GROSS ANATOMY OFTHE EYE

•Cystic structure kept distended by the pressure inside it•Shape-oblate spheroid•Anterior and posterior poles•Equator•Dimensions AP-24mm Horizontal-23.5mm Vertical diameter-23mm Circumference-75mm Vol-6.5ml Weight-7g

SEGMENTS AND CHAMBERS

Anterior segment-crystalline lens, iris, cornea, anterior and

posterior chambers-Anterior chamber: 2.5mm deep in the center anteriorly-cornea postriorly-iris and part of ciliary body aqueous humour-0.25ml

-Posterior chamber triangular space anteriorly-iris and part of ciliary body posteriorly-lens and zonules laterally-ciliary body aqueous humour-0.06ml Posterior segment-structures posterior to the lens

THE ORBIT

Quadrilateral truncated pyramid shaped cavity

Location -above: anterior cranial fossa -below: maxillary sinuses 40 mm in height,width and depth Formed by 6 bones-Frontal,Maxilla,Zygomatic

bone,Sphenoid,Palatine,Ethmoid,Lacrimal

4 walls-superior,inferior,medial,lateral Base Apex 2 orifices -optic canal :optic nerve & ophthalmic artery - superior orbital fissure:nerves,arteries,veins

ORBITAL FASCIA Thin connective tissue membrane lining

various intra orbital structures Divided into Fascia bulbi or Tenons capsule Muscular sheath Intermuscular septa Membraneous expansions of extraocular

muscles Ligament of Lockwood

EYELIDS

In front of the eyeball Function as -shutters - spreads tear film -helps in drainage of tears Parts of the eyelid-orbital and tarsal parts Position of eyelids Canthi- at the medial and lateral angles(inner

and outer canthi)

Palpebral aperture Vertical-10-11mm Horizontal-28-30mm Lid margin -2mm broad -medial or lacrimal portion -lateral or ciliary portion -intersegmental strip-grey line-junction of skin and conjunctiva

STRUCTURE

1.Skin: elastic2.Subcutaneous areolar tissue: loose and

contains no fat3.Layer of striated muscle: orbicularis muscle which comprises of three

portions-orbital,palpebral and lacrimal Levator palpebrae superioiris

4.Submuscular areolar tissue: loose connective tissue with nerves ans vessels

5.Fibrous layer -tarsal plate: two plates of dense connective tissue shape and firmness to the eyelids Joins at the medial and lateral canthi Attached to the orbital margin by the medial and

lateral palbebral ligaments Contains Meibomian glands

-septum orbitale Thin membrane of connective tissue Attachments central-tarsal plates peripheral-periosteun of orbital margin Perforated by nerves muscles and LPS

6.Layer of non striated muscle fiberPalpebral muscle of MullerUpper lid-fibers of LPSLower lid-Prolongation of inferiorrectus muscle7.Conjunctiva-palpebral conjunctiva

CONJUNCTIVA

Translucent mucous membrane Lines posterior surface of eyelid and anterior

surface of eyeball Extends between the lid margin and the

limbus Encloses the conjunctival sac

PARTS OF THE CONJUNCTIVA

i. Palpebral conjunctiva-lines the eyelids a-Marginal conjunctiva - extension:from the lid margin for 2mm on

the back of the eyelid upto sulcus subtarsalis

-transitional zoneB-Tarsal conjunctiva -thin,transparent and highly vascular -upper eyelid: entire plate -lower eyelid: half the width of the tarsus

c-Orbital part -between the tarsal plate and fornixii. Bulbar conjunctiva-thin,transparent -can be moved easily -Tenons capsule and episcleral tissue seperates it

from anterior sclera -limbal conjunctiva-Tenons capsule+episcleral

tissue+bulbar conjunctiva

iii.Conjunctival fornix- circular cul de sac broken medially Joins bulbar and palpebral conjunctiva Subdivided-superior,inferior,medial and lateral

