detail about uveal anatomy

1. ANATOMY & PHYSIOLOGY OF UVEAL TRACT
Dr.Lhacha Wangd(Resident)
JDWNRH, KGUMSB

2. Outline
• Anatomic classification of uveal track
• Macroanatomy
• Microanatomy
• Physiology of uvea
• Clinical correlates

3. Introduction
The middle vascular layer of eyeball consists of three part-
- iris, ciliary body, choroid
Functions: -Regulates light entry & anchors the lens
-Absorbs reflected light
-Nourishes eye
Walls of eye ball
Middle vascular
layer
Outer Fibrous
layer
Inner nervous
layer
retina
Uveal tract
Sclera & cornea
2. Ciliary
body
1.Iris
Anterior
uvea
3.choroid
Posterior
uvea

4. Embryology
Iris-
• Both the layers of epithelium are derived
from the marginal region of optic
cup(Neuroectoderm)
• Sphincter and dilator derived from anterior
epithelium
• Stroma and vassels- mesoderm
Ciliary body-
• Proximal region of optic cup-
neuroectoderm which undergoes
convulation to form ciliary process(70-75)
Choroid-
• Vascular endothelium and the haemopoietic cells of choroid are
derived from endoderm
• Choroidal stroma ( vascular pericytes, smooth muscles, melanocytes
and collagenous components) of choroid are derived from ectoderm
Iris origin Ciliary body

5. Iris
• Thin, pigmented contractile circular
structure, analogous to the diaphragm of
a camera
• Anterior extension of uveal tract
• Extends from iris root to iris margin that
forms the pupil
– Central aperture is called pupil (3-4mm)
• Lies on anterior lens surface, surrounded
by aqueous humour
• Posteriorly, Central portion of iris is in
contact with lens which give characteristic
conical configuration
• Functions; 1.Regulates light entry
2.Give distinctive eye colour

6. Iris- gross anatomy
• Rough anterior surface & smooth posterior
surface
• Average diameter: 12mm
• Collerate-thickened iris (0.6-1mm) wide
located 2mm from the pupillary margin
• Anteriorly iris divided into two parts by
collarete
1.Inner pupillary zone (1-2mm wide)
2.Outer ciliary zone (3-4mm wide)
Thickness: 0.5mm
• Thickest at collarette
• Thinnest at the root
• Thin regions eg iris root & margin are more susceptible to tearing in injuries
It is attached peripherally to the midline of the anterior surface of ciliary body

7. Iris- Macroscopic appearence
Pupillary zone- 1.6mm wide
• Begins at margin of pupil known as
pupillary ruff( anterior termination of
the iris pigmented epithelium)
• it has lots of
-connecting crest
-deep radial slits/ridges
known as (Fuchs crypts/somates)- due to
radial arrangement of vessels and
connective tissue
Ciliary zone- divided into three area
1. Inner smooth area
2. Middle furrowed area (contraction)
3. Marginal cribriform area ( visible only
in gonioscopy )
crypts
Choroid

8. Iris microanatomy- 4 layers
2.Stroma & sphincter muscle
• Loose, pigmented, highly vascular
connective tissue
• Composed of pigmented & non-
pigmented cells, muscles, collagen
fibrils & extensive ground substance
– Pigmented: melanocytes & clump
cells(Pigmented cell)
– Non-pigmented: fibroblast, lymphocyte,
macrophage, mast cells
3. Anterior epithelium
4. Posterior epithelium
1. Anterior limiting layer-
2. Iris stroma
1. Anterior border layer:
• Thin, discontinuous
(cryptic) condensed
anterior stroma
• Composed of collagen
fibrils & fibroblasts
• It contains contains
number of melanocytes-
regardless of iris color-in
darker iris melanin
granules are dense &
numerous

