detailed

1. Anatomy and Aplied anatomy of
Uvea
Presenter : Dr. Darshan S M
Moderator : Dr. K Kanthamani

2. • Uvea is the middle vascular coat of eye ball.
• From anterior to posterior, the uvea or uveal
tract can be divided into three parts
- Iris,
- Ciliary body
- choroid.

3. • The name “uvea” has originated from Latin
word grape.
• Why a grape ?
If the stem is removed from a grape, the hole
looks like the pupil and the grape the eyeball.

4. Iris
• Iris is the anterior most part of the uveal tract.
It is a thin and circular structure which forms a
diaphragm like structure in front of the
crystalline lens.
• The word “iris” has originated from a Greek
word. In Greek mythology the iris is the name
of Greek goddess of rainbow -

5. • The diaphragm formed by iris contains a
central aperture known as pupil.
• The location of the pupil is not exactly central,
its little nasal to the center. The pupil
determines the amount of light entering the
eye.
• The normal size of pupillary aperture is
3-4mm.

7. • Iris is attached to the middle of anterior
surface of ciliary body.
• The iris divides the space in front of the lens
into anterior chamber and posterior chamber.

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

10. • Anterior surface of the iris is divided into a
pupillary zone and a ciliary zone by a circular
ridge, located 1.5 mm away from pupillary
margin, called collarette
• also known as iris frill.

11. Aplied anatomy
• During blunt trauma, damage to iris occurs
most commonly at the iris root, where the iris
rips away from the ciliary body

12. • Anterior surface of the iris is divided into a
pupillary zone and a ciliary zone by a circular
ridge, located 1.5 mm away from pupillary
margin, called collarette (also known as iris
frill).

13. Aplied anatomy
• Collarette is the site of foetal pupillary
membrane attachment

14. Pupillary Zone
• Pupillary zone extends from pupillary margin
to collarette.
• Pupillary zone is relatively flat.
• Pupillary margin is marked by a dark border,
known as pupillary ruff.
• Pupillary ruff is the anterior termination of
the pigmented layer.

15. Ciliary Zone
• Ciliary zone of iris extends from 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 iris

17. Aplied anatomy
• In laser iridotomy, the opening is created in
areas of iris crypts, as it requires less amount
of energy in these thinnest areas of iris
thickness.

18. Microscopic structure of Iris
1. Anterior limiting layer
• Anterior limiting layer lines the iris and is the
anterior most condensations of iris stroma.
• The layer consist of mainly fibroblasts and
melanocytes.
• These cells are arranged in a meshwork
• -fibroblasts are located on the surface and
melanocyte beneath them.

19. • The colour of iris depends on the thickness of
the layer and melanocyte dispersed in anterior
limiting layer.
• The color of the iris is largely determined by
three main variables:
(1) the density and structure of the iris stroma,
(2) the pigment epithelium and
(3) the pigment content (granules) within the
melanocytes of the iris stroma

20. • Heterochromia of iris (Greek: heteros 'different'
+ chroma 'color'):
• it is of two kinds.
• In complete heterochromia, one iris is a different
color from the other.
• In partial heterochromia or sectoral
heterochromia, part of one iris is a different color
from its remainder.

21. Aplied anatomy
• Neovascularisation of iris occurs in anterior
limiting layer.

22. 2. Iris stroma
• Iris stroma forms the main bulk of iris tissue
and contains sphincter pupillae, dilator
pupillae muscles, vessels and nerves
• Cells in iris stroma:
• Pigmented cells = melanocytes + clump cells
• Non-pigmented cells = fibroblasts +
lymphocytes + macrophages + mast cells

24. Aplied anatomy
• Pigment dispersion syndrome
• It is a bilateral condition characterized by the
liberation of pigment granules from the iris
pigment epithelium.
• It Is caused by the mechanical rubbing of the
posterior pigment layer of the iris against lens
zonules as a result of excessive posterior
bowing of the mid-peripheral portion of the iris.
• sometimes pigment epithelium itself may be
abnormally susceptible to pigment shedding.

