anat iind internal 2nd semester

7/26/2019 Anat IInd Internal 2nd Semester

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Choroid

Post part of vascular coat of the eyeball.

Prime function : nutrition.

Extends from optic disc to ora serrata

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Choroid

Inner surface smooth, brown and lies in

contact with pigment epithelium of retina.

Outer surface: rough and lies in contact with

the sclera.

Avg. about .25mm in thickness

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Choroid

Consist of 3 layers.

- Choriocapillaries the inner most layer.

- Stroma.

- Supra choroidal lamina outer layer

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Supra choroidal lamina

Thin 10-34 micron

Contains of collagen fibers , melanocytes and

fibroblast.

Continuous with supra ciliary lamina of ciliary body.

Space between this membrane and sclera is calledsupra choroidal space

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Stroma

Consist of loose collagenous tissue, pigmentcells, macrophages, mast cells, plasma cellsand lymphocytes.

Main bulk is by vessels in 2 layers

- Outer layer of larger vessels: Hallers layer.

- inner layer of medium vessels: Sattlers layer

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Choriocapillaris

Sattlers layer connect with the

choriocapillaries.

Lying in the single plane beneath RPE.

Rich in capillary network.

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Choriocapillaries

Vessels walls thin with fenestration esp. thesurface facing the retina.

Fenestrated capillaries contain endothelialcells joint by Zonular occludents.

Endothelial cells lined by basementmembrane containing pericytes.

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Bruch's Membrane

Innermost layer of the choroid.

Lies between Choriocapillaries and RPE.

Defects occur spontaneously in myopes ,in

trauma.

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Blood supply of Uveal tract

Supplied by 3 sets of arteries

a. Short post ciliary artery

b. Long post ciliary arteries

c. Ant ciliary arteries.

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Short post ciliary artery

Aries as two trunks.

Each from ophthalmic artery.

Pierce through sclera around the optic

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Long post ciliary arteries

Two in no. Nasal and temporal

Pierce the sclera obliquely on medial andlateral side of optic nerve and to supra

choroidal space

And to ciliary body

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Ant ciliary arteries

Derived from muscular branch of ophthalmic artery.

7 in no. 2 each from artery of SR, IR,and MR muscles.

Pass ant to sclera, limbus and conjunctiva and thenenter ciliary muscle where they anastomose with 2long post ciliary arteries

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Venous Drainage

Ant ciliary veins.

Smaller veins from sclera.

Vortex veins or post ciliary veins

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Smaller veins from sclera

Correspond to the sclera branches of short

ciliary arteries.

Carry blood only from sclera and not from

Choroid.

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Ant ciliary veins.

Tributaries of muscular veins.

Carry blood only from ciliary muscle.

Smaller from corresponding arteries.

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4 in no. sup. Inf, Nasal and Termporal.

Pierce sclera obliquely on each side of SR and IR

6mm behind

Sup temporal vein more post about 8mm

Inf temporal most ant 5.5 mm behind the equator

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Drains blood from:

- whole Choroid.

- Receive small veins from the optic nerve

- Sometimes small veins from retina also join it

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Anterior Chamber

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Anterior Chamber

Bounded antly by cornea and postly by ant

surface of iris and part of ciliary body

About 3m deep in adults.

Shallow in young an old people.

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Anterior Chamber

Shallow in hyperopes.

Deep in myopes and aphakics.

Contains about 0.25ml of AH

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Angle structures

Ciliary body band

Scleral spur

Trabaecular meshwork

Schlemns canal.

Schwalbes line

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Ciliary body band

Most post landmark of the angle

Formed by ant most part of ciliary body.

Grey or dark brown

Wider in myopes.

Narrow in hyperopes Hiral Korani


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Scleral spur

Post portion of scleral sulcus

Usually white line on goniocopy

Attached at Ciliary body postly and corneo

Scleral meshwork

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Function is for drainage of AH.

Roughly triangular in shape.

Apex: Schwalbes line.

Base: scleral spur

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Divided into 3 parts:

- Uveal portion.

