The vascular coat of the eye

Eye anatomy and physiology of our eye presentation.

1. THE VASCULAR COAT OF THE EYE ANIS SUZANNA BINTI MOHAMAD OPTOMETRIST

2. WALL OF THE EYE Fibrous ( outer ): sclera, cornea Vascular ( middle ): choroid, ciliary body, iris Nervous ( inner ): retina

3. VASCULAR TUNIC The middle coat of eyeball a.k.a uvea Vascular & pigmented Functions: Regulates light entry & anchors the lens Absorbs reflected light Nourishes retina Components: Iris Ciliary body Choroid

4. 1. IRIS

5. 1. IRIS Thin, pigmented contractile circular structure Analogous to the diaphragm of a camera Lies on anterior lens surface, surrounded by aquos humor Extends from iris root to iris margin that forms the pupil The free edge is known as pupillary margin Separates anterior segment ant & post chambers which are continuous through pupil Stroma of iris is continuous with stroma of ciliary body Muscles: pupillary sphincter m. & pupillary dilator m. (circular) (radial)

6. 1. IRIS Color depends on density of pigment & collagen in anterior limiting layer & stroma Heavily pigmented : brown eyes Lightly pigmented : lighter iris ranges from gray-blue-green Albino iris contains no pigment either in connective tissue cells ( stroma ) or in pigment layer Iris appears delicate pink with associated problems due to oversensitivity to light

7. 1. IRIS Dimensions: Average diameter : 12mm – varies with lighting Thickness : 0.5mm Thickest at collarette Collarette divides ant iris into pupillary & ciliary zones Thinnest at the root Thin regions eg iris root & margin are more susceptible to tearing in injuries Rough anterior surface & smooth posterior surface

8. 1. IRIS – 4 layers 1. Anterior limiting layer 2. Stroma & sphincter muscle 3. Anterior epithelium & dilator muscle 4. Posterior epithelium

9. 1. IRIS – 4 layers 1. Anterior border layer : Thin, discontinuous (cryptic) Composed of collagen fibrils & fibroblasts Underlying melanocytes

10. 1. IRIS – 4 layers 2. Stroma & sphincter muscle Loose, pigmented, highly vascular connective tissue Pigmented epithelium lining the posterior surface Composed of pigmented & non-pigmented cells, collagen fibrils & extensive ground substance Pigmented: melanocytes & clump cells Non-pigmented: fibroblast, lymphocyte, macrophage, mast cells Amount of melanocytes in stroma determines eye color Sphincter muscle: lies in stroma , near pupil, concentrically arranged, contraction causes pupil constriction ( miosis ) Innervated by oculomotor , parasympathetic nervous system

11. 1. IRIS – 4 layers 3. Anterior epithelium & dilator muscle Composed of unique myoepithelial cells Dilator muscle: Smooth m. which extends into stroma forming 4-5 layers From iris root to a point in stroma below sphincter midpoint Radially arranged Contraction causes pupil dilatation ( mydriasis ) – innervated by sympathetic nervous system

12. 1. IRIS – 4 layers 4. Posterior epithelium Single layer of heavily pigmented simple columnar cells At posterior, continuous with inner non-pigmented epithelial layer of ciliary body Curled to anterior surface at pupil margin – pupillary ruff

13. Pupillary ruff Pigmented epithelium Dilator muscle Circular muscle Blood vessels

14. 1. IRIS – recap on pupil movement Mydriasis Pupil dilation Dilator pupillae m. Radially arranged Sympathetic innervation Conditions: Dark Fear Excitement Mydriatics ? Miosis Pupil constriction Sphincter pupillae m. Circularly arranged Parasympathetic innervation Conditions: Bright illumination Sleeping Convergence Miotics ?

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16. EYE vs CAMERA

17. 2. CILIARY BODY End of choroid, connects choroid to iris circumference Muscular & vascular Functions: Aquous humor production (via non-pigmented epithelium) Control of lens accommodation (via ciliary muscles)

18. 2. CILIARY BODY Anterior view: ring-shaped structure Sagittal view: triangular shape Base faces anterior chamber Apex at ora serrata 2 surfaces: Pars plicata : Wider anterior portion containing 70-80 ciliary processes extending into posterior chamber Pars plana : Flat ter region extending from posterior of pars plicata to ora serrata

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20. 2. CILIARY BODY Ora Serrata Transition between c.body & choroid Serrated pattern Non pigmented ciliary epithelium undergoes sharp transition to become the neural retina Ciliary processes 70-80 finger-like projections radiating from pars plicata Occupy peripheral part of posterior chamber Grooves in between serve as attachment for lens zonules Each process is about 2mm long and 0.5mm in diameter

21. 2. CILIARY BODY 3 structures: c. muscle, c. stroma , c. epithelium 1. Ciliary muscles – 3 groups of smooth muscle fibers Longitudinal (outermost) Radial Circular (innermost) 2. Ciliary stroma Highly vascularised loose connective tissue Anteriorly continuous with iris stroma Posteriorly continuous with choroidal stroma Thin in pars plana

22. 2. CILIARY BODY 3. Ciliary epithelium (innermost part of ciliary body) 2 layers of cells: pigmented & non-pigmented epithelial cells 1. Pigmented epithelium ( outer – next to stroma ) - Anterior part continuous with anterior iris epithelium 2. Non-pigmented epithelium ( inner – faces post chamber) - Columnar cells in pars plana , cuboidal cells in pars plicata - Anterior part continuous with posterior iris epithelium - Produces aquous humor & glycoprotein of vitreous - Diffusion barrier between blood & aquous

23. 3. CHOROID Thin, highly pigmented, vascular loose connective tissue Rich in melanocytes gives characteristic dark color Situated between sclera & retina Extends from optic nerve to ciliary body (at ora serrata ) Thickness decreases from post (0.22mm) to ant (0.1mm)

24. 3. CHOROID Functions: Nourishment for adjacent retina Block light entering through sclera, retain light entering through pupil 4 histological parts: 1. Suprachoroidal lamina 2. Choroidal stroma 3. Choriocapillaris 4. Bruch’s membrane

25. 3. CHOROID 1. Suprachoroidal lamina Transition zone of choroid & sclera Consists of melanocytes , fibroblasts & conn . tissue fibers Blends with choroid & lamina fusca of sclera Carries long posterior ciliary arteries & nerves

26. 3. CHOROID 2. Choroidal stroma Layer of pigmented, vascularised loose connective tissue Contains melanocytes , fibroblasts, macrophages, mast cells Arteries are branches of short posterior ciliary arteries Veins drain via vortex veins into ophthalmic veins

27. 3. CHOROID 3. Choriocapillaris layer Consists of rich capillary network Nourishes outer retina ( eg PR) – damage will affect retina Capillaries are fenestrated Extends anteriorly to ora serrata Greatest density of capillaries at macula

28. 3. CHOROID 4. Bruch’s membrane Extend from optic nerve head to ora serrata Thin refractile connective tissue membrane between choriocapillaris (choroid) and RPE (retina) Constitutes outer limit of retina Prevents choroid vessels from penetrating the retina but allows nutrients, proteins etc

29. RELATED DISORDERS Uveitis : inflammation of uveal tract eg . Iritis , choroiditis Age-related macular degeneration (AMD) Drusen (yellow deposits) in Bruch membrane at macula Horner’s syndrome: loss of symp innervation to the head Causes ptosis , anhydrosis , miosis Malignant choroidal melanoma

30. * tHE END *