a presentation on anatomy of uveal tract of eye

1. UVEAL TRACT
ANATOMY
DR. RIFAT BINTH REZAYEE
PHASE-A
COMMUNITY
OPHTHALMOLOGY
BSMMU

2. INTRODUCTION
 ‘Uvea’ derived from the Latin word ‘Uva’ means
grape. On dissection the whole structure is brown
and spherical and resembles a grape & the optic
nerve forming stalk so it is named as such.
 The middle vascular coat of eyeball.
 Analogous to the vascular pia arachnoid of the
brain

3. INTRODUCTION
 Developmentally, structurally and functionally one
indivisible structure.
 Consists of three components forming a continuous
structure:
- CHOROID
- CILIARY BODY
- IRIS

4. ATTACHMENT
 Uvea is firmly attached to
following sites:
- Scleral spur
- Exit points of the vortex vein
- Optic nerve

5. EMBRYOLOGY
 Developes from a combination of
mesoderm and neural crest cells
 Corresponding epithelial layers of the
ciliary body and iris are derived from
the neuroectoderm.
 Uvea obtains its dark color from neural
crest derived melanocytes residing
within it.
 Blood vessels and ciliary muscles are
derived from the mesoderm.

6. Choroid :
By condensations of neural crest
cells and mesoderm surrounding
the optic cup produces choroid on
the inner aspect of cup.
Choriocapillaris are formed as
fenestrated initially at 2nd month of
gestation then outer layer of large
vessels formed by giving rise to
vortex veins and branches of
posterior ciliary circulation at 4th
month
EMBRYOLOGY ( CONTD….)

7.  Ciliary body and Iris:
 Commences on 11-12th
weeks of gestations.
 after proliferation of
surruonding mesoderm at
the anterior aspect of optic
cup neuroectoderm being
pushed inward and centrally
between the corneal
endothelium and anterior
lens surface and give rise to
ciliary body and iris
epithelium.
EMBRYOLOGY ( CONTD….)

9. EMBRYOLOGY ( CONTD….)

10. 9th week of gestations Ciliary body begins to
appear
12th week of gestations Sphincter pupillae appears
4th month Ciliary process fully formed
5th month Iris and choroid are formed
6th month Dilator muscles begin to
form
Sphincter muscle fully
differentiated
EMBRYOLOGY ( CONTD….)
MILESTONES

11. CHOROID
 The posterior portion of uvea
which nourishes the outer
portion of retina.
 Thickness is .25 mm(thickest
posteriorly and thinnest
anteriorly)
 Extends from optic disc margin
to ciliary body.
 Thin soft brown coat and
extremely vascular.

12. CHOROID ( CONTD…)
 Inner surface smooth and
outer surface rough.
 Perichoroidal space:
 the potential space between
the sclera and choroid.
 Supra choroidal lamina:
 thin pigmented sheet of
connective tissue running
across the perichoroidal
space.

13.  Histologically Three layers
of choroid:
-The vessel layer
-Capillary layer
-Bruchs membrane
 Layers of vessels of
choroid:
-Innermost layer of
choriocapillaries
-Middle layer of small
vessels(Sattler’s layer)
-Outer layer of large
vessels(Haller’s layer)
CHOROID ( CONTD…)

14. The vessel layer:
 It is an External layer consists of
loose connective tissues subdivided
into
 Inner layer of intermediate sized
vessels known as sattler’s layer
 Outer layer of large vessels known as
Haller’s layer
 The arteries are branch of the short
posterior ciliary arteries and extends
anteriorly .but the veins are much
larger and converge to join 4-5
vorticose vein that pierce the sclera
to join the ophthalmic veins.
CHOROID ( CONTD…)

15. The capillary layer:
o It’s the middle layer consists of a
network of wide bore fenestrated
capilleries.
o The bore and densities of
capilleries are greatest at macula.
o The capilleries are supported by
delicate connective tissues
containing melanocytes.
o They are fed by arteries from
vessel layer and drained by veins
into the vessel layer.
CHOROID ( CONTD…)

16. Bruch’s membrane (lamina vitrea):
 Inner homogenous modified
connective tissue layer
histologically appears as an
acellular glassy membrane
beneath the RPE.
 Thickness is 2-4 micrometer
 Consists of following 5 layers:
- The basement membrane of RPE
- Inner layer of collagen fibrils
- A meshwork of elastic fibers
- Outer layer of collagen fibrils
-Basement membrane of
endothelium of capillaries
CHOROID ( CONTD…)

