ایک کالم تیار کیا۔  جب بھی وہ غلطی کرتے تھے ، اس کےلئے مناسب کالم میں ایک نشان بنایا ہوا تھا۔  ہر ہفتے انہوں نے اپنی توجہ ایک مختلف خوبی پر مرکوز کی۔  وقت کے ساتھ ، مشق کے ذریعے ، انہوں نے سوچا کے  ایک دن وہ اپنے تجربات کو ایک کتاب کی شکل دینے  کے بارے میں سوچا ۔

 ان کا کہنا ہے کہ انہوں نے یہ ذاتی امتحان برسوں سے جاری رکھا ۔  کام کو اچھی طرح سے کرنے کے لئے انہوں نے ہر ایک خوبی اور اس کی اہمیت کا ایک چوتھائی - وقت میں  کرنے کی کوشش کی۔  اس مشق کا  آغاز مزاج سے ہوا ، جس میں ناپسندیدہ عادات کی نشوونما کرنے کے لئے اور ہر خوشی اور غم  کو بھی شامل کیا گیا ، کیونکہ مزاج "اس حد تک ٹھنڈک اور کلیئرنس کرتا ہے جو اس قدر ضروری ہے جہاں مستقل چوکسی برقرار رکھنی ہو اور غیر متوقع کشش کے خلاف محافظ رکھا جائے۔   تو قدیم عادات اور مستقل فتنوں کی طاقت کو کنٹرول کیا جا سکتا ہے ۔ 

 فرینکلن کے ذریعے مشق  ہونے والی دوسری خوبیوں میں خاموشی ، نظم و ضبط ، قرارداد ،احسان مندی  ، خلوص ، انصاف ، اعتدال ، صفائی ، سکون ، عفت اور عاجزی تھی۔   انہوں نے ہر دن اپنا وقت استعمال کرنے کی تھوڑی سی اسکیم پر عمل کیا۔  ہر صبح پانچ سے سات تک وہ جسمانی ذاتی توجہ میں گزارتے ، ایک مختصر دعا کہتے ، دن کے کاروبار اور قراردادوں پر سوچتے ، ناشتہ مطالعہ کرتے اور کھاتے۔  آٹھ سے بارہ تک انہوں نے اپنی تجارت میں کام کیا۔  بارہ سے ایک تک انہوں نے اپنے اکاؤنٹس کو پڑھا اور کھانا کھایا۔  دو سے پانچ تک انہوں نے اپنی تجارت میں کام کیا۔  شام کے 10 بجے تک انہوں نے موسیقی میں گزارے۔

 اس وقت چیزوں کو ان کی جگہوں پر ڈالنے کے لئے بھی استعمال ہوتا ہے۔  ریٹائرمنٹ سے پہلے آخری بات میں اس دن کا امتحان تھا۔  79 سال کی عمر میں ، انہوں نے اپنی صحت کو مزاج کے مطابق بنا لیا۔  صنعت اور بدگمانی کو بدقسمتی کا حصول؛  اخلاص اور انصاف پر اپنے ملک کا اعتماد۔

 زندگی اور سیاست میں فرینکلن کی غیر معمولی کامیابی کا انحصار ان کی ذاتی ذمہ داریوں پر قابو پانے کے لئے ان کی استقامت ، اور اس کی مستقل طور پر بہتر ہونے کی خواہش کو قرار دیا جاسکتا ہے۔

 اگلی بار جب آپ واقعی کچھ حاصل کرنا چاہتے ہیں تو ، اپنی ذاتی جریدے پر توجہ دینے کے لئے وقت نکالیں۔  آپ کا کون سا فتنہ ہے جو عظمت کے راستے میں روکاوٹ ہے؟  کامیاب بننے کی عادت بنانے کے لئےآپ کیا کرسکتے ہیں؟

