Uvea tract and their presentations. They are so important for blood supply to the retina as well as preventing infection to the retina. This is important topic for undergraduates as well as masters students. I dedicate this work to all ophthalmology students across the globe.

1. UVEA TRACT
Presenter: Dr. Mlaluko Rajabu
SHOs, Mmed Ophthalmology
Makerere University
10/16/2023 Mlaluko MD 1

2. Outlines
Definition of Uvea tract
Components of uvea tract
Embryological development
Anatomy of Iris and applied anatomy
Anatomy of ciliary and applied anatomy
Anatomy of choroid and applied anatomy
Blood and nerve supply to uvea tract
10/16/2023 Mlaluko MD 2

3. Definition
• Is the vascular and pigmented middle layer of
the eye.
• Uvea derived from Latin which means grape,
• A.k.a uvea, vascular tunic of the eye, tunica
vasculosa bulbi, tunica vasculosa oculi
(Encylopedia)
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4. Cont…
• Divided into the anterior uvea (iris, ciliary
body) and posterior uvea (choroid).
• The uvea is sandwiched between an outer layer
(sclera) and an inner layer (retina). The
anterior segment is separated from the
posterior segment by the lens.
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5. Cont…
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6. Embryology
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• They develop from diencephalon,
• At 25 days the optic vesicles appears,
• Neural crests forms choroid, stroma of iris and
ciliary muscles,
• Posterior epithelium of iris, dilator pupillae
and sphincters from neuroectoderm,

7. Cont…
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8. Anatomy of Iris
• Is the anterior part of the uvea tract,
• It has the several parts; Pupillary ruff, collarete
(iris frill), Fuch’s crypts, pupillary region,
ciliary margin and iris root.
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9. Cont…
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10. Cont…
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11. Cont…
• Horizontal visible iris diameter (HVID) is about
10-14 mm (avg 11.6mm)
• Thickest at collarete (1.5mm). Site of foetal
pupillary membrane attachment
• The root is at the middle of ciliary body,
• The root is thickest at 0.5mm. Rips during blunt
traumaD-shaped pupil
• The pupillary margin is marked by dark border
called pupillary ruff; terminal pigmented layer
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12. Cont…
• Collarete divides the iris into pupillary and
ciliary region
• On the ciliary region; crypts and fewer on the
periphery of the iris,
• Crypts is the thinnest ; Laser iridotomy.
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13. Cont…Layers
• It has 5 layers; anterior limiting boarder, iris
stroma, muscular layer, anterior
myoepithelium, posterior pigment epithelium.
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14. Cont…Layers
Anterior limiting layer
• Is the anterior most condensations of iris
stroma,
• Mainly by fibroblasts and melanocytes
arranged in meshwork,
• Fibroblasts on the surface and melanocytes
beneath,
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15. Cont…Layers
• The colour of the iris depends on the thickness
of the this layer and melanocytes dispersed in
anterior limiting layer,
• Determinants of iris colour; density and
structure of iris stroma, pigment epithelium,
pigment content (granules) within the
melanocytes of iris stroma.
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16. Applied clinical anatomy
• Heterochromia;
Total and partial (sectoral/central)
• Rubeosis iridis
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17. Cont…
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18. Cont…
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19. Cont…Layers
Iris stroma
• It is mainly made up of collagens, fibril and
matrix (hyaluronic acid).
Components
• Pigmented cells; melanocytes+clump cells
• Non-pigmented cells; fibroblasts+clump cells
(lymphocytes, mast cells and macrophages)
• Nerves
• Blood vessels; radial arrangement from major
arterial cycle of iris
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20. 10/16/2023 Mlaluko MD 20

