Uvea anatomy

This course is designed for bachelor optometry entrance preparation.

1. UVEA: ANATOMY, NERVE & VASCULAR SUPPLY

2. Introduction Embryology of the uveal tract Congenital anomalies of uveal tract Iris: anatomy and nerve supply Ciliary body: anatomy and nerve supply Choroid: anatomy Blood supply of uveal tract Clinical Correlation Presentation layout

3. Coined from latin word Uva - grape Middle vascular coat of eyeball From anterior to posterior: - iris - ciliary body - choroid INTRODUCTION

4. Uveal tract firmly attached to sclera only at 3 sites: the scleral spur the exit points of vortex veins the optic nerve

5. c Embryology

6. Milestones 9 th week of gestation Ciliary body begins to appear 12 th week of gestation Sphincter pupillae appears 4 th month Ciliary processes fully formed 5 th month Iris and choroid are formed 6 th month Dilator muscles begin to form Sphincter muscle fully differentiated Postnatal period dilator muscles reach adult proportion by 5 years

7. Congenital anomalies of uveal tract Aniridia ( Iridremia ) -congenital absence of Iris -true aniridia i.e complete absence of iris rare -a peripheral rim of iris present & this is called clinical Aniridia

8. Heterochromia of iris Heterochromia iridium Heterochromia iridis Color of one iris differs from the other One sector of iris differs from the remainder of iris

9. Uveal coloboma Typical coloboma : Located inferonasally in the region of closure of embryonic fissure Complete coloboma : Extends from pupil to optic nerve Includes retina, choroid, ciliary body, iris b. Incomplete coloboma : Involve the iris alone, or iris and ciliary body, or iris, ciliary body & part of choroid

10. Atypical coloboma Occasionally found in other positions i.e. not related to fissure closure It is usually incomplete Persistent pupillary membrane Represents the remnants of vascular sheath of lens Strands arise from and insert into the iris collarette .

11. IRIS Greek Word Iris - color haloes/rainbows Anterior most part of the uvea Diameter -12 mm Thickness -0.5 to 0.6 mm 3 to 4 mm aperture slightly nasally- pupil Attached to the middle of anterior surface of ciliary body Thinnest at root and tears easily- Iridodialysis

12. POINT TO BE NOTED Pupillary margin rests lightly on anterior surface of lens so when lens is removed the iris is flat and often tremendous

13. Macroscopic structure Anterior surface 1. ciliary zone: - radial steaks - crypts: peripheral & central - contraction furrows 2. pupillary zone: - about 1.6mm wide, lies between collarette and pigmented pupillary frill Collarette : represents the attachment of pupillary m/m lies 2mm from the pupil margin thickest region of iris

14. Posterior surface - dark brown or black - looks smooth under magnification: - schwalbe’s contraction folds : radial furrows, commence 1mm from pupillary border - schwalbe’s structural furrows : start 1.5mm from pupillary border, narrow and deep to start with but becomes wide and shallow as they approach the ciliary margin - circular furrows : finer than radial furrows cross the structural furrows at regular interval more marked near the pupil

15. Clinical correlation

16. Microscopic structure Anterior limiting layer Iris stroma Anterior epithelial layer Posterior pigmented epithelial layer

17. 1 . Anterior limiting membrane Condensed part of the stroma Consists of melanocytes and fibroblasts Deficient in areas of crypts, very thin at contraction furrows Determines the color of iris 3 types of intercellular junctions present - gap junctions - intermediate junctions - discontinuous tight junctions

18. 2. Stroma Main bulk of iris tissue Consists of loosely arranged collagenous network with mucopolysaccharide ground substance contains -the sphincter pupillae muscles - dilator pupillae muscles -the vessels and nerves of iris -cellular elements: fibroblast, melanocytes, clump cells and mast cells

19. Sphincter pupillae muscles - 0.7mm wide , 0.1-0.17mm thick Encircles pupillary margin lies in stroma deep to the surface - Even after broad iridectomy , which removes a sector of iris sphincter,the remaining sphincter can still constrict the remaining pupil margin Origin is from anterior epithelium,but actually separated from this layer by a thin sheet of collagen & dilator fibre processes, to which it is firmly bound. Innervated by parasympathetic via short ciliary nerve

20. Dilator pupillae muscle 60um long &7um wide Filled with myofilaments Extend from iris root towards pupil When the muscle contract,it pulls the pupillary margin towards the ciliary body, dilating the pupil - Innervated by sympathetics via long ciliary nerve At birth dilator is poorly developed &pupil response poorly to mydriatics

21. Parasympathetic Control of pupillary Size

22. Sympathetic Control of Pupillary Size:

23. Blood vessels - form bulk of iris stroma - they arise mainly from circulus arteriosis major - some also arise directly from anterior ciliary arteries - responsible for radial streaks seen on anterior surface of iris Peculiarities of iris : Absence of internal elastic lamina non fenestrated capillary endothelium