- Corneo scleral meshwork.

- Juxta canalicular tissue.

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Uveal portion and corneo scleral meshwork

divided by Schwalbes line to scleral spur..

Uveal portion Lies internal to this line.

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Pigmentation is variable.

Greater in brown iris than blue iris.

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Corneo scleral meshwork

Series of thin perforated connective tissue.

Arranged in lamellar pattern.

Extends from scleral spur to lateral wall of

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Uveal Trabaecular meshwork

Cord like, with fewer elastic fibrils.

Extends from iris root and CB to Schwalbe's

line

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Juxtacanalicular meshwork

Outer most portion of the TM.

Loosely arranged connective tissue lined on

either side by endothelium.

Part of it connects corneo scleral meshwork

with Schlemn's canal (large venous channel)

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Juxtacanalicular meshwork

Gives normal resistance to aqueous outflow.

Lined on either side by endothelium

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Schlemms canal

Lined by endothelium.

Contains numerous opening of collector

channels.

Help to keep canal open.

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Collector channel

Called intrascleral aqueous vessels.

Leave SC obliquely to terminate ultimately

into episcleral veins.

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Schwalbes line

Fine ridge in front of TM.

End of Descemets membrane.

Forms ant structure of angle.

Lies in post corneal surface.

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Embryology.


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Introduction

Three primary layers:

- Outer collagenous layer. (Sclera, cornea)

- Middle Vascular layer. (Uvea)

- Inner Sensory layer. ( retina , optic nerve)


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Introduction

Embryology is important to know:

- Structure and its anatomic characteristics.

- Diseases of the eye.

- Pathogenesis of various congenital anomalies


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Early development. (During and after 3rdweek)

Before 3rdweek : trilaminar str.

Consist of:

- Ectoderm.

- Mesoderm.

- Endoderm.


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Early development. (During and after 3rdweek)

Anterior Ectoderm cells proliferate and

thicken to from Neural plate.( curved line).

On either side of groove Ectoderm thickens

to form neural folds which meet to for

Neural tube.


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Early development (During and after 3rdweek)

At end of third week of gestation Neural tube

closes.

Formation of small depression called optic pit.

Optic pit enlarge to form Optic Vesicles.


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Early development. (During and after 3rdweek) Surrounding Optic vesicle is Mesoderm.

Helps in development of vascular system and

mesodermal str. of eye.

Proximal part of Optic vesicle forms Optic

stalk.


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Fourth week of gestation

Invaginaiton of Optic vesicle distally andinferiorly to form Optic cup.

Inferior invaginaiton to this optic vesicle formsembryonic fissure.

Extends from Peripheral rim of optic cup toLateral wall of Forebrain.


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Fourth week of gestation

Embryonic fissure helps in development of ON

and Vascular elements of an eye.

Complete closure of Fissure at 6thweek of

gestation.


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Sixth to seventh of gestation.

Incomplete closure of embryonic fissure leads

to coloboma or incomplete formation of an

eye str.

Complete closure of fissure is present most

structures are formed.


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Orbit

4thweek : Optic axes of two orbits are 1800

2ndmonth: 720

3rdmonth: 450


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Lens

Derived for surface ectoderm.

3rdweek of gestation.

Formation triggered by forward growth of

optic vesicle with surface ectoderm.


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Stages of lens development.

First:thickening of surface ectoderm at site of opticvesicle called as lens plate.

Second: cells of lens plate arc postly formingoutward concave depression called lens pit. By 22 to23 days of gestation.

Remaining surface ectoderm forms cornealepithelium


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Third: Lens vesicle entirely formed.

Fourth: lens vesicle consist of cuboidal

epithelium. Anterior cells do not increase in

length as in case of posterior cells to project

into lumen of vesicle.


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Fifth:Fibers grow till embryonic lens nucleus

completely formed by end of 4th week of

gestation.


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Lens

Lens capsule is thicker anteriorly than

posteriorly.

Formed by 5thweek of gestation.

Lens suture begins at 2ndmonth of gestation.


