ANATOMY OF UVEA

MODERATOR- DR. H.N. HAZARIKA PRESENTER- DR BARUN GARG

INTRODUCTION

• UVEA constitutes- middle vascular coat • 3 parts- a)iris b)ciliary body c)choroid

• Developmentally,structurally and functionally- indivisible

• color varies from light blue to dark brown

EMBRYOLOGY

IRIS- • Both layers of epithelium derived from

marginal region of optic cup (neuroectoderm)• Sphincter and dilator pupillae- anterior

epithelium (neuroectoderm)• Stroma and vessels- vascular mesoderm

CILIARY BODY• Both Epithelium from neuroectoderm• Ciliary processes from ciliary epithelium• Stroma and blood vessels – mesoderm

MILESTONES• 9TH WEEK GESTATION- ciliary body appears• 12TH WEEK GESTATION- sphincter pupillae

appears• 5TH MONTH- all layers of choroid seen - iris fully developed• 6TH MONTH- dilator muscle begins to form,

sphincter muscle is fully formed• POSTNATAL PERIOD- dilator muscle fully formed

by 5 years, iris stromal pigment develops after birth

IRIS

• Anterior most part• Avg diameter- 12mm, thickness- 0.5mm• In centre an aperture of 3-4mm- PUPIL• Thinnest at its root- tears away easily on blunt

trauma- IRIDODIALYSIS• Divides space into anterior and posterior

chamber

MACROSCOPIC APPEARANCE

TWO SURFACES

A)ANTERIOR SURFACE• Collarette- zigzag line, 2mm from pupil, thickest, represents attachment of

pupillary membrane• Divides surface into-a) CILIARY ZONE- c/b Radial streaks Crypts- peripheral-near the iris central- near collarette Contraction furrows- faints lines outside collaretteb) PUPILLARY ZONE- Between collarette and pigmented frill Pigmented frill- black pigment at pupillary margin -represents ant end of optic cup

B)POSTERIOR SURFACE- dark brown/black Contains-A) Schwalbe’s contraction folds- 1 mm from

pupillary border, little radial furrowsB) Schwalbe’s structural furrows- 1.5 mm from

pupillary borderC) Circular furrows- finer then radial furrows

MICROSCOPIC STRUCTURE FOUR LAYERS-a)Anterior limiting layer- consists melanocytes and fibroblasts Previously called endothelial layer• Colour of iris depends on this layer• Blue iris- thin layer and few pigment cells• Brown iris- thick and doubly pigmented

b) Iris stroma- • Forms main bulk• Consists of collagenous tissue with mucopolysaccharide• Structures embedded-

Sphincter pupillae- 1 mm broad circular band in pupillary area derived by ectoderm supplied by parasympathetic fibres by 3rd nerve

constricts pupil

Dilator pupillae- lies in posterior part of ciliary zone supplied by cervical sympathetics dilates pupil vessels- form bulk of stroma radial vessels- branches of circulous arteriosis major peculiarities- absence of IEL & non fenestrated capillary endothelium Pigment cells- melanocytes Lymphocytes, fibroblast and macrophages

C) Anterior epithelial layer anterior continuation of pigment epithelium of retina and ciliary body Lacks melanocytes Basal processes- give rise to dilator pupillae

D)Posterior pigmented epithelial layer Anterior continuation of non pigmented epithelium of ciliary body Derived from internal layer of optic cup Forms pigmented frill

FUNCTIONS OF IRIS

• CONTROLS AMOUNT OF LIGHT ENTERING THE EYE THROUGH PUPIL

• DEFINES EYE COLOUR• CONTROL DEPTH OF FIELD• SOURCE OF BLOOD OCULAR TISSUES

CILIARY BODY• Forward continuation of choroid at ora serrata• Triangular in cut section, ant side of its form part of angle , in

middle attached to iris and outer part lies against sclera• Triangle – two partsa) Anterior part- ciliary processes (pars plicata) 2-2.5mmb)Posterior part- smooth (pars plana) 5mm wide temporally & 3mm

nasally

MICROSCOPIC STRUCTURE1.SUPRACILIARY LAMINA- outermost part Consist of pigmented collagen fibres Posteriorly continuation of suprachoroidal lamina, ant continous

with anterior limiting membrane

2.STROMA- Consists Ciliary muscle- non striated, triangular in cut section, 3

parts Longitudnal/meridional fibres- origin from scleral spur,

inserts into suprachoroidal lamina Circular fibres- in inner portion, nearest to lens Radial fibres- obliquely placed Actions - slacken suspensory ligament thus helps in

accomodation circular fibres- directly as sphincter nerve supply- parasym. fibres from ciliary ganglion