جسمانی تکالیف

کسی جسمانی تکلیف یا بیماری کی علامت ،  یا جذباتی پریشانی کی علامت کے طور پر درد کی وضاحت  آسانی سے کی جاسکتی ہے۔  ہلکے درد کا علاج کئی طریقوں سے کیا جاسکتا ہے… ادویات کے ذریعے اور روحانی علاج کے ذریعے قدرتی جڑی بوٹیوں کے ذریعے۔  لیکن اگر درد دائمی اور ناقابل برداشت ہو تو کیا ہوگا؟  اسکے لئے بھی  دوائیں ملتی ہیں۔  ادویات کا اثراچھی طرح سے ہوتا ہے۔  مگرکچھ لوگوں کے لئے  دائمی درد کے ساتھ ، NLP طریقہ علاج بہت اچھی طرح اثر انداز ہوتاہے۔

 این ایل پی کیا ہے؟  یہ نیورو لسانی پروگرامنگ ہے۔  دماغ اور زبان کے مابین تعلق کو بیان کرنے کے لئے این ایل پی کے  اصولوں کا ایک مجموعہ استعمال کیا جاتا ہے۔  اگرچہ ابتدائی طور پر این ایل پی کے ساتھ درد کے علاج کے بارے میں کافی  شکوک شبہات پاۓ جاتے تھے  لیکن اب طبی طبقہ کی رائے ہے کہ این ایل پی طریقہ علاج واقعی درد پر قابو پانے میں معاون ہے۔

آئرلینڈ

 جب لوگ آئرش اور آئرلینڈ کا ذکر سنتے ہیں ، تو وہ فورا  ہی یادکرتے ہیں وہاں کے کلچر کے بارے میں اور دل ہی دل میں لطف اندوز بھی ہوتے ہیں: سینٹ پیٹرک ڈے ، گرین بیئر ، چار پتی کلوز اور لیپریچنس۔  یہ سبھی آئرش کلچر کا ایک بھرپور حصہ ہیں ، لیکن زمرد آئل کے پاس گرین بیئر اور لیپرچین کے علاوہ اور بھی بہت کچھ ہے۔

 سرسبز و شاداب پھیلاؤ کی وجہ سے آئرلینڈ "زمرد آئل" کے نام سے بھی جاناجاتا ہے ، جو ہر کسی کو اپنی طرف کھینچتا ہے ، اور اس کی دھوپ کو ہر کویئ انجواۓ کرنا پسند کرتا ہے۔ آئرلینڈ کو دو حصوں میں تقسیم کیا گیا ہے: جمہوریہ آئرلینڈ اور شمالی آئرلینڈ۔  شمالی آئرلینڈ برطانیہ کا ایک حصہ ہے جس کی تخمینہ لگ بھگ آبادی 20 لاکھ افراد پر مشتمل ہے۔  اب آبادی میں 1960 کی دہائی میں انکے اندرونی معملات بہت خراب تھے اسکے باوجود  بہت بڑی بہتری آئ ہے۔ پوری تاریخ میں اس خطے میں سیاسی اور مذہبی تنازعات کا مسلہ رہا۔  تاہم ، تمام تنازعات نے اس خطے کی ثقافتی خوشحالی میں بہت اضافہ کیا ہے۔

 آئرش قوم ایک پُرجوش ثقافتی اور تاریخی پس منظر کی حامل قوم ہے۔  وہ ایک لمبے عرصے سے وہاں مقیم ہیں اور اپنے سلسلے کو سیلٹ کے سلسلے سے جوڑتے ہیں۔  آئرش قوم ثقافت اور مذہب میں بٹی ہوئ قوم ہے۔ انکی زیادہ تر آبادی بنیادی طور پر پروٹسٹنٹ اور کیتھولک پر مشتمل ایک مرکب ہے۔  سیاسی طور پر وہ نیشنلسٹوں اور یونینسٹ کے درمیان بہت لڑائ جھگڑے ہوتے ہیں۔  اس تقسیم کی وجہ سے آئرش قوم کے فنی ، مذہبی ، سیاسی اور فلسفیانہ جذبات کو بہت متاثر کیا ہے۔