26. Muscles in iris stroma:
• The sphincter pupillae muscle is a circular muscle,
• 0.75 to 1 mm wide, composed of smooth-muscle cells.
• The muscle is 0.1 to 1.7 mm in thickness and is
considerably thicker than the dilator papillae.
• It encircles the pupil and is located in the pupillary zone
of the stroma.
• The sphincter muscle is firmly adherent to the
surrounding stroma of iris.
• Sphincter muscle is composed of spindle-shaped cells
that are oriented parallel to the pupillary margin so
contraction of the sphincter causes the pupil to constrict
(a process known as miosis).
• The muscle is innervated by the parasympathetic system.

27. Aplied anatomy
• the sphincter pupillae retains its function even
if severed radially because of its unique
distribution of fibres.

28. • the dilator pupillae muscle extends from the iris
root to a point in the stroma below the
midpoint of the sphincter.
• A dense band of connective tissue separates the
sphincter and dilator muscles from each other.
• Because of the radial arrangement of the fibres
of the muscle, contraction of the dilator pupillae
muscle pulls the pupillary
portion toward the root, thereby enlarging
the the size of pupil ( a process ka mydriasis).
• The dilator pupillae muscle is sympathetically
innervated.

29. Blood vessels in iris stroma:
• The iris arteries are branches of major circle of the
iris, located in the ciliary body near the iris root.
• The iris vessels usually follow a radial course from the
iris root to the pupil margin.
• These vessels are surrounded by a dense network of
collagenous fibrils which is embedded in to the
collagen network of the stroma.
• Such arrangement of collagen network prevents the
iris vessels from
kinking and compression during the extensive iris
movement during constriction and dilatation of
pupil.
• Iris veins have very thin walls consisting of
endothelium surrounded by a thin layer of collagen

30. Ciliary body
• Ciliary body is the middle part of the uveal tract . It is a
ring shaped structure which projects posteriorly from
the scleral spur.
• It is brown in colour due to melanin pigment.
• Anteriorly it is confluent with the periphery of the iris
(iris root) and anterior part of the ciliary body bounds a
part of the anterior chamber angle.
• Posteriorly ciliary body has a crenated periphery,
known as ora serrata, where it is continuous with the
choroid and retina.
• Ciliary body has a width of approximately 5.9 mm on
the nasal side and 6.7 mm on the temporal side.

31. Parts of ciliary body
• Ciliary body, in cross section, is a triangular
structure .
• Outer side of the triangle (O) is attached with the
sclera with suprachoroidal space in between.
• Anterior side of the triangle (A) forms part of the
anterior & posterior chamber. In its middle, the iris
is attached.
• The inner side of the triangle (I) is divided into two
parts. The anterior part (2 mm) with finger like
processes is known as pars plicata (corona ciliaris)
and posterior smooth (4 mm) is known as pars
plana (orbicularis ciliaris).

33. Pars plicata:
• The pars plicata is the portion of ciliary body
which contains the ciliary processes.
• Ciliary processes are the finger like projections ,
which extend into the posterior chamber.
• The regions between ciliary processes are called
valleys of Kuhnt.
• They are approximately 70 to 80 in numbers.
• A ciliary process measures approximately 2
mm in length, 0.5 mm in width, and 1 mm in
height.

34. Pars plana
• Pars plana is the flat or
smooth part of the ciliary body.
• It terminates at the ora serrata, which is the
transitional zone between ciliary body and
choroid.
• Histologically, the pars plana consists of a double
layer of epithelial cells: the inner, nonpigmented
epithelium, which is continuous with
neurosensory retina
• and the outer, pigmented epithelium, which is
continuous with the retinal pigment epithelium
(RPE) .

35. Aplied anatomy
• The pars plana is a relatively avascular zone,
which is important surgically in the pars plana
approach to the vitreous space.
• The pars plana provides surgical access to the
vitreous and retina

36. Ora serrata: the transition zone
• The ora serrata can be termed as the anterior
border of the neurosensory retina
• Aplied anatomy
Topographically, ora serrata corresponds to the
insertion of the medial and lateral rectus
muscles.

