UVEAL TRACT

1-IT IS A MIDDLE VASCULAR COAT OF EYEBALL.
2-IT MAINLY CONSIST OF THREE PARTS IRIS, CHOROID, CILIARY BODY.
3- CILIARY BODY CAN HOLD THE LENS AND PLAY IMPORTANT ROLE IN ACCOMODATION.

1. UVEAL TRACT

2. Uveal tract Uvea known as middle vascular coat of eyeball . Anterior to posterior it can be divided into three parts--- Iris Ciliary body Choroid Note– Uvea is a Greek word meaning Grapes.

3. IRIS Anterior part of the uveal tract. Forms diaphragm like structure in front of lens. Center of iris has an 3-4 mm aperture called Pupil. At periphery it is attached to the anterior surface of ciliary body. Divides the space between the cornea and lens into anterior and posterior chamber.

4. Topography of iris Average diameter of the iris is 10 to 11 mm. The thickness of iris root is approximately 0.5 mm. It is thickest at collarette, which is located approximately 1.5 mm from the pupillary margin It is thinnest at iris root, the part of iris which joins with the ciliary body

5. Embryology Both layer of epithelium is derived from marginal region of optic cup. (Neuroectoderm) Sphincter and dilator pupillae muscle derived from anterior epithelium . (Neuroectoderm) Stroma and vessels developed from vascular mesoderm present anterior to optic cup.

6. Macroscopic appearance Anterior surface— Divided into cilary and pupillary zone by zigzag line called collarette. It is the thickest region of the iris which lies about 2 mm from the pupil margin.

7. Cilliary zone- It extend from the collarette to iris root. There are some depressions or pit arranged in rows present in this area known as crypts. Crypts are found in two locations. Those present near collarette are relatively larger and known as Fuchs’s crypt and few are seen in periphery of the ir is Pupillary Zone- It lies between the collarette and pigmented pupilary frill It is 1.6 mm wide,relatively smooth and flat .

8. POSTERIOR SURFACE Posterior surface of the iris is much more uniform. Posterior surface of the iris is darker than the anterior surface and shows numerous radial contraction folds .

9. MICROSCOPIC STRUCTURE Microscopically iris consist of four layers Anterior limiting membrane. 2- Iris stroma 3- Anterior epithelium layer 4-- Posterior pigmented epithelium layer .

10. 1. Anterior limiting layer : It lines the iris and is the anterior most condensations of iris stroma. The layer consist of mainly fibroblasts and melanocytes. Previously, this layer is known as ENDOTHELIAL LAYER . This layer is mainly responsible for the colouring action of iris. 2. Iris stroma :   Iris stroma forms the main bulk of iris tissue and contains sphincter pupillae, dilator pupillae muscles, vessels and nerves. 3. Anterior epithelium layer : It is the anterior continuation of the pigmented epithelium of retina and ciliary body. 4. Posterior pigmented epithelium layer - Anterior continuation of the non- pigmented epithelium of the ciliary body and the sensory retina

11. CILIARY BODY It is the anterior portion of the uveal tract , which is located b/w the iris and the choroid. middle part of vascular coat of eyeball. Triangular in shape. Inner side of triangle is divided into two parts. The anterior portion - pars plicata The posterior portion- pars plana The outer side of triangle lies against the sclera. composed of muscles , vessels and epithelium.

12. EMBRYOLOGY Both epithelial layer of ciliary body develop from the anterior part of the two layers of optic cup. (neuroectoderm) Stroma of the ciliary body , ciliary muscle and blood vessels are developed from the vascular layer of mesenchyme surrounding the optic cup.

13. Microscopic structure Microscopically ciliary body consist of five layers. Supraciliary lamina. Stroma. Layer of pigmented epithelium. Layer of non pigmented epithelium. Internal limiting membrane.

14. Supraciliary lamina – outermost condensed part of the stroma consist of pigmented collagen fibres . Anteriorly become continues with the anterior limiting membrane of iris. posteriorly , it is the continuation of the suprachoroidal lamina. Stroma— Consist of connective tissue of collagen and fibroblast. Ciliary muscle, vessels, nerves and cells are embedded in stroma. Layer of pigmented epithelium- Forward continuation of the retinal pigmented epithelium. Anteriorly become continues with the anterior pigmented epithelium of iris.

15. Layer of non pigmented epithelium- Forward continuation of sensory retina. Continues anteriorly with the posteriorly pigmented epithelium of iris. Internal limiting membrane- Forward continuation of the internal limiting membrane of the retina. Lines the non-pigmented epithelial layer.