9. Ctn…
• Color of iris is determined by the character of
melanin and amount of pigmentation not by the
number of melanocytes
• Blue iris is relatively free of pigmentation there
for absorbs long waves of light but reflects
shorter blue wave giving blue color
• Brown iris has abundant stromal pigmentation.
• Benign proliferation of uveal melanocytic cells-
iris nevus
• Malignant transformation of Iris nevus can lead
into iris melenom

10. Iris muscle • Two types of iris muscle located in
the stromal layer of iris.
• Sphincter muscle in pupillary zone
and dilator muscle in the ciliary
zone
Sphincter muscle
• Oriented parallel to the pupillary
margin
• Measure 0.75mm in diameter and
has thickness of 0.1-1.7mm,
• Contractions causes constriction
(Miosis)
• Supplied by parasympathetic nerveDilator muscle
• 4ųm in thickness
• Located in ciliary zone
• Oriented radially from iris root toward the pupil
• Contraction cuase- dilatation of pupil
• Supplied by sympathetic nerve

11. Ctn…
3.Anterior epithelium &
dilator muscle
• Composed of unique
myoepithelial cells
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

12. Iris nerve supply- sphincter muscle
1. Efferent presynaptic
Parasympathetic nerve begins
oculomoter nucleus -Edinger-
Westphal nucleus(EWN) in
midbrain
2. Axons of EWN extends into 111n
(Oculomoter nerve)
3. Leaves at dorsomedial aspects of
brain stem
4. Enters orbit via the inferior
division of 111n
5. Terminates in ciliary ganlion
6. Axons from ciliary ganglion
extends as post synaptic fiber via
short ciliary nerve to innervate
the sphincter pupillae.

13. Parasympathetic innervation of iris

14. Iris nerve- dilator muscle
Sympathetic nerve to dilator muscle
involves three neurons;
1. First(central) neurons- extends from
posterior hypothalamus to terminates
in ciliospinal center of Budge (C8-T2)
3. Third(post-ganglionic)- extends from
cervical ganglion along the internal carotid
artery, enter cavernous sinus and joins
ophthalmic division of trigeminal nerve.
From ciliary ganglion it innervates dilator
muscle via nasociliary and long ciliary
nerve.
2. Second( preganglionic)- axons extends
from ciliospinal centre to superior cervical
ganglion

15. Iris and pupil physiology
• In bright light there
is activation of
parasympathetic
nerve
• In dim light there
is activation of
sympathetic
nerve
• Shining light to an eye cause causes pupillary constriction same- direct light reflex
• Shining light to one eye cause pupillary constriction of other eye- consensual light reflux

16. Pupillary light reflux
Light reflux is mediated by photoreceptors and
subserved by four neurons
1. First(sensory) neurons-connects each retinal
with pretectal nuclei.Axons originating from
the nasal retina cross in the chiasm pass in
opposite optic tract to terminate in
contralateral pretectal nucleus, temporal
axon pass uncrossed to terminate in
ipstilateral pretectal nucleus
2. Second(interneuron)- connects each
pretectal nucleus to both Edinger-Westphal
nuclei
3. Third(preganglionic)- connects EDN with
ciliary ganglion via oculomoter nerve along
with parasympathetic nerve
4. Fourth( post ganglionic)- extends from ciliary
ganglion as short ciliary nerve to sphincter
pupillae

17. Relative affarent pupillary defect (RAPD)
Normally when
light is shine to one
eye it cause
constriction of eye-
dual activation of
parasympathetic
innervation of both
iris
However when light is
shone to disease eye
both eye dilates instead
of constriction (RAPD+)-
due to deactivation of
parasympathetic nerve
as a result of reduced
perception of light

18. CILIARY BODY • It extends from the posterior limit of limbus (
scleral spur & iris root) to Ora serrata
• Its is triangular shape in cross section- base
facing anterior chamber and apex at ora
serrata
• Dimension- 7mm wide temporally
-6mm nasally (from limbus)
It consists two parts
1. Pars plicata-2mm- Anterior vascular part
2. Pars plana- 4mm- Posterior flat avascular
part
Avascular pars plana is located 3-4mm from the corneal limbus which is the safest
posterior surgical approach to the vitreous cavity
Function
1. Aqueous humor production
2. Lens accomodation
3. Facilitates aqueuos drainage