21. Cont…Layers
Muscular layer
• It consists of smooth muscles
• Derived from anterior pigment epithelium
• CircularSphincter pupillae
• RadialDilator pupillae
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22. Cont…
Sphincter pupillae
• Pupillary zone of iris,
• Firmly adhered to the iris stroma,
• 0.75-1 mm wide, 1.7 mm thick,
• Thicker than dilators,
• It consists of spindle shaped cells oriented
parallel to pupillary margin,
• ParasymphatheticCN III
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23. Cont…
Dilator pupillae
• It extends from iris root to a point in the stroma
below the mid-point of the sphincter,
• Dense band of connective tissue separates the
sphincter and dilators,
• Mydriasis
• Symphathetic innervation
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24. Cont…
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25. Cont…Layers
Anterior myoepithelium
• Specialized myoepithelial cells,
• Cell apex faces posterior segment,
• Basal surface composed of elongated contractile
smooth muscle processes,
• Continues as pigmented epithelium of ciliary
body
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26. Cont…Layers
Posterior pigment epithelium
• Densely pigmented velvety smooth,
• Curves around the pupillary margin to create a
pupillary ruff,
• Basal surface borders the posterior chamber,
apical faces the stroma and adheres to the
anterior pigment layer,
• Continue with non-pigmented epithelium of
ciliary body and neurosensory retinal layer.
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27. Clinical importance
Pigmentary dispersion syndrome
• Bilateral, characterized by liberation of pigmentary
granules from iris pigment epithelium,
• Due to mechanical rubbing of the posterior
pigment layer of iris against lens zonules as a result
of excessive posterior bowing of mid-peripheral
portion of the iris,
• Pigment epithelium itself may be abnormally
susceptible to pigment shedding.
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28. Cont…
Pseudoexfoliation syndrome
(PXF or PEX)
•Age-related systemic syndrome
associated with gradual deposition of
fibrillary white-flaky material from the
lens, mainly on the lens capsule, ciliary
body, zonules, corneal endothelium,
iris and pupillary margin.
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29. Cont…
• Open angle glaucoma in about 50% of these
patients
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30. Ciliary body
• It is a ring shaped structure which projects
posteriorly from the scleral spur,
• Brown due to pigment,
• Width 5.9mm (nasally), 6.7mm on temporal
side
• Anteriorly, it confluent with iris root as well as
it bounds part of AC.
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31. Cont…
• Posteriorly, has crenated periphery known as
Ora serrata where it is continuously with
choroid and retina,
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32. Cont…
• In cross-section, it is triangular in shape,
• Outer, attached to scleral with suprachoroidal
space between,
• Anterior, iris root and AC,
• Inner, divided into 2mm pars plicata (corona
ciliaris) and 4mm pars plana (orbicularis
ciliaris)
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33. Cont…
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34. Cont…
Pars plicata
• Rich in blood vessels,
• Has 70 to 80 ciliary processes which extends to
PC,
• Due ciliary processes, Pars plicata has SA of
6cm2 makes it 5 times than corneal endothelium,
• Region between processes are called valleys of
Kuhnt,
• Ciliary processes are 2mm (length), 0.5mm
(width) and 1mm (height)
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35. Cont…
Pars plana
• Flat or smooth part of the ciliary body
• Terminates at Ora serrata, which is transitional
zone between ciliary body and choroid,
• Inner, non-pigmented epithelium,
• Outer, pigmented epithelium which continues
with neurosensory retina,
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36. Cont…
Ora serrata
• Termed as anterior border of the neurosensory
retina
• It corresponds with insertion for LR and MR
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37. Layers of ciliary body
Has five layers
• Internal limiting layer
• Non pigmented epithelium
• Pigmented epithelium
• Stroma
• Supraciliary membrane
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38. Layers of ciliary body
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39. Layers of ciliary body
Internal Limiting Membrane
• It is the first layer of ciliary body,
• It acts as forward continuation of internal
limiting membrane of retina,
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40. Cont…
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41. Layers of ciliary body
Ciliary epithelium
Non-pigmented epithelium
• Extends from iris root to Ora serrata,
• Begins as continuation of posterior pigmented
epithelium of iris near iris root,
• At ora serrata, continues as Neurosensory retina,
• Gives origin to parts of zonules,
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42. Cont…
Pigmented epithelium
• 8 to 10μm wide and contain large pigment
granules and mitochondria,
• Granules are 3 to 4 times larger than those of
choroid and retina,
• Rich in organelles and metabolically active,
• Secretes BM which continues posteriorly with
RPE,
• Helps in active secretion of aqueous humor.
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43. Cont…
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44. Cont…
Ciliary stroma
• Contains blood vessels, nerves and ciliary
muscle,
• Anteriorly, continues with iris stroma,
• Posteriorly, continues with choroidal stroma
after thinning at pars plana,
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45. Cont…
Blood vessels in ciliary stroma
• Major arterial circle of iris, formed by
anastomosis of LPCA and ACA; located in ciliary
stroma near iris root just in front of circular
portion of ciliary muscle,
• Also consists of numerous of capillaries which are
fenestrated and large in size,
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46. Cont…
• Capillaries are more in ciliary processes,
making them the worst vascular organ of the
eye
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47. Cont…
Muscles in ciliary stroma; ciliary muscles
• Smooth muscles primarily in anterior 2/3 of
ciliary body stroma,
• Outer, longitudinal (Brucke’s muscle)
• Middle, oblique (reticular or radial)
• Inner, circular portion (Muller’s muscle)
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48. Cont…
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49. Cont…
Superciliary lamina
• Outer most layer of ciliary body which lies
adjacent to the sclera.
• Consists of pigment collagens,
• Due to lamellar arrangement of connective
tissues in this area, it acts as potential space,
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50. Cont…
• Anteriorly, anterior limiting membrane of iris,
• Posteriorly, Suprachoroidal lamina,
• Helps aqueous drainage by unconventional
pathway
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51. Clinical importance
• Ciliary body detachment occurs through
supraciliary lamina,
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52. Choroid
• Thin but highly vascular membrane lining the
inner surface of sclera,
• Choroid normally 100-220μm and thickest at
macula 500-1000 μm. Increases with inflammation
• Extends anteriorly from Ora serrata to the optic
nerve posteriorly,
10/16/2023 Mlaluko MD 52

