Anatomy of uvea

Uvea - iris, ciliary body, choroid

1. Anatomy of Uvea Dr.Sameeksha Agrawal

2. Introduction UVEA constitutes- middle vascular coat 3 parts- a)iris b) ciliary body c)choroid Developmentally,structurally and functionally- indivisible C olor varies from light blue to dark brown

3. 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

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

5. Milestones 9 TH WEEK GESTATION- ciliary body appears 12 TH WEEK GESTATION- sphincter pupillae appears 5 TH MONTH- all layers of choroid seen - iris fully developed 6 TH 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 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

7. Macroscopic structure TWO SURFACES A)ANTERIOR SURFACE Collarette - zigzag line, 2mm from pupil, thickest, represents attachment of pupillary membrane Divides surface into- 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- Between collarette and pigmented frill Pigmented frill- black pigment at pupillary margin -represents ant end of optic cup

9. Continued B)POSTERIOR SURFACE- dark brown/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)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-

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

13. 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

14. 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 parts a) Anterior part- ciliary processes ( pars plicata ) 2-2.5mm b)Posterior part- smooth ( pars plana ) 5mm wide temporally & 3mm nasally

15. Microscopic Structure 1.SUPRACILIARY LAMINA- outermost part Consist of pigmented collagen fibres Posteriorly continuation of suprachoroidal lamina, ant continous with anterior limiting membrane

16. 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

17. Continued 3)Layer of pigmented epithelium- 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

18. Ciliary Processes Finger like 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

19. Functions of ciliary body Site of aqueous humour production Maintenance of IOP Constitutes blood aqueous barrier Accommodation

20. 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

21. 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 )

22. Continued 3) choriocapillaris - rich capillary 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

23. FUNCTIONS OF CHOROID BLOOD SUPPLY TO OUTER LAYERS OF RETINA ASSIST IN THE CONTROL OF INTRAOCULAR PRESSURE PIGMENT ABSORBS EXCESS LIGHT SO AVOIDING REFLECTION

24. BLOOD SUPPLY UVEAL TRACT 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

25. VENOUS DRAINAGE Vena verticosae - 4 in no. Drain whole of choroid

26. UVEITIS ( APPLIED ASPECTS) Inflammation of uveal tract Usually U/L CLASSIFICATION- ANTERIOR- iritis , iridocyclitis INTERMEDIATE- cyclitis , pars planitis POSTERIOR- retinitis, chorioretinits PANUVEITIS

27. CONGENITAL ANOMALIES 1.HETEROCHROMIA IRIDUM 2.POLYCORIA - more then one pupil 3.CORECTOPIA - abnormally eccentric pupil

28. Continued 4 . ANIRIDIA- abscence of 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

29. Continued 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

30. Continued CYST OF IRIS- congenital cyst may arise from a) stroma b)pigment epithelium

31. BRUSHFIELD SPOTS IN DOWNS SYNDROME LISCH NODULES IN NF1

32. Thank you