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Lens

Development of primary lens nucleus.

Fibers extend form ant to post pole.

Each time new fibers formation.

Finally formation of Y sutures.


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Lens

Linear junction where fibers terminate at ant

and post surface of lens forms Lens Sutures.

All fibers meet at single point leads to pit

formation leading to bad optical quality


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Lens

Later in gestation and following birthformation of these y sutures are irregular.

Progressive addition of lens fibersresults in appearance of Zones.

- Primary lens nucleus.

- Fetal Nucleus.- Infantile Nucleus.

- Adult Nucleus.

- Cortex.


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Retina

Sensory retina and RPE develop from two

layers of original Optic cup.

Ant rim of Optic cup: Epithelial layers of iris

and ciliary body.


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Retina

Distal part of Optic vesicle forming Sensory

retina divides into 2 Zones:

- Outer Zones: 8 -9 rows of Nuclei.

- Inner zone: Devoid of nuclei called marginal

zone.


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Retina

Five and half months of gestation all layers of

retina are developed.

Macula: 3rdmonth to 8thmonth of gestation.

Fovea: last several months after birth.


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Uvea

Stroma of 3 layers of Uvea are Mesodermallyderived.

Melanocytes: fifth month of gestation.

Iris:developd from 2 grem layers

- Ant stroma: Mesoderm

- Post pigment epithelium and sphincter:neuroectoderm.

S l


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Sclera

Originates around seventh week of gestation.

Starts a limbus progress until it reaches

posterior pole at fifth month.


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Crystalline lens

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I d i


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Introduction

Biconvex.

Located in posterior chamber.

Behind pupil.

Held in position by zonules.

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I d i


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Introduction

Transparent crystalline structure.

Power of about 20 D.

Avascular.

Posteriorly in contact with vitreous in circular areacalled Weigers ligament.

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I t d ti


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Introduction

Between the hyaloid face and lens capsulesmall cavity called retrolental space orBerger's space.

Its nourishment primarily by hyaloid arteryduring fetal life.

Later by aqueous and vitreous.

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I t d ti


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Introduction

Continuous to grow throughout life. Color changes with age.

Transparent : infants and young

Adults: colorless.

Definite yellow tinge : about 30 yrs or more.

Amber : old ageHiral Korani

Di


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Dimensons

At Birth:

EQ :

6.4mm

AP: 3.5

mm

WT: 90gm

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Di


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Dimensons

At Adult life.

EQ: 9-10mm.

AP: 5mm

WT: 255gm

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Oth t


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Other parameters

RI: 1.39

Anterior surface: 10mm

Posterior surface: 6mm.

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St t


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Structure

Three layers.

- lens capsule.

- Epithelium.

- Nucleus and cortex.

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C l


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Capsule

Thin transparent membrane.

Surrounds the lens.

Highly elastic.

Composed of type IV collagen fibers.

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Capsule


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Capsule

Anterior twice thicker than posterior.

Increases in thickness throughout.

Function : accommodation.

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Epithelium


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Epithelium

Single layer of cuboidal nucleated epithelialcells.

Beneath anterior and equatorial capsule.

Not present in post capsule

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Epithelium


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Epithelium

No attachment sites between lens epitheliumand basal lamina.

Cells undergo mitosis in pre equatorial zone.

Cell become elongated and descends to the

deeper layers.

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Epithelium


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Epithelium

Absence of division at post capsule, leavespost capsule clear.

Biosynthesis of DNA, RNA and Proteins takes

place.

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Lens substance or fibers


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Cortex and nuclear fibers derived frommigrating epithelial cells.

Cortical cells: hexagonal. Numerousinterlocking projections present.

Lens sutures : due to inter-digitation of apicalprocesses.

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Appear as erect Y which is seen ant surface ofnucleus and inverted Y in post nucleus.

Within this nucleus are different zones of diff

optical densities.which are laid down

throughout life.

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Embryonic nucleus: innermost part (1-3months of gestation).

Fetal nucleus: ( 3 months of gestation).