19. Ciliary process
o 70-80 finger-like projections with
vascular core radiating from pars
plicata
– Occupy peripheral part of
posterior chamber
– Each process is about 2mm long
and 0.5mm in diameter
– Ciliary processes increases
surface area for secretion
• Grooves in between serve as
attachment for lens zonules
• Zonules are the suspensory
ligament of lens produced by
ciliary epithelium
• Provide stability of lens and
accommodation

20. Ciliary structure
It consists of three structure;
1.Ciliary epithelium-
a)Nonpigmented(Inner)
b)Pigmented (outer)
2.Srtoma-
vascular layer
3.Muscular layer

21. Epithelium
2. Non-pigmented epithelium(NPE)(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
- cells are interlinked by tight junction called zonulae occludentes
- Diffusion barrier between blood & aquous ( blood aqueous barrier)
Epithelium two layers ;
1.Pigmented epithelium(PE) (outer –
next to stroma)
– Anterior part continuous with
anterior iris epithelium
– Posteriorly it is continuous with
retinal pigment epithelium

22. Structural anatomy- epithelium
• Two layer of epithelial cells of
ciliary body forms a unique
combination
• Bosolateral surface of NPE cells
faces aqueuos humor and
basolateral surface of PE cell
faces towards the stroma
• Apical surfaces of PE and NPE
cells are justaposed with gap
junction
• Two Epithelial cell is considered
functional unit.
• This unique combination of two epithelial cells is important for
secretion aqueous humor

23. Aqueuos humor formation
It involves three essential steps;
1.Uptake of Fluid from the Stroma
a. Na+/H+ counter-exchanger (the NHE-1 antiport)-
intracellulare transport of NaCl is coupled H+ and
HCO3- towards stroma( Bicarbonate is produced by
carbonic anhydrase inhibitors)
b. Na+−K+−2Cl− co-transporter (symport)-NaCl is
transported into the cell via the concentration
gradient. Water follows the solutes via water
spore/aquaporin
2.Fluid Transfer Through Gap Junctions
• Fluid transfer is parallely coupled between PE-NPE
cells due numerous gap junction between them
3.Fluid Transfer into the Aqueous Humor
• Final step is NaCle is actively trasported through the basolateral surface of
NPE cell toward aqueuos via Na+/K+ ATPase
• Water passes pasively via the aquaporin

24. Composition of aqueous humor
• Water- 99.9% of nomal aqueous
• Protein- 5-16/100ml, 1% less than plasma concetration
• Glucose – 75 % of plasma concentration
• Electrolytes
- Na+- similar to plasma
- Cl- ion concetration is high than plasma
-Phosphate- low than plasma concentration
• Ascorbic acid- very high in aqueous
• Various proportion of coagulation and anti coagulation
pathways are present

25. Aqueous flow
1. Produce by ciliary body
2. Passes from PC to AC via pupil
3. About 90% of aqueuos flows
through Trabecular meshwork
which drain through Schlemm
canal to episcleral vein
• 10% of aqueuos drain through
Uveoscleral route across the face
of ciliary body into the
suprachoroidal spaces

26. Ciliary muscle
• 3 groups of smooth muscle fibers which function as unit
1.Longitudinal muscle(Outer)-
• Attached anteriorly to scleral spur,
outer trabecular meshwork
2.Radial muscle/oblique-
• Attached to the inner uveal mesh
work
3.Circular muscle(inner muscle)
• Primarily attached to the ciliary and
iris stroma
Posteriorly muscle are attached to-
elastic structure of par planna vessels
and Bruch’ s elastic

