The Eyeball Auto Saved)

8/2/2019 The Eyeball Auto Saved)

1/61

By:

Amir MadadiDDM-1

The Eyeball


2/61

Eyeball

- organ of sight- spherical in shape

- diameter is about 2.5cm

-made up of three concentric coats

*fibrous coat comprises sclera & cornea

*vascular coat - middle part

- also called uveal tract

- consists of the choroid, ciliary body, and the iris

*nervous coat inner part, is the retina


3/61

OUTER

COAT SCLERA

CORNEA


4/61

SCLERAO sklera = hardO opaque and forms the posterior five-sixths of the

eyeball

O composed ofdense fibrous tissue w/c is firm andmaintains the shape of the eyeball

O thickest behind, near the entrance of the optic nerveand the thinnest about 6mm behind the sclerocornealjucntion where the recti muscles are inserted

O weakest at the entrance of the optic nerve

*lamina cribrosa seive-like apperance region; numerousperforations for passage of the fibers of the optic nerve


5/61


6/61

SCLERA

Inner surface

O brown and grooved for the ciliary nerves and vessels

O separated from the choroid by theperichoroidal spacewhich contains a delicate cellular tissue, termed the

suprachoroidal lamina or lamina fusca of the sclera


7/61


8/61

Lens


9/61

SCLERA

O fused posteriorly with the dura sheath of the optic nerve

O provides insertion to the extrinsic muscles of the eyeball

**Extrinsic muscles :- Recti in front of the equator

- Oblique muscles behind the equator


10/61

SCLERA

O pierced by a number of structures:

a. Optic nerve pierces it a little inferomedial to the posterior

pole of the eyeballb. Ciliary nerves and arteries pierces it around the entrance

of the optic nerve

c. Anterior ciliary nerves pierce it near the limbus

d. Four venae vorticosae or the choroid veins pass out through

the sclera just behind the equator


11/61

SCLERA

O almost avascular

*episclera loose connective tissue between the

conjunctiva and sclera that is vascular


12/61

CORNEA

O transparent

O replaces the sclera over the anterior one sixth of theeyeball

*Sclerocorneal junction or limbus its junction withthe sclera

- more convex than the sclera, but the curvaturediminishes with age

- separated from the iris by a space called theanterior chamber of the eye


13/61

CORNEA

O avascular

O nourished by lymph which circulates in the numerous

corneal spacesO supplied by branches of the ophthalmic nerve

(through the ciliary ganglion) and the short ciliary

nerves

*Pain is the only sensation aroused from the cornea


14/61

CORNEA

O structurally, consists of layers from before backwards:

a. Corneal epithelium stratified squamous nonkeratinizedtype

- continuous with that of the conjunctiva

b. Bowmans membrane anterior elastic lamina

- structureless homogenous layer

c. Substantia propria consists of bundles of dense collagenfibers separated by corneal spaces


15/61

CORNEA

d. Descemets membrane or posterior elastic lamina

- also structureless and homogenous butcontains elastic fibers

-at the peripheral margin its fibers divided into3 groups

*Inner fibers turn medially on to the iris andconstitute the ligamentum pectinatum

*Middlefibers give origin to the ciliary muscles

*Outer fibers are continuous with the sclera


16/61

CORNEA

e. Simple squamous mesothelium lines the posterior

surface of the cornea


17/61


18/61

MIDDLE COAT CHOROID

CILIARY BODY

IRIS


19/61

CHOROID

O thin pigmented layer which separates the posterior

part of the sclera of the retina

O anteriorly, it ends at the ora serrata by merging withthe ciliary body

O posteriorly, perforated by the optic nerve to which it

is firmly attached


20/61

*Outer surface: is separated from the sclera by the

suprachoroidal lamina which is traversed by the

ciliary vessels and nerves

- loose attachment to the sclera, so it is easily

stripped

*Innes surface: firmly united to the retina

CHOROID


21/61

*Structurally, consists of:

a. Suprachoroidal lamina made of collagen fibers, elasticfibers and pigment cells

b. Vascular lamina composed of arteries and short posterior

ciliary veins, the latter being arranged in the form of whorlswhich converge to form 4 to 5 venae vorticosae, loose areolartissue and pigment cells

c. Choriocapillary lamina forms the most prominent feature ofthe choroid

- nourishes the rods and cones of the retina by diffusiond. Membrane of Bruch inner basal lamina or lamina vitrea