53. Cont…
• Becomes continuous with pia and arachnoid
at the optic nerve,
• Internal face is concave and accommodates the
retina with no adherence while the external is
convex, solidarized with sclera through the
ciliary nerves, vessels and the lax connective
tissue.
10/16/2023 Mlaluko MD 53

54. Choroidal physiology
The choroidal circulation is responsible for
about 85% of the blood flow in the eye. Some
other functions are –
• Regulates the temperature of the retina,
• Aids in regulating the pressure in the eye,
• Provides nutrients to macula, retina and optic
nerve,
• It absorbs light and limits reflections in the
eye, which could harm vision
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55. Cont…
• Choroidal blood flow is higher than that of vital
tissues like retina and brain
• Choroidal blood flow ranges from 800-
2000mL/min
• The deterioration of the oxygen flow from the
choroid to retina can cause ARMD. The
choroidal flow of blood can warm and cool the
retina.
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56. Cont…
• Also it comprises secretory cells, which are
likely involved in the modulation of
vascularization and in development of the
sclera.
• In embryogenic, it acts as site for
erythropoiesis
• Fluctuations in the choroidal thickness
moves the retina backwards and forward,
aligning the photoreceptors to the plane of
focus.
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57. Anatomy of choroid
• It divided into layers
Bruch’s membrane,
Layer of choriocapillaris(choriocapillaris; thickest
and most abundant in submacular area),
Choroidal stroma (Sattler and Haller’s layer),
Suprachoroidal lamina (lamina fusca),
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58. Cont…
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59. Cont…
Bruch’s membrane
• Innermost thin and transparent layer of the
choroid. It connective tissue sheet that
separates the retina from the choroid and
supplies oxygen and nutrition to the outer
retina.
• It has five layers
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60. Cont…
1. Basement membrane of RPE
2. Inner collagenous zone
3. Elastic layer
4. Outer collagenous zone
5. Basement membrane of choroidocapillaris
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61. Cont…
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62. Cont…
Choriocapillaris
• is immediately adjacent to Bruch's membrane
and is formed by an anastomotic network
of capillaries.
• These capillaries arise from the arterioles of
Sattler's layer of the choroid.
10/16/2023 Mlaluko MD 62

63. Cont…
• Choriocapillaris provides nourishment to the
RPE and photoreceptors.
• It also filters waste products from the outer
retina and functions in thermoregulation of the
back of the eye.
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64. Cont…
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65. Cont…
Sattler's layer and Haller's layer
• Embedded in choroidal stroma. Haller's layer
is formed of large blood vessels, while Sattler's
layer is composed of smaller arteries and
arterioles.
• Surrounding stroma is formed by collagen,
elastic fibers, fibroblasts, non-muscular
smooth muscle cells and melanocytes, as well
as macrophages, mast cells and lymphocytes.
10/16/2023 Mlaluko MD 65

66. Cont…
Suprachoroid
• Is a transitional zone between the choroid and
adjacent sclera.
• It is composed of collagen fibers, fibroblasts
and melanocytes.
• This thin outer layer contains epithelium lined
spaces which empty into veins and are
thought to play a role in lymphatic drainage
of the eye.
10/16/2023 Mlaluko MD 66

67. Brain retinal barrier (BRB)
It composed of
• Fenestrated endothelium of the
choriocapillaries
• Bruch’s membrane
• RPE
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68. Blood supply to uveal tract
• Arterial supply from branches of ophthalmic
artery
• ACA, LPCA, SPCA
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69. Cont…
Anterior ciliary arteries
• Branches from muscular arteries,
• 2 each except to LR,
• It pierces sclera near limbus and anastomose
LPCA to form major arterial arcades of iris,
• Supplies anterior part of globe around Ora
serrata
10/16/2023 Mlaluko MD 69

70. Cont…
Short posterior ciliary arteries
• 15 to 20 SPCA10 to 20 branchesenter
the sclera in the ring around the optic
nerveanastomose with other branches from
SPCA to form the circle of Zinn (Zinn-Haller)
which encircles the ON at the level of choroid
then run between sclera and choroid to
branch and supply Choroid posterior to the
equator
10/16/2023 Mlaluko MD 70

71. Cont…
Long posterior ciliary arteries
• Two LPCA pierces the sclera. Lateral and
medial to the ring of SPCATo the anterior
globeenters the CB and branches superiorly
and inferiorlyanastomose with each other
and with the ACA to form major arterial
circle of iris
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72. Cont…
• Venous drainageVortex vein
• Lymphatic drainage??
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73. Innervation
Short and long ciliary nerves
• The short ciliary nerves (10 to 20) derive from
the ciliary ganglion, and the two long ciliary
nerves derive from the nasociliary nerve
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74. References
• American Academy of Ophthalmology (AOO
2022/23)
• Wolf’s anatomy
• EyeWiki
• https://www.kenhub.com/en/library/anatomy/c
horoid
• https://byjus.com/neet/choroid
• https://www.ncbi.nlm.nih.gov/pmc/articles
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