17. Blood supply:
 Mainly from posterior ciliary
arteries
 Recurrent branches from
anterior ciliary arteries
Branches of
ophthalmic
artery
Venous drainage:
vorticose veins drain the choroid and pierce the
sclera to join the ophthalmic veins
Nerve supply:
Sensory and sympathetic by Long ciliary nerve is
the branch of nasociliary nerve which is the branch
of ophthalmic division of trigeminal nerve
Parasympathetic by short ciliary nerves from ciliary
ganglion.
CHOROID ( CONTD…)

18.  Nourish the outer layer of retina by its blood vessels
 The large number of pigment cells absorb excess light that
penitrates the retina thus prevents reflection.
 Changes in blood flow in the choroidal circulation may serve
to produce heat exchange from the retina.
 Assists in regulating intraocular pressure.
 Serves to conduct many blood vessels forward to the
anterior regions of the eye.
Functions:
CHOROID ( CONTD…)

19. CILIARY BODY
 Triangular in cross section,bridges
the anterior and posterior segments
of the eye.
 Apex is directed posteriorly towards
the ora serrata.base is attached to
the sclera via its longitudinal muscle
fibers at its insertion to scleral spur.
 Base give rise to iris.
 Diameter is 5-6 mm as a wide ring of
tissue.

20. CILIARY BODY (CONTD…)
 Two zones:
Pars plicata:
- anterior surface or base is ridged or plicated.
- Richly vascularized.
- Surrounds the periphery of iris and give rise to ciliary
processes
Pars plana :
- posterior surface is smooth,avascular,pigmented
zone.
-The zonular fibers of lens attach primarily in the
valleys of the ciliary processes also along the pars
plana.

21. Two layers of epithelial cells:
 Inner nonpigmented ciliary epithelium facing posterior
chamber.having tight junctions maintaining blood aqueous
barrier.
 Outer pigmented ciliary epithelium which is thick and
more homogenous.
Both the layers are oriented apex to apex and fused by a
complex system of junctions and cellular interdigitations.
CILIARY BODY (CONTD…)

22.  Pigmented epithelium uniform and each of its cuboidal cells has
multiple basal infoldings,a large nucleus,mitochondria and an
extensive endoplasmic reticulum and many malanosomes.
 Non pigmented epithelium is cuboidal in pars plana but columner
in pars plicata.They also have mitochondria large nuclei and basal
infoldings.
 Golgi complex and endoplasmic reticulum are important for
aqueous humor production.
CILIARY BODY (CONTD…)

24. Ciliary muscle ( Three Layers):
 Longitudinal-outer and closes
to scleral spur
 Radial-in the midportion
 Circular-innermost,run around
like an sphinter ,lie close to
the peripheral edge of lens.
CILIARY BODY (CONTD…)

25. Ultra Structurally:
- Multiple myofibrils
- Electron dense attachment bodies
- Mitochondria
- Glycogen particles
- Prominent nucleus.
Innervation:
- postganglionic parasympathetic fibers derived from
occulomotor nerve reach the muscle via short ciliary nerve.
- 97% fibers directed to ciliary muscles for accomodation
- 3%directed to the iris sphincter.
CILIARY BODY (CONTD…)

26. Ciliary stroma:
- Consists of bundles of loose connective tissue
- Rich in blood vessels, melanocytes,containing the embedded
ciliary muscle.
- Connective tissue extend into the ciliary process forms a
connective tissue core.
- The blood vessels consists of the ciliary arteries , veins ,and
capillary networks.
CILIARY BODY (CONTD…)

27. Blood supply:
 Long posterior ciliary artery forming a major arterial arcade in
peripheral edge of iris.
Functions:
 Concerned with the suspension of the lens .
 Help the process of accomodation.
 Anterior surface of the ciliary process produces aqueous humor.
 Posterior surface faces the vitreous and secrets glycos aminoglycans
onto the body.
CILIARY BODY (CONTD…)

28. o Most anterior extension of uvea.
o Thin ,contractile,pigmented diaphragm
with a central aperture called pupil.
o Suspended in coronal plane anterior to
lens and ciliary body in the aqueous
humor.
o Diameter: is 12mm with a
circumference of 37 mm.thickest in
pupillary margin and thinnest in ciliary
margin .
o Color: varies from light blue to dark
brown.
o Divides the space between lens and
cornea into anterior and posterior
chamber.
IRIS

29. Major structures:
 Anterior border or surface: a circular
ridge named the collarette divided the
layer into - central pupilary zone
-peripheral ciliary zone
Central pupillary zone
 Begins at margin of pupil known as
pupillary ruff (anterior termination of
the iris pigmented epithelium)
 Have lots of connecting crest and deep
radial streak known as fuchs crypts
due to radial arrangement of vessels
and connective tissue.
IRIS (CONTD…)