27. Ciliary muscle function
• Ciliary muscle contraction also causes opening of intertrabecular spaces/spore-
facilitates aqueous filtration
• At the accommodation at rest zonules
are in tension which stretch and
flattened the lens
Ciliary Action
a) Contraction muscle causes anterior
movement of ciliary body,
b) Coordinated anterior-inward
squeezing effects- displaces
processes towards the lens equator.
c) Relaxation of zonules on the lens
capsule and lens assumes more
spherical shape,
d) Produces accommadation

28. 3. CHOROID
• 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)
• Functions:
– Nourishment for adjacent retina
– Block light entering through sclera, retain light entering through
pupil

29. Choroid layer
Choroid has three layers-
1. Inner Bruch’s membrane
2. Middle stroma/vascular
layer
3.Suprachoroid-
• Interface/transition zone between choroid and sclera
• Composed of interconnected lamellar fibers that connected
choroid and sclera
• Potential space- may get filled up with blood/fluid in diseased
eye

30. Ctn…
Bruch’s membrane
• Also called lamina vitrea
• Extend from optic nerve head to ora
serrata
• Thin refractile connective tissue
(membrane) between choriocapillaris
(choroid) and RPE (retina)
• Prevents choroid vessels from
penetrating the retina but allows
nutrients, proteins etc
• Constitutes element of both retina and
choroid
Microscopically is composed of;
1.Basement membrane of RPE
2.Inner collagenous layer
3.Elastic tissue layer
4.Outer collagenous layer
5.Basement membrane of choriocapillaris

31. Ctn-
With increasing age although there is atrophy of
choriocapillaris, there is increase in Bruch’s membrane
• Drusen- visible deposits
between RPE basement
membrane and inner layer of
collagenous layer of Bruch’s
membrane

32. Choroidal vasculature
Choroidal circulatiob acounts for
85% of blood circulating through
eye
Choroid receives artery from the
branches of ophthamic artery
It has two arterial system;
1. Anterior arterial system
2. Posterior arterial system
1.Anterior arterial system
• Comprised of muscular artery which
follows there tendenous insertion at
sclera as anterial cilairy artery (ACA)
• There are two ACA in each rectus
muscle except Lateral rectus muscle
which form anterior uveal arterial
arcades at iris

33. Posterior arterial
Posterior ciliary artery branches
several time in orbit giving rise into;
1.Short posterior ciliary artery(SPCA)
• 10-20 cluster of short posterior
ciliary artery(SPCA) perforate sclera
(2-2.5)mm from the optic disc.
• Nasal ciliary artery supplies nasal
quadrant of choroid vise versa
2.long posterior ciliar artery(LPCA)
• LPCA pierce the sclera (3-4) mm
from the optic disc outside the ring
of PSCAs
• Supply choroid, give branches to
choriocapillaries and terminate in
main arterial circle of irs

34. Choriocapillaries
• Mono layers of broad wide capillaries
be the plane of artery and Bruch’s
membrane
• Arterioles and venules join from the
external surface obliquely.
• Choriocapillaries measure 20-50 um in
diameter and appears as a continuous
meshwork of reticulation
Capillaries are flattened
providing large surface are for
metabolic exchanges.
Function
• It supplies oxygen and
nutrients to Bruch’s
membrane and outer third of
retina except in macula.

35. Venous drainage
• Choroid blood are drained by the
four vortex vein;
• 2 superior and 2 inferior vortex vein
• Vortex vein lie (2.5-3.5)mm posterior
to the equator
• Vertex vein are closely related to IO
and SO muscle
• Superior and two inferior
vortex vein drainins to
superior and inferior orbital
vein respectively

36. Choroidal stroma
Stromal structures
1. Blood Vessels are the
main constituent of
choroid stroma
2. It has ramdomly oriented
collagen fibers
3. Cells-Pigmented cells-Numerous melanocytes- produces pigmented
melanin granules- absorbs scattered light
Non pigmented cells
• Fibroblas cells- produce collegen
• Macrophages,
• Plasma cells. Lymphocytes, mast cell-
4. Ground substances- water and mucinous substance of unknown
origin

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