24. Cellular elements of stroma 1) Fibroblast most common stromal cell found around blood vessels, nerves, muscle tissue and throughout the iris substance 2) Melanocytes branching elements with processes contain melanin granules

25. 3) Clump cells large round pigment cells without processes filled with inclusion granules 4) Mast cells They are round Have villous processes Extracellular matrix of stroma Contain type VI collagen Laminin and fibronectin

26. 3. Anterior epithelial layer anterior continuation of pigment epithelium of retina and ciliary body lacking in melanocytes basal processes of the cells of this layer give rise to dilator pupillae muscle

27. 4. Posterior pigmented epithelial layer anterior continuation of non pigmented epithelium of ciliary body which in turn is the continuation of sensory retina this layer derived from the internal layer of optic cup contain abundant columnar type pigment cells It curves around the pupillary margin and extends for a short distance onto anterior border layer of iris stroma as the pigment ruff.

28. - In Rubeosis iridis , this pigmented layer extends farther onto the anterior surface of the iris, a condition called Ectropion uveae Clinical significance

29. Forward bowing of iris Angle closure glaucoma Contact betweet the posterior surface of iris and lens creates a relative pupillary block to the flow of aqueous humor through the pupil,which is more marked in mid dilatation

30. Applied anatomy Iris nodules Accumulated deposits of epithelioid cells and lymphocytes deposited onto the iris without tissue destruction. Two types: Koeppes nodule at pupillary border Busaccas nodules near collarette

31. Iris atrophy areas of degeneration of iris Commonly seen in iridocyclitis

32. Forward continuation of the choroid at ora serrata . In cut section, triangular in shape CILIARY BODY

33. Anterior side of triangle- part of anterior chamber angle in middle- attached to the iris Outer side of triangle lies against the sclera with a suprachoroidal space in between Inner side of triangle divided into 2 parts: 1) pars plicata - anterior 2) pars plana - posterior

34. 1) Pars plicata / corona ciliaris anterior part about 2 to 2.5 mm long contain ciliary muscles have finger like ciliary processes 2) Pars plana / orbicularis ciliaris posterior smooth part 5mm wide temporally 3 mm wide nasally Viterous base gain attachment to the epithelium of pars plana

35. Microscopic structure From without inwards, consists of five layers: 1) Supraciliary lamina 2) Stroma of the ciliary body 3) Layer of pigmented epithelium 4) Layer of non-pigmented epithelium 5) Internal limiting membrane

36. 1) Supraciliary lamina outermost condensed part of stroma consists of pigmented collagen fibres Posteriorly,continuation of suprachoroidal lamina Anteriorly, continues with the anterior limiting membrane of iris 2) Stroma of the ciliary body consists of collagenous connective tissue and fibroblast embedded in it: a. ciliary muscle b. blood vessels c. nerves d. pigment cells & other cells

37. Ciliary muscle non striated, smooth muscle occupies most of the outer part of the ciliary body three main groups: 1) the longitudinal or meridional fibres 2) the oblique or radial fibres 3) the circular fibres

38. 1) Longitudinal or meridional fibres - most external and closest to the sclera pass posteriorly into the stroma of ciliary body 2) Oblique or radial fibres - occupy the midportion of the ciliary body radiate out from the scleral spur 3) Circular fibres - occupy anterior and inner portion of the ciliary body - nearest to the lens runs parallel to the limbus - directly act as sphincter

39. Main action of all parts of ciliary muscles is to slacken the suspensory ligament of lens & thus helps in accommodation. Longitudinal muscle fibres form tendinous attachment to the scleral spur: contraction increases aqueous flow by opening up the spaces of trabecular meshwork

40. Contraction of the ciliary muscle, especially longitudinal and circular fibres pulls the ciliary body forward in accommodation.

41. Vascular stroma -contain major arterial circle just in front of circular fibres of the muscle - Arterial circle is formed by the anastomosis between the long posterior ciliary arteries and anterior short ciliary arteries and send branches to iris and ciliary body

42. 3) Layer of pigmented epithelium forward continuation of RPE anteriorly, continuous with anterior epithelium of iris 4) Layer of non-pigmented epithelium consists mainly of low columnar or cuboidal cells forward continuation of sensory retina which stops at ora serrata . continues anteriorly with posterior pigmented epithelium of the iris

43. 5) Internal limiting membrane lines the non-pigmented epithelium forward continuation of internal limiting membrane of the retina.