Vascular stroma- major arterial circle liesFormed by anastomosis of long and short PCASupplies iris and ciliary body3)Layer of pigmented epithelium- forward continuation

of RPEAnteriorly continues to pigmented epithelium of iris4)Layer of non pigmented epithelium- forward

continuation of sensory retinaContinues anteriorly with pigmented epithelium of

iris5)Internal limiting membrane-lines NPEFrwd continuation of internal limiting membrane of

retina

CILIARY PROCESSES• Finger like projections from pars plicata• 70-80 in number, 2mm long 0.5mm diameter• Site of aqueous productionULTRASTRUCTURE1)Network of capillaries- in the centre• Has endothelium with fenestrae2)Stroma of ciliary processes- thin, separates

capillaries from epithelium3)Epithelium-two layered with apical apposition

FUNCTIONS OF CILIARY BODY

• Site of aqueous humour production• Maintenance of IOP• Constitutes blood aqueous barrier• Accommodation• Eicosanoids are synthesised in ciliary body

CHOROID

• Posterior most part• Extension- optic disc to ora serrata• Inner surface- smooth, brown and in contact

with RPE• Outer surface-rough and in contact with sclera• Thickness- posteriorly 0.22mm anteriorly 0.10mm

MICROSCOPIC STRUCTURE

1) Suprachoroidal lamina- lamina fusca• Thin layer, continues anteriorly with supraciliary lamina of ciliary body• Suprachoroidal space- contains long and short posterior ciliary arteries

and nerves

2) Stroma – plenty of pigmented cells, macrophages,mast and plasma cells• Vessels- form the bulk• Arranged in two layers- outer consisting of large vessels(hallers layer) ,

inner of medium vessels ( sattlers layer)

3) choriocapillaris- rich capillary network• Supplies pigment epithelium and outer layers of sensory retina• Few anastomosis with CRA

4)Basal lamina- bruch’s membrane/lamina vitrae

• Innermost layer• Between choriocapillaris and RPE• Electron microscopy- basement membrane of

RPE, inner collagen, middle elastic and outer collagen and basement membrane choriocapillaris

• With increasing age- produces hyaline excresences known as druscens

FUNCTIONS OF CHOROID

• BLOOD SUPPLY TO OUTER FOUR LAYERS OF RETINA

• MODULATION OF VASCULARISATION• REGULATE RETINAL HEAT• ASSIST IN THE CONTROL OF INTRAOCULAR

PRESSURE • PIGMENT ABSORBS EXCESS LIGHT SO

AVOIDING REFLECTION

BLOOD SUPPLY UVEAL TRACT1.SHORT POSTERIOR CILIARY ARTERIES• Branches of ophthalmic artery• Divides into 10-20 branches, pierce sclera around optic nerve• Supply choroid in segmental manner2) LONG POSTERIOR CILIARY ARTERIES• Two in number- nasal and temporal• Pierce sclera• Anastomose with anterior ciliary arteries- form major arterial circle supply

ciliary body3)ANTERIOR CILIARY ARTERIES• From muscular arteries• 7 in number• 2 each SR,IR,MR and 1 from LR• Anastomse with LPCA• Circulous arterious major and minor

VENOUS DRAINAGE

1)Anterior ciliary veins- tributaries of muscular veins

2)Smaller veins from sclera- carry blood only from sclera and not from choroid

3)Vena verticosae- 4 in no.Drain whole of choroid

UVEITIS• Inflammation of uveal tract• Usually U/L• CLASSIFICATION-A)ANATOMICAL1. ANTERIOR- iritis, iridocyclitis2. INTERMEDIATE- cyclitis, pars planitis3. POSTERIOR- retinitis, chorioretinits4. PANUVEITISB)PATHOLOGICAL5. GRANULOMATOUS6. NON GARNULOMATOUS

CONGENITAL ANOMALIES1.HETEROCHROMIA-• Iridum• Iridis2.POLYCORIA- more then one pupil3.CORECTOPIA- abnormally eccentric pupil

4. ANIRIDIA- abscence of iris• o/e- a narrow rim of iris tissue behind sclera seen

oftenly• zonules of lens and ciliary processes often visible5. PERSISTENT PUPILLARY MEMBRANE-• Persistent part of ant vascular sheath of lens• Attached to collarate

5.COLOBOMA UVEA- defect in tissue• incomplete closure of the embryonic fissure during

development• Associations- micropthalmia, cataract, glaucoma, refractive

error, CHARGE syndrome, colobomas of lids/lens/retina• Mutation PAX2 gene• Types –• a) typical – inferonasal quadrant, pupil is pear shaped Choroidal coloboma- oval, rounded apex towards disc,

vessels traversing disc, disc may be involved b)atypical- elsewhere, iris involved etiology- intrauterine inflammations and fibrovascular sheath persistence

CYST OF IRIS- congenital cyst may arise from a)stroma- derived from ectopic cells of surface ectoderm of developing lens

b)pigment epithelium- due to failure of fusion of two layers of optic vesicle

Axenfeld anomaly Rieger anomaly

Peter's anomaly Sclerocornea

Abnormal neural crest cell migration

Abnormal neural crest cell proliferation

Iridocorneal Endothelial Syndrome

Progressive iris atrophy

Iris naevus (Cogan-Reese) syndrome

Chandler syndrome

BRUSHFIELD SPOTS IN DOWNS SYNDROME

LISCH NODULES IN NF1