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Anatomy of uvea
The uvea consists of the iris, ciliary body, and choroid. It develops from both neuroectoderm and mesoderm. The iris controls the pupil size and appears by 9 weeks gestation. The ciliary body produces aqueous humor and appears by 9 weeks. The choroid supplies the outer retina and appears by 5 months gestation. The uvea contains muscles, epithelia, and vasculature. It is susceptible to inflammation and various congenital anomalies that can affect its structure and function.
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Anatomy of uvea
- 1. Anatomy of Uvea Dr.SameekshaAgrawal
- 2. 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
- 3. Embryology IRIS- • Both layersof epithelium derived from marginal region of optic cup (neuroectoderm) • Sphincter and dilator pupillae- anterior epithelium (neuroectoderm) • Stroma and vessels- vascular mesoderm
- 4. Continued CILIARY BODY • BothEpithelium from neuroectoderm • Ciliary processes from ciliary epithelium • Stroma and blood vessels – mesoderm
- 5. Milestones • 9TH WEEKGESTATION- 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
- 6. Iris • Anterior mostpart • 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
- 7. Macroscopic structure TWO SURFACES A)ANTERIORSURFACE • Collarette- zigzag line, 2mm from pupil, thickest, represents attachment of pupillary membrane • Divides surface into- a) CILIARY ZONE- c/b Radial streaks- Due to underlying radial vessels Crypts- Depressions where suoerficial layers of iris is missing peripheral-near the iris central- near collarette Contraction furrows- faints lines outside collarette
- 8. Continued b) PUPILLARY ZONE- Betweencollarette and pigmented frill Pigmented frill- black pigment at pupillary margin - represents ant end of optic cup
- 9. Continued B)POSTERIOR SURFACE- darkbrown/black Contains- A) Schwalbe’s contraction folds- 1 mm from pupillary border, little radial furrows B) Schwalbe’s structural furrows- 1.5 mm from pupillary border. Narrow and deep to start with and become wide and shallow as they approach ciliary margin C) Circular furrows- finer then radial furrows. Crosses structural furrows at regular intervals. More marked near the pupil and formed due to difference in thickness of pigmented epithelium.
- 10. Microscopic structure FOUR LAYERS- a)Anteriorlimiting 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-
- 11. Continued 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
- 12. Continued 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
- 15. FUNCTIONS OF IRIS •Controls amount of light entering the eye through pupil • Defines eye colour • Control depth of field • Source of blood ocular to tissues
- 16. Ciliary Body • Forwardcontinuation 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 parts a) Anterior part- ciliary processes (pars plicata) 2-2.5mm b)Posterior part- smooth (pars plana) 5mm wide temporally & 3mm nasally
- 18. Microscopic Structure 1.SUPRACILIARY LAMINA-outermost part Consist of pigmented collagen fibres Posteriorly continuation of suprachoroidal lamina, ant continous with anterior limiting membrane
- 19. Continued 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
- 20. Continued 3)Layer of pigmentedepithelium- forward continuation of RPE Anteriorly continues to anterior epithelium of iris 4)Layer of non pigmented epithelium- forward continuation of sensory retina Continues anteriorly with posterior pigmented epithelium of iris 5)Internal limiting membrane-lines NPE Forward continuation of internal limiting membrane of retina
- 21. Ciliary Processes • Fingerlike projections from pars plicata • 70-80 in number, 2mm long 0.5mm diameter • Site of aqueous production ULTRASTRUCTURE 1)Network of capillaries- in the centre • Has endothelium with fenestrae 2)Stroma of ciliary processes- thin, separates capillaries from epithelium 3)Epithelium-two layered with apical apposition
- 22. Functions of ciliarybody • Site of aqueous humour production • Maintenance of IOP • Constitutes blood aqueous barrier • Accommodation
- 23. Choroid • Posterior mostpart • 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
- 24. Microscopic structure 1) Suprachoroidallamina- 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)
- 25. Continued 3) choriocapillaris- richcapillary network • Supplies pigment epithelium and outer layers of sensory retina • Few anastomosis with CRA 4)Basal lamina- bruch’s membrane • Innermost layer • Between choriocapillaris and RPE • Electron microscopy- basement membrane of RPE, inner collagen, middle elastic and outer collagen and basement membrane choriocapillaris
- 27. FUNCTIONS OF CHOROID •BLOOD SUPPLY TO OUTER LAYERS OF RETINA • ASSIST IN THE CONTROL OF INTRAOCULAR PRESSURE • PIGMENT ABSORBS EXCESS LIGHT SO AVOIDING REFLECTION
- 28. BLOOD SUPPLY UVEALTRACT 1.SHORT POSTERIOR CILIARY ARTERIES • Branches of ophthalmic artery • Divides into 10-20 branches, pierce sclera around optic nerve • Supply choroid in segmental manner 2) LONG POSTERIOR CILIARY ARTERIES • Two in number- nasal and temporal • Pierce sclera • Anastomose with anterior ciliary arteries- form major arterial circle supply ciliary body 3)ANTERIOR CILIARY ARTERIES • From muscular arteries • 7 in number • 2 each SR,IR,MR and 1 from LR • Anastomse with LPCA
- 31. VENOUS DRAINAGE Vena verticosae-4 in no. Drain whole of choroid
- 32. UVEITIS ( APPLIEDASPECTS) • Inflammation of uveal tract • Usually U/L • CLASSIFICATION- 1. ANTERIOR- iritis, iridocyclitis 2. INTERMEDIATE- cyclitis, pars planitis 3. POSTERIOR- retinitis, chorioretinits 4. PANUVEITIS
- 34. CONGENITAL ANOMALIES 1.HETEROCHROMIA IRIDUM 2.POLYCORIA-more then one pupil 3.CORECTOPIA- abnormally eccentric pupil
- 35. Continued 4. ANIRIDIA- abscenceof iris • o/e- a narrow rim of iris tissue behind sclera seen oftenly • zonules of lens and ciliary processes often visible 5. PERSISTENT PUPILLARY MEMBRANE- • Persistent part of ant vascular sheath of lens • Attached to collarate
- 36. Continued 5.COLOBOMA UVEA- defectin 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
- 38. Continued CYST OF IRIS-congenital cyst may arise from a)stroma b)pigment epithelium
- 39. BRUSHFIELD SPOTS INDOWNS SYNDROME LISCH NODULES IN NF1
- 40.