 شمالی آئرلینڈ کے مشرقی ساحل کی طرف بیلفاسٹ کا دارالحکومت واقع ہے۔  اس علاقے کا یہ سب سے بڑا گنجان آباد علاقہ سمجھا جاتا ہے۔  یہ برطانیہ میں15 ویں نمبر پر بڑا شہر ہے۔  اس شہر کا جو مقصد تھا وہ  لاطینی زبان میں لکھا ہوا ہے اور اس میں "پرو ٹینٹو کوئڈ ریٹریبیمس" لکھا گیا ہے۔  یہ جملہ جو زبور کی بائبل کی کتاب سے لیا گیا ہے اور اس کا آسان سا ترجمہ کیا گیا ہے: "اتنے بدلے میں ، ہم کیا دیں گے؟"

 بیلفاسٹ شہر جو کہ متاثر کن جدید اور متواتر فن تعمیر کا مرکزہے جیسا کہ بیلفاسٹ کیسل اور بیلفاسٹ واٹر فرنٹ ہال وغیرہ۔  بیلفاسٹ آئی اور خوفناک ڈھانچے نے شہر کو خوش نما رنگ بخشا ہے۔  بیلفاسٹ اور شمالی آئرلینڈ کے لوگ یورپی یونین اور باقی دنیا کے دوسرے ممالک کی طرح فٹ بال کا بہت شوق رکھتے ہیں۔ اس شہر کے لوگوں کو گیلک فٹ بال کا  کھیل سب سے زیادہ پسندہے۔

 شمالی آئرلینڈ  ایک بہت ہی خوبصورت ملک ہے ، جہاں دھند سے لدے ہوۓپہاڑ موجود ہیں کھیل کے لئے بہت اچھی جگہ ہے۔ 

Thomas Garrett

 The last stop on the Underground Railroad was at the home of a Quaker merchant named Thomas Garrett on Shipley Street in Wilmington, in the slaveholding state of Duluth. About 2,700 fugitive slaves were given safe harbor there before moving on to the free states of Pennsylvania and New Jersey.

Garrett's deep commitment to ending slavery would cost him a great deal during his lifetime. Maryland authorities continued to offer a $10,000 reward for his capture. A federal court fine in 1848 bankrupted him, forcing him to turn to his abolitionist friends in the charity business. During the Civil War, his life was in such constant danger that he had to be protected by African-American volunteers. But during his ordeal, Garrett never wavered from his principles of slaveholding or the evils of slavery.

Although Thomas Garrett is recognized today as one of Delaware's most respected citizens, he was actually born in August 1789 in Upper Darby, Pennsylvania. Garrett's parents hid runaway slaves on the family farm at an early age and admitted them out of respect for human freedom. When Garrett was young, the family servant was kidnapped and forced into slavery. Garrett manages to track down and employ a friend of the family and effect an escape, but the incident leaves an indelible impression.

He moved to Wilmington, Delaware, in 1822, but his personal beliefs and deep commitment to his Quaker religious beliefs put him at odds with the state's pro-slavery stance. It was only a few years before Garrett once again resumed his efforts to aid escaped slaves. For the next 40 years, he did everything in his power to do so.

In 1848, Garrett and his partner were convicted of helping the Hawkins family escape from slavery in Maryland. There was also a bank-breaking fine, which would have left the two friends virtually destitute, handed down by U.S. Chief Justice Roger Taney at the Delaware Courthouse in Newcastle. After the sentence was read, a disgusted Garrett gave a speech so moving that even a slaveholding juror offered him his hand: "I say to you and to everyone in this courtroom that, if you know a fugitive who wants asylum, send him to Thomas Garrett, and he will befriend him."

Garrett continued to fight inequality after the end of the Civil War, working as an advocate for the rights of former slaves. When the 15th Amendment was passed in 1870, giving African-Americans the right to vote, its grateful supporters drove Garrett into the streets.Some people even referred to it as "Moses's Out."

On January 18, 1871, Thomas Garrett died. His funeral was attended by all his friends who had participated with him in the freedom struggle. Garrett's body was respectfully conveyed to his final resting place. Wilkeman was held at the Friends' Meeting House on Fourth and West Streets in Coker Hill.