Infantile nucleus: ( birth to puberty)

Adult nucleus:( adult life)

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zonules


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zonules

Supports lens.

Originate from basal lamina of non-pigmented

layer of ciliary body.

Attach to ant lens capsule and post to equator.

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Zonules


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Zonules

Made up of multiple filaments of collagen .

Insert lens capsule

- 1.5 mm ant capsule.

- 1.25 mm post capsule.

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Zonules


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Zonules

Diameter of each Zonule: 0.35-1 microns.

Function in accommodation.

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Vitreous

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General Features


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General Features

Inert, transparent, colorless, jelly like,hydrophilic gel acts as supporting str to the

eyeball.

Occupies 4/5thof the volume of the globe.

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Location


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Location

Bounded Antly by lens and ciliary body andPostly by retina.

Adherence: 2mm ant and 4mm post to ora

serrata

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Attachments


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Attachments

Disc margin (outer rim area of Martigiane).

Perifoveal region.

Posterior lens capsule (hyaloidocapsular

ligament of Weiger)

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Composition


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Composition

Largest, simplest, single piece connectivetissue.

- H2O content: 99%

- Weight: 40 gms.

- Volume: 4ml

- Viscosity : twice of water

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Structure


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Structure

Divided into three parts

- hyaloid layer

- Cortical vitreous

- Medullary Vitreous

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Hyaloid Vitreous


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Hyaloid Vitreous

Not a true membrane.

Str of connective tissue.

Fibrils run parallel to the surface

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Ant hyaloid layer


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Ant hyaloid layer

Covers Antly. Approx.: 1.5mm from oraserrata.

Lies in contact with pars plana , ciliaryprocesses, ciliary zonules ,post lens capsule.

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Ant hyaloid layer


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Ant hyaloid layer

Firm adhered in younger individuals called asWeiger's Ligament.

Within this a potential space is called asBergers space or retrolental space.

Middle of Bergers space hyaloid turnsbackwards to form Cloquets canal

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Post hyaloid membrane


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Post hyaloid membrane

Extends back from the vitreous to optic disc.

In contact with ILM of retina.

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Cortical vitreous


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Cortical vitreous

Refers to entire peripheral vitreous.

Approx.100 microns in width.

Condensed fibrillar vitreous.

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Cortical vitreous


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Cortical vitreous

Consist of type II collagen fibrils.

Interspersed with sodium mucopolysaccharide

molecules.

Represents 2% of total vitreous.

Product of neuro-ectoderm.

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Cortical vitreous


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Cortical vitreous

Contain vitreous cells called Hyalocytes.

Found in cortical vitreous except in

retrolental part.

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Medullary vitreous


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Medullary vitreous

Forms vitreous body.

Similar to cortical vitreous.except for fibrils.

Centre to it is cloquets canal. Absent in

adults.

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Medullary vitreous


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Medullary vitreous

Represents remnants of hyaloid artery.

Mittendorf's dot represents remnants of the

ant end of hyaloid artery may be seen inadults.

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Embryology: 3 stages


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Iststage: 1stmonth of gestation: Space- lensand retina filled with primary vitreous.

IInd Stage: 2ndmonth of gestation: collagenlike fibrils and hyaluronic acid forms secondary

vitreous.represents adult vitreous.

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14thweek: secondary vitreous begins to fill thevitreous cavity, by 7thmonth entire cavity.

Remnants of primary vitreous:SShaped called

Cloquets canal.

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IIIrd Stage: tertiary or zonular fibrils develop.Remants of foetal vasculature seen in adults

called as Mittendorf's dot.

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Function


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Function

Occupying major volume of the globe.

To absorb and redistribute forces applied to

surrounding ocular tissue.

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RETINA

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Introduction


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Innermost ,delicate layer of the eye.

Post pole thickness: 0.56mm

At EQ: 0.18to 0.2mm.

At Ora Serrata:approx. 0.1mm

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Introduction


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Highly developed tissue.

Appears purplish red.

After death: white opaque.