Plica semilunaris:-pinkish cresentic fold of conjunctiva in the medial

canthusCaruncle-small pinkish fold of skin in the inner canthus

medial to plica semilunaris

GLANDS OF CONJUNCTIVA

1. Mucin secretory glands-goblet cells-crypts of Henle-glands of Manz2. Accessory lacrimal glands-glands of Krause-glands of Wolfring

COATS OF THE EYEBALL

Fibrous coat:dense strong coati. Cornea -transparent,avascular structure -anterior 1/6 th of the fibrous coat of the

eyeball -anterior surface-elliptical -horizontal-11.7mm -vertical-11mm -posterior suface-circular - average diameter-

11.5mm

-thickness: center-0.5-0.6 mm periphery-1-1.2mm -radius of curvature anterior- 7.8mm posterior-6.5 mm -refractive index-1.376 -refractive power-45 Dii. Sclera -posterior 5/6 opaque part - covered by Tenons capsule and conjunctiva -related to choroid and suprachoroidal space

- thickest posteriorly and thin anteriorly -thinnest-insertion of extraocular muscles-lamina cribrosa-Apertures: Posterior aperture around optic nerve transmits ciliary nerves and vessels Middle apertures posterior to equator transmits four vortex viens Anterior aperture 3-4mm from the limbus transmits anterior ciliary vessels and long

ciliary nerves

Middle vascular coat - iris,ciliary body,choroid i. Iris anterior most part Circular disc shaped Pupil-aperture of 4mm diameter at the centre Forms anterior and posterior chambers Attached to the middle of the anterior surface of

ciliary body Anterior surface of eyelids Ciliary zone Pupillary zone

ii. Ciliary body-Forward continuation of choroid at ora serrata-Triangular in cross section-Iris is attached to the middle-Supraciliary space-Inner side-anteriorly pars plicata and posteriorly pars

planaiii. Choroid-posterior most part-from optic disc to ora serrata-inner surface: smooth, brown and in contact with

pigment epithellium of retina-outer surface:rough and in contact with sclera

RETINA

Thin,delicate and transparent Extends from optic disc to ora serrata Retinal equator-imaginary line considered to

lie in line with the exit of four vena verticose veins. Seperates it into

A. Posterior pole-posterior to retinal equator i. optic disc central area-all the retinal layers

terminate except nerve fibres physiological cup

ii. Macula lutea-yellow spot Fovea centralis FoveolaB. Peripheral retina posteriorly-retinal equator anteriorly- ora serrata

Ora serrata Serrated margin Retina is attached to vitreous and choroid Pars plana extends from it

LENS

Transparent,biconvex,crystalline structure Located between the iris and vitreous humor Patellar fossa-saucer shaped depression Diameter-9-10mm Thickness 3.5-5mm Two surfaces-anterior and posterior RI-1.39 Total dioptric power-18D(16-20D)

STRUCTURE

1. Lens capsule Thin, transparent hyaline membrane Thicker anteriorly Thickest at pre equatorial regions Thinnest at the posterior pole2. Anterior epithellium Single layer of cuboidal epithellial cells Columnar at the equatorial region Form new lens fibres No posterior epithellium

3. LENS FIBRESNUCLEUS AND CORTEX

4. Suspensory ligaments of lens Set of fibres passing from ciliary body to lens Holds the lens in position Ciliary muscles act on it 3 groups-anterior group -middle group -posterior group

EXTRAOCULAR MUSCLES

Rectus muscles Superior,medial,lateral,inferior Origin: Arises from Annulus of Zinn- attached

to the apex of the orbit surrounding the optic foramina and medial part of superior orbital fissure

Insertion: sclera by flat tendons at different distances from the limbus

Medial-5.5mmInferior -6.5mmLateral-6.9mmSuperior-7.7mm Oblique muscles Superior oblique muscle-origin: sphenoid by a narrow tendon above and medial to optic foramen-insertion: passes through the trochlea :upper and outer part of sclera :behind the equator

Inferior oblique muscle-origin: orbital plate of maxilla :lateral to orifice of nasolacrimal duct-insertion: lower and outer part of sclera : behind the equator

LACRIMAL GLAND