- thin structureless transparent membrane which is firmlyadherent to the outer, pigmented layer of the retina

CHOROID


22/61


23/61

O thickened part of the uveal tract lying just posterior

to the corneal limbus

O continuous anteriorlywith the iris, andposteriorlywith the choroid

O suspends the lens and helps in accommodation for

near vision

CILIARY BODY


24/61

CILIARY BODY

1. Ciliary body

O triangular in cross-section

O Thick in front & thin behind

O Scleral surface of this body contains ciliary muscles

*PARS PLANA

O Smooth & black posterior part of the vitreous surface

*PARS PLICATA

O Ridged anteriorly to form about 70 ciliary processes atthe anterior part


25/61

CILIARY BODY

2. Ciliary zonule

- thickened vitreous membrane fitted to

the posterior surfaces of the ciliary processes- posterior layerlines hyaloid fossa

- anterior thick layerforms the suspensory

ligament of the lens


26/61

CILIARY BODY

3. Ciliary muscle

- ring of unstripped muscle which are longitudinal ormeridional, radial and circular

*Longitudinal or meridional fibers

- arise from a projection of sclera or scleral spur near thelimbus

- radiate backwards to the suprachoroidal lamina

*Radial fibers

- obliquely placed and get continuous with the circular fibers

*Circular fibers

- lie within the anterior part of the ciliary body & are nearestto the lens

**all parts of the muscle are supplied by parasympathetic nerves

**pathway involves the Edinger-Westphal nucleus, oculomotor nerve &ciliary ganglion


27/61


28/61

IRISO Anterior part of the uveal tract

O Forms a circular curtain with an opening in the center,

called the Pupil

O By adjusting the size of the pupil it controls the amount

of light entering the eye


29/61

IRISO Placed vertically between the cornea and the lens,

thus divides the anterior segment of the eye intoanterior & posterior chambers, both containing

aqueous humourO Peripheral margin

O attached to the middle of the anterior surface of theciliary body

O Separated from the cornea by the iridocorneal angle or

angle of the anterior chamberO Central free margin

O Forming the boundary of the pupil rests against the lens


30/61

IRISO Anterior surface of the iris: covered by a single layer of

mesothelium

O Posterior surface: double layer of deeply pigmented cellswhich are continuous with those of the ciliary body

O Main bulk of the iris: formed by the stroma made up of bloodvessels and loose connective tissue in which there arepigmented cells

*Major arterial surface joined long posterior & anterior ciliarynerves at the periphery of the iris

* Minor arterial surface joined arterial circle vessels thatconverge towards the free margin of the iris


31/61

IRISO Its color: determined by the number of pigmented

cells in its connective tissue

*if pigment cells are absent, the iris is blue in color due

to the diffusion of light in front of the black posterior

surface


32/61

IRISO Contains a well-developed ring of muscle called

sphincter pupillae which lies near the margin of the

pupil

O Dilator pupillae

O Ill-defined sheet of radial muscle fibers placed near the

posterior surface of the iris


33/61


34/61

INNER COAT

RETINA


35/61

RETINAO Thin, delicate inner layer of the eyeball

O Continuous posteriorly with the optic nerve

O

Outer surface: attached to the choroidO Inner surface: in contact with the hyaloid membrane (of

the vitreous)

*Optic disc

O Circular area opposite the entrance of the optic nerve

inferomedial to the posterior pole

O 1.5mm in diameter


36/61

RETINAO Diminishes in thickness from behind forwards

O Divided into optic, ciliary & iridial parts

*Optic partO Contains nervous tissue & is sensitive to light

O Extends from the optic disc to the posterior end of the

ciliary body

*Ora serrata

O Wavy line at the anterior margin of the optic part of the

retina


37/61

RETINA*Ciliary & Iridial parts

O thin, non-nervous insensitive layer that covers the ciliary

body and the iris, continued forwards beyond the ora

serrata

O Made up of two layers of epithelial cells


38/61

*Physiological cup

O Depressed area of the optic disc

O Contains no rods or cones and is therefore insensitive tolight

O It is thephysiological blind spot

*Macula Lutea

O Depression at the posterior pole of the eye 3mm lateral to the

optic disc

O Avascular & yellow in color

*Fovea Centralis

O Further depression at the center of the macula

O Thinnest part of the retina

O Contains cones only

O Site of maximum acuity of vision


39/61


40/61

Macula and Fovea centralis

Optic Disc


41/61

RETINA-rods & cones are the light receptors of the eye*Rods

O Contain a pigment called Visual purple

O Respond to dim light (scotopic vision)