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Gross Anatomy


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y

Extends from optic disc to ora serrata.

OPTIC DISC:

- pale disc. About 1.5 mm dia.

- All retinal layers terminate at optic disc.

- Except NFL (lamina Cribrosa).

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Gross Anatomy


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y

Macula:

- yellow spot.

- 5.5 mm dia.

- Temporal to optic disc.

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Gross Anatomy


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Gross Anatomy

Fovea: sensitive part

- depressed part of macula.

- 1.85 mm dia.

- Corresponds 50 of visualfield.

- Surrounding to it isparafoveal and perifovealareas.

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Gross Anatomy


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y

Foveola:

- central floor of fovea.

- 2 disc dia (3mm) away to temporal edge of

optic disc .

- 0.35 mm dia

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Gross Anatomy


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y

Umbo:

- tiny depression in centre of foveola.

- Corresponds as foveolar reflex during

ophthalmoscopy

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Gross Anatomy


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y

FAZ:

- located inside fovea but outside foveola

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Microscopic structures


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p

RPE.

Layers of rods and cones.

ELM.

ONL

OPL

INL

IPL

Ganglion layer

NFL

ILM

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Retinal pigment Epithelium


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Outermost layer.

Consist of hexagonal shaped cells

Firmly adherent to Bruchs membrane and loosely to

rods and cones.

Space between RPE and sensory retina : Subretinalspace

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RPE cells at fovea are taller and contain morepigment.

pigmentation is not equal ,gives granularappearance to retina.

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Function:

- photoreceptors renewal.

- Recycling of vit A.

- Integrity of subretinal space forming blood

retinal barrier

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Function:- transport of nutrients

- Phagocytic action.

- Support to photoreceptors.

- Absorption of light

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Layers of rods and cones


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Are photoreceptors.

Transform light energy

to visual energy.

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ROD:- Subserves peripheral

vision and helps in

scotopic vision.

- Absent at fovea in area

of 0.35mm which

corresponds to 1.250ofvisual field.

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ROD CELL:- about 4060 micron

long.

- Outer segment is

cylindrical.

- Contain visual purple.

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ROD CELL:- contain proteins lamellar

disc.

- Disc contains 90% visualpigment.

- Inner segment:thicker.Contains mitochondria Golgi

bodies, usual organelles

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ROD CELL:

- outer rod fiber layer: arise

from inner end of rod,

passes through ELM and

then terminates as innerrod fiber which lies in OPL,

which end at rod spherules

in contact with cone foot.

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CONE:- helps in photopic vision

and for color vision.

- About 6.5 million cones.

- More at fovea

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Cones:- about 4080 microns long

- Largest at fovea andshortest at periphery.

- Cone outer segment:conical, shorter than rod,contains iodopsin, disc

smaller than rod

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Cones :

- cone inner segment:

similar to the rod.

- Inner segment: directly

continuous with the

nucleus and lies in ONL.

And ends at cone footwhich lies at OPL

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External Limiting Membrane


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Is not a true basement membrane.

Extends form ora serrata to edge of optic

disc.

Is formed by junctions between

photoreceptors and mullers cells

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Outer nuclear layer


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Formed by nuclei ofrods and cones.

Cone nuclei larger than

rod.

Lies in single layer next

to ELM.

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Outer plexiform layer


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Contains synapses betweenrod spherules and cone

pedicles with dendrites of

Bipolar cells

Thickest at the macula.

Also known as Henle's layer.

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Inner Nuclear layer


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Resembles outer nuclearlayer .

It is thin.

Consist of

- bipolar cells (INL)

- Horizontal cells( OPL)

- Amacrine cells (within OPL)

- Mullers cell (within INL)Hiral Korani

Inner plexiform layer


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Absent at foveola.

Consist of synapses

between axons of

bipolar cells(1st order

neurons), dendrites of

ganglion cells (2ndorder

neurons) and process ofamacrine cells

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Ganglion cell layer


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Throughout of the retina this layer is of singlelayer except at macula which is multi layered.

Absent at region of fovea.