30. Peripheral ciliary zone ( Three areas):
- Inner smooth area
- Middle furrowed or contracted area
- Marginal cribriform area.
Stroma
- Anteriorly devoid of epithelium and has a velvety
appearance.
- Composed of melanocytes, nonpigmented cells, collagen
fibers and a matrix containing hyaluronic acid.
- Aqueous humor flows freely within this loose stroma
IRIS (CONTD…)

31. IRIS (CONTD…)
Sphincter pupillae Dilator pupillae
Muscle fiber Circular smooth
muscle
Radial smooth
muscle
Location Pupillary Margin Ciliary zone
Diameter 1mm 50 -60 micro M
Thickness 1 mm 4micro m
Contraction Contracts pupil Dilated pupil
Nerve Supply Parasympathetic
supply by short
ciliary nerve.
Postganglionic
fibers of superior
cervical
sympathetic
ganglia via the long
Muscles of Stroma

32. Posterior pigmented epithelium:
 Also known as iris pigment
epithelium.
 Densely pigmented and appears
velvety smooth and uniform.
 At posterior continuous with inner
nonpigmented epithelial layer of
ciliary body
 Curled to anterior surface at
pupillary margin known as
pupillary ruff
IRIS (CONTD…)

33. Blood supply of iris:
By major arterial circle provided by radial vessels in iris stroma.
The circle formed by:
2 long posterior ciliary artery and 7 anterior ciliary artery
Minor arterial circle is on collarette.
Radial veins converge and drain into vorticose vein,others follow
arteries forms a corresponding minor venous circle.
Significance of blood supply of iris: all the endothelial lining of
blood vessels including capilleries are non fenestrated and have
tight junctions,making less permeable and forms an important
componant of blood ocular barrier.
IRIS (CONTD…)

34. IRIS (CONTD…)
Blood supply of iris

35. Nerve supply:
Sensory and autonomic supply by long and short ciliary
nerve which are branches of nasociliary nerve which is the
branch ophthalmic division of trigeminal nerve.
IRIS (CONTD…)
Functions :
- Regulate the amount of light enter into eye.
- Responsible for distinctive eye color.
- Eicosanoids are synthesized in iris and ciliary body as
well.
- Pupil movements are mediated by iris muscles.

36. CLINICAL NOTES
Supraciliary space:
a potential space located below the sclera and above the choroid
and ciliary body .this space can expands to accommodate fluid
(delivery of drugs) or microstents (as in minimally invasive
glaucoma surgery)
Circulatory Metastasis:
As being highly vascularized uveal tract is commonly involved in
other general systemic diseases and may be a site of circulatory
metastasis.
Atrophy & Destruction of Retina:
A lesion in choroid may interfere with nutrition to the adjacent
retina causing atrophy or destruction as being provider of
nourishment of it

37. CLINICAL NOTES (CONTD…)
Aniridia:
A rare autosomal dominant disorder where there is an
apparent absence of iris. It is ocurred by mutations of pax6
gene.
Senile changes in Choroid:
Age related changes in Bruch’s membrane lead to areas of
diffuse or discrete thickening known as DRUSEN.
Malignant melanoma of Uveal Tract:
Arise from melanocytes of ciliary body, choroid, iris. They
are the most common malignant intraocular tumor.

38. Heterochromia Iridis:
Iris of one eye or one sector is different from other.
Congenital Coloboma:
A notched defect in iris, ciliary body and choroid or retina.
Oculocutaneous Albinism:
Loss of melanine production within the RPE and
melanocytes within the choroid and iris occur in patients
with ocular & oculocutaneous albinism.
CLINICAL NOTES (CONTD…)

39. Uveitis: Inflammation of iris , ciliary body and choroid.
- Anterior uveitis: consists of iritis , iridocyclitis,cyclitis.
- Intermediate uveitis: inflammation of pars plana upto
peripheral part of retina underlying choroid known as pars
planaitis.
- Posterior uveitis: inflammation of choroid including retina
known as chorioretinitis.
- Panuveitis: inflammation of whole tract.
Iris adhesion: adhesions of iris with lens and other ocular structures
following iritis or uveitis is known as synechiae.
- Anterior synechiae: adhesions to iris with endothelium and
trabecular meshwork.
- Posterior synechiae;iris adheres to anterior lens capsule at
pupillary margin.
CLINICAL NOTES (CONTD…)

40. Iridodialysis: iris thinnest at its root and tear away easily from ciliary
body during blunt trauma to eye.
Pars plana is surgically important due to its avascularity and
position anterior to retina.incisions through sclera and choroid made
in this point into vitreous to prevent haemorhage and RD’
CLINICAL NOTES (CONTD…)