O Only at the periphery of the retina

*Cones

O Respond to bright light (Photopic vision)

O Sensitive to color

O Only at fovea centralis

O Number diminishes towards the periphery of the retina


42/61

RETINAO Composed of ten layers:

1. Outer pigmented layer

2. Layer of rods & cones

3. External limiting membrane4. Outer nuclear layer

5. Outer plexiform layer

6. Inner nuclear layer (bipolar cells)

7. Inner plexiform layer

8. Ganglion cell layer

9. Nerve fiber layer

10. Internal limiting membrane


43/61

RETINAO Supplied by the central artery(an end artery)

O In the optic disc, it divides into an upper & lower branch,

each giving off nasal & temporal branches

O Supplies the deeper layers of the retina up to the bipolarcells

*rods & cones : supplied by diffusion from the capillaries

of the choroid

*retinal veins run with the arteries


44/61


45/61

AQUEOUS HUMOUR


46/61

Aqueous HumourO Clear fluid which fills the space between the

cornea in front & the lens behind the anterior

segment

O Divided by iris into anterior & posterior

chambers which freely communicate which

freely communicate with each other through

the pupil


47/61

Aqueous HumourO Secreted into the posterior chamber from the

capillaries in the ciliary processes

O

Passes into the anterior chamber through thepupil

O From anterior chamber, it is draines into the

anterior ciliary veins through the spaces of the

iridocorneal angle or angle of anterior

chamber & the canal of Schlemm


48/61

Aqueous HumourO Glaucoma

O Increase of intraocular pressure due tointerference with the drainage of the aqueous

humour into the canal of SchlemmO Produces cupping of the optic disc and

pressure atrophy of the retina causingblindness

*intraocular pressure is due chiefly to the

aqueous humour which maintains the constancyof the optical dimensions of the eyeball


49/61

Aqueous HumourO Rich in ascorbic acid, glucose & amino acids

O Nourishes the avascular tissues of the cornea

& lens


50/61


51/61

the LENS


52/61

The LensO Transparent biconvex structure

O Placed between the anterior & posterior

segments of the eye

O Circular in outline & has a diameter of 1cm

**Anterior and Posterior poles

O Central points of the anterior & posteriorsurfaces


53/61

The LensO Axis of the lens

O Line connecting the poles

O EquatorO Marginal circumference

O Posterior surface of the lens is more convex than theanterior

O Anterior surface kept flattened by the tension of thesuspensory ligament

*When the ligament is relaxed by contraction of the ciliarymuscle, the anterior surface becomes more convex due toelasticity of the lens substance


54/61

The Lens

O Enclosed in a transparent, structureless,elastic capsule which is thickened anteriorlynear the circumference

O Capsular epitheliumO Covers the anterior surface of the lens, deep to

capsule

O Made up of a single layer of cuboidal cells, atthe center of the anterior surface

O Cells elongate to produce fibers of the lens, atthe periphery


55/61

The Lens

O Fibers are concentrically arranged to form the

lens substance

O Center of the lens

O Firm & consists of the oldest fibers

O Periphery or cortex of the lens

O Soft & made up of more recently formed fibers


56/61

The Lens

O Suspensory Ligament of the Lens or the

Zonule of Zinn

O Retains the lens in position & its tension keeps

the anterior surface of the lens flattened

O Made up of a series of fibers which are

attached peripherally to the ciliary processes,

to the furrows between ciliry processes and to

the ora serrata


57/61


58/61

VITREOUS BODY


59/61

Vitreous Body

O Colorless, jellylike transparent mass

O Fills the posterior segment (posterior 4/5) of the

eyeball

O Enclosed in a delicate homogenous hyaloid

membrane

O Behind: attached to the optic disc

O Front: Ora serrata

O Between: free & lies in contact with the retinaO Anterior surface: indented by the lens & ciliary processes


60/61


61/61

Documents

The Eyeball Auto Saved)