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Nerve fiber layer


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Consist of unmyelinated axons of the ganglioncells.

Vessels lies in this layer

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Internal limiting membrane


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Consist of PAS +ve true Basement membrane.

Interface between retina and vitreous.

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Blood supply


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Outer four layers:from RPE to ONL bychoriocapillaries.

Six inner layers: from OPL to ILM by centralretinal artery.

OPL supplied partly by CRA andchoriocapillaries

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Blood supply


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Fovea an avascular zone supplied bychoriocapillaries.

Macula by CRA and cilioretinal artery

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Extra Ocular Muscles

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EOM


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For eye movements

4: rectii ( SR, MR, IR, LR)

2 oblique: (SO, IO)

1 levator palpebral superiors.

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All except IO originates at orbital apex.

4 rectii from: annulus of Zinn.

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Annulus of Zinn


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Is a fibrous ring.

Common origin of rectus muscles.

Orbital apex surrounded by annulus of Zinn called

occulomotor foramen.

Serves opening for CN III, IV, V, VI.

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Spiral of Tiallux


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Action of a muscle in primary

position


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Eye directed in straight head position.

Primary action: Muscle contracts when eye is

in primary Position.

Subsidiary action: Additional effects in

primary position

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Horizontal rectus muscles


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Medial Rectus:

- Action : Adduction.

- Origination: Annulus of Zinn.

Lateral Rectus:

- Action: Abduction.

- Origination: Annulus of Zinn

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Vertical Rectus Muscle


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Superior Rectus Muscle:

Origination: Annulus of

Zinn.

Course: anteriorly

upwards and laterally

forming 230 with Visualaxis

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Vertical Rectus Muscle


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-Action:

Primary: Elevation when

Abducted 230.

Muscle Axis & optic axis

coincide.

Secondary &Tertiary:

Intorsion when adducted

670 Hiral Korani

Vertical Rectus muscle


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Inferior Rectus:

Origination: Annulus of

Zinn.

Course: Anteriorly

Downwards and laterally

forming 230 With VisualAxis

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Inferior Rectus Muscle


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Action:

Primary action: Depression

when globe abducted 230

Secondary and tertiary

Action: Extorsion when

Adducted 670

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Oblique Muscle


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Superior Oblique:

Origination: orbital Apex

above Annulus of Zinn.

Course:Medially upwards

towards Trochlea.

Thereafter runs postlybelow SR form an angle of

510 Hiral Korani

Superior Oblique


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Action:

Primary Action: Intorsionwhen globe abducted 390

Optical axis and Pulley ofSO make 900 Angle.


Action: Depression whenAdducted 510 Muscle axisand Optical axis Coincide Hiral Korani

Inferior Oblique


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Origination: fromMaxillary Bone posterior to

Orbital rim and lateral to

the orifice to Lacrimal

Fossa.

Course : passes laterally

,Superior and posteriorlygoing inferior to inferior

rectus forming an angle of

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Inferior Oblique


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Action:Primary action: extorsion

when globe abducted

390


action: elevation when

globe adducted 510

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Blood supply


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Medial Rectus:Inferior muscular branch ofophthalmic artery.

Inferior Rectus: Inferior muscular branch ofophthalmic artery and infraorbital artery.

Lateral Rectus: Lacrimal artery.

Blood supply ctd..


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Superior Rectus: superior muscular branch ofophthalmic artery.

Superior Oblique: superior muscular branch of

ophthalmic artery

Inferior Oblique: Inferior muscular branch of

ophthalmic artery and infraorbital artery.

Definitions


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Muscle Cone: lies post to equator of EOM,

EOM sheath, Intermuscular membrane extends

postly to annulus of Zinn.

Muscle Capsule: extend form its origin to its

insertion. Near equator they thicken.

Definitions


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Check ligaments: limit excursion of EOM. Actas support structure to globe. Neither check

movements nor they are ligaments.

Inter muscular membrane: connects all rectii

with thin layer of tissue that underlies

conjunctiva

anat iind internal 2nd semester

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