16. Ciliary process Finger like projection from the pars plicata part of the ciliary body. They are white in color Process is lined by two layer of epithelial cell . It contain blood vessels and loose connective tissue these process are the site of aqueous production. Each process is about 2 mm long and 0.5 mm in diameter. They are about 70 to 80 in numbers.

17. Ciliary muscle Occupies most of the outer part of the ciliary body. These are non striated muscle having three parts Meridional fibers- Help in aqueous outflow. Circular fibers - Help in accommodation. Oblique fibers - Help in Aqueous outflow. Ciliary muscle is supplied by parasympathetic fibers through the short ciliary nerves . Action- Main action is to slacken the suspensory ligament of the lens and thus help in accommodation.

18. Embryology Mainly derived from the inner vascular layer of the mesenchyme that surrounds the optic cup Melanocytes of choroid originate from the neural crest.

19. Microscopic structure of choroid Choroid consist of four layers. Suprachoroidal lamina. Stroma.   Choriocapillaris.   Bruch's membrane.  

20. 1.Suprachoroid lamina (lamina fusca): Thin membrane of condensed collagen fibers, melanocytes and fibroblast. It consist of potential space between sclera and choroid known as supra choroidal space . The potential space contains the long posterior ciliary arteries and nerves. 2. Choroidal stroma: Consist of loose collagenous tissue with some elastic and reticular fibers. Contain pigmented cells and plasma cells. It forms the main bulk of the choroid. It consist of two types of vessels Medium vessels and large vessels

21. 3. Layer of Choriocapillaris It nourishes the pigmented epithelium and outer layer of sensory retina. Choriocapillaries contain a basement membrane . Receive blood from medium and large vessels of stroma. The capillary walls are fenestrated and contains pericytes 4. Bruch's membrane: innermost layer of choroid having thickness 2-4 mm. Multilayered structure lies between the choriocapillaris and pigmented epithelium of retina. It consist of five layers:- Basement membrane of retinal pigmented epithelium Inner collagen fibers Middle elastic fibers Outer collagen fibers Basement membrane of choriocapillaries

22. Blood supply of uveal tract The uveal tract is supplied by three sets of artery. Short posterior ciliary artery- Arises as two trunks from the ophthalmic artery . It pierce the sclera around the optic nerve and supply the choroid in a segmental manner. Long posterior ciliary artery-- two in number nasal and temporal . Pierce the sclera obliquely on medial and lateral side of the optic nerve and supply the ciliary body. Anterior ciliary artery– Derived from muscular branches of ophthalmic artery. 7 in numbers– 2 each of superior, medial, inferior rectus muscle and one from lateral rectus muscle these artery gives branches to sclera , limbus and conjunctiva.

23. NERVE SUPPLY The iris receives its sensory and autonomic nerve supply from the long and short ciliary nerves. The long ciliary nerves are branches of the nasociliary branch of the ophthalmic division of the trigeminal nerve. These fibers innervate the dilator pupillae. • The short ciliary nerves arise from the ciliary ganglion and contain postganglionic parasympathetic nerve fibers. The parasympathetic innervates the sphincter pupillae.

24. The choroid is innervated by the long and short ciliary nerves. The long ciliary nerves are branches of the nasociliary nerves, a branch of the ophthalmic division of the trigeminal nerve. (sensory & parasympathetic) – The short ciliary nerves arise from the ciliary ganglion and carry parasympathetic fibers and sympathetic fibers.   The ciliary muscle is innervated by the postganglionic parasympathetic fibers derived from the oculomotor nerve; The nerve fibers reach the muscle via the short ciliary nerves.

25. UVEITIS Also known as Iridocyclitis. Inflammation of uveal tissue. Common cause of blindness. Associated with systematic autoimmune disease. Symptoms and signs Ciliary flush Burning of the eye Redness of the eye Blurred vision Photophobia or sensitivity to Light. Irregular pupil.

26. ENDOPHTHALMITIS It is an inflammation of the internal coats of the eyeball It is a possible complication of all intraocular surgeries, particularly cataract surgery, with possible loss of vision and the eye itself . CAUSES- Bacterial and fungal infection penetrating trauma allergic reaction Symptoms- severe pain loss of vision redness of the conjunctiva Photophobia Management- Topical therapy Subconjunctival infections Intravitreal injection.

27. panophthalmitis Inflammation of the whole eyeball including tenon’s capsule. Eyeball is filled with pus Uveal tract is infiltrated with inflammatory cells like WBC. Symptoms- Ocular pain Headache Complete loss of vision Swelling of eyes. Management- anti-inflammatory and analgesics should be started immediately. use broad spectrum of antibodies to prevent further spread of infection.