44. Nerve supply of the ciliary body these run from the nasociliary branch of the ophthalmic division of the trigeminal nerve, running in the long ciliary nerve these fibres enter the ciliary body and terminate in iris, cornea and ciliary muscle. Sensory fibres :

45. Sympathetic fibres : Parasympathetic fibres

46. Ciliary processes Whitish finger-like projections from pars plicata part of the ciliary body 70 to 80 in number Each process is about 2mm long and 0.5mm in diameter Form the site of aqueous production

47. Ultrastructure of ciliary processes Consists of: The network of capillaries Stroma of ciliary processes Two layers of epithelium

48. a. The network of capillaries occupies the centre of each process each capillary consists of a very thin endothelium with fenestration lined by basement m/m mural cells or pericytes present within basement membrane

49. b) Stroma of the ciliary process very thin separates capillary network from epithelial layers consists of ground substance: mucopolysaccharide , proteins & solute of plasma few collagen connective tissue fibres wandering macrophages

50. c) Two layers of epithelium their apical surfaces in apposition to each other outer pigmented epithelium: contains numerous melanin granules inner non-pigmented epithelium: contain mitochondria, zonula occludentes & lateral and surface interdigitations . the tight junction between cells of this layer form blood aqueous barrier

51. Posterior portion of the middle vascular coat Extremely vascular Extends from optic disc to ora serrata The inner surface: smooth, brown and lies in contact with RPE The outer surface: rough and attached to sclera Posteriorly-0.22 mm thick anteriorly-0.1 mm CHOROID

52. Firmly attached to the margin of the optic disc Loosely at points where vessels and nerves enter it Attachment to sclera is strongest behind the sclera

53. Microscopic structure From without inwards, consists of four layers: 1) Suprachoroidal lamina (lamina fusca ) 2) Stroma of the choroid 3) Choriocapillaries 4) bruch’s membrane (basal lamina or lamina vitrae )

54. 1) Suprachoroidal lamina thin membrane 10 to 34 μ m made of condensed collagen fibres , melanocytes and fibroblasts continues anteriorly with supraciliary lamina space between this m/m and sclera: suprachoroidal space (contain long & short posterior ciliary arteries and nerves)

55. -contains vessels, nerves, cells & connective tissue -stromal cells include: a. melanocytes b. fibrocytes c. macrophages d. mast cells e. plasma cells 2) Stroma of the choroid Main bulk is formed by vessels, arranged in two layers: a. Haller’s layer: outer layer of large vessels b. Sattler’s layer: inner layer of medium vessels

56. consists of a rich bed of wide bore fenestrated capillaries (18 to 50 μ m) receives most of its blood from medium & large vessels of stroma nourishes RPE & outer layers of sensory retina density greatest at macula 3) Choriocapillaries choriocapillaries are divided into non overlapping lobules or hexagonal patches

57. innermost layer of choroid thin non cellular lamina lies between choriocapillaries and pigment epithelium of the retina 2 to 4 μ m thickness 4) Bruch’s membrane

58. Comprises of five layers a. Basal lamina of RPE b. Inner collagen layer c. Middle elastic layer d. Outer collagen layer e. Basal lamina of choriocapillaries

59. Choroidal ischaemia often occurs as a pale hexagonal patches (mosaic pattern) during choroidal phase of FFA, these lobules fill independently from one another, giving a transiently patched or blotched appearance Clinical significance

60. Bruchs membrane become thickened with increasing age and produces hyaline excrescence known as drusens

61. Uveal tract supplied by 3 sets of arteries: 1) Short posterior ciliary arteries 2) Long posterior ciliary arteries 3) Anterior ciliary arteries BLOOD SUPPLY OF THE UVEAL TRACT

62. 1) Short posterior ciliary arteries

63. 2) Long posterior ciliary arteries

64. 3) Anterior ciliary arteries

65. four in number (superior temporal, inferior temporal, superior nasal and inferior nasal) pierce sclera obliquely on each side of SR and IR muscles about 6 mm behind the equator -drain blood from: whole of choroid receive small veins from ONH small veins from retina from iris, ciliary process, ciliary muscle, anterior part of choroid 3) Venae vorticosae (vortex veins or posterior ciliary veins)

66. two superior vortex veins open into superior ophthalmic vein two inferior vortex veins open into inferior ophthalmic vein

67. Uveitis: Inflammation of uveal tissue only Classification: 1.Anterior uveitis: Some clinically applied aspects Inflammation of uveal tissue from iris upto pars plicata of ciliary body - Iritis : inflammation predominantly affect iris Iridocyclitis : iris and pars plica part of ciliary body are involved Anterior cyclitis : pars plicata part of ciliary body is predominantly affected

68. 2. Intemediate uveitis: Inflammation of pars plana and peripheral part of retina and underlying choroid 3. Posterior uveitis: Inflammation of choroid and retina Hence the term choroiditis , chorioretinitis , retinochoroiditis or neurouveitis is used 4.Panuveitis: Inflammation of whole uvea

69. Salient features of uveitis

70. Complications of uveitis

71. Aqueous cells: -presence of inflammatory cells in the anterior chamber -the inflammatory response causes white blood cells such as neutrophils, monocytes and lymphocytes to leave the inflamed iris vessels to reach aqueous humour .

72. Aqueous flare Turbidity of the aqueous humour caused by increased protein level Blood aqueous barrier breakdown results in protein (albumin) exudation in the anterior chamber giving the normally clear, colorless aqueous humour a milky appearance k/a flare

73. References