37. Lens and ciliary body:
• The zonules course from ciliary body to the
lens.
• Some of these zonular fibers insert into the
internal limiting membrane of the pars plana
region and travel forward through the valleys
(valleys of Kuhnt) between the ciliary
processes

38. Layers of ciliary body:
• From inside to outside (from sclerad to vitread), ciliary
body consists of following four layers.
• 1. Ciliary epithelium:
• 1A . Non pigmented epithelium of ciliary body NPE of
ciliary body extends from iris root to ora serrata.
• It begins as a continuation of posterior pigmented
epithelium of iris near iris root.
• At ora serrata, the NPE continues as sensory retina.
• It gives origin to parts of the suspensory lens ligament.

39. • 1 B. Pigmented epithelium of ciliary body:
• The cells of the pigmented epithelium are 8 to 10
micro meter wide and contain large pigment
granules.
• These pigment granules are three to four times
larger than those of the choroid and retina.
• These cells are rich in organelles and are very
active metabolically .
•
The cells of pigment epithelium secretes basement
membrane which continues posteriorly with
the retinal pigment epithelium (RPE).

40. Aplied anatomy
• Ciliary epithelium : metabolic activity
• The cells of both the ciliary epithelium have a
greater number of mitochondria and thus
they have a higher degree of metabolic
activity, with a significant role in the active
secretion of aqueous humor.

41. 2. Ciliary stroma:
• Ciliary stroma contains blood vessels, nerves
and ciliary muscle.
• Ciliary stroma continues anteriorly with iris
stroma and continues posteriorly with
choroidal stroma after thinning out at pars
plana

42. • Blood vessels in ciliary stroma: Major arterial circle
of iris
• Major arterial circle of iris, formed by the
anastomosis of long posterior ciliary arteries and
anterior ciliary arteries , is located in ciliary stroma
near iris root just in front of circular portion of
ciliary muscle.
• Ciliary stroma also consists of numerous capillaries
which are fenestrated and large in size.
• The capillaries are more in numbers in ciliary
processes, making them the most vascular organ of
the eye

43. Muscle in ciliary stroma: ciliary muscle
• Ciliary muscle is a nonstriated or smooth
muscle primarily situated in the anterior two
thirds of the ciliary body stroma. The muscle
has three parts –
> Outer longitudinal (Brücke's muscle)
> Middle oblique portion (also called reticular
or radial)
> inner circular portion (Müller's muscle)

44. • Contraction of the ciliary muscle, especially of
the longitudinal and circular fibers, pulls the
ciliary body forward during accommodation.
• This forward movement of ciliary body
relieves the tension in the suspensory lens
ligament (zonules), making the elastic lens
more convex and there by helps the eye in
accommodation by increasing the refractive
power of the lens

45. • Ciliary muscle is innervated by the autonomic
nervous system, parasympathetic
postganglionic fibres derived from the
oculomotor nerve.
• The nerve fibres reaches the muscle via short
ciliary nerve.
• The parasympathetic stimulation activates the
muscle for contraction, whereas sympthetic
innervation likely has an inhibitory effect.

46. Supraciliary lamina:
• supraciliary lamina is the outermost layer of
ciliary body which lies adjacent to the sclera.
• Because of the lamellar arrangement of
connective tissue in this area, supra ciliary
lamina acts as a potential space.
• Thus it also helps aqueous humor to exit by
the unconventional pathway .

47. Aplied anatomy
• Ciliary body detachment occurs through
supraciliary lamina

48. Ciliary process :
• Ciliary processes are finger like projections seen
in pars plicata of ciliary body.
• Ciliary processes are approximately 70 to 80 in
numbers in each eye and extend into the
posterior chamber, and the regions between
these ciliary processes are called valleys of Kuhnt.
• Zonules of lens (suspensory ligaments of lens) are
inserted in these valleys.
• The ciliary processes are white whereas the
valleys of Kuhnt are dark in colour.

49. • Ciliary processes increase the surface area of
pars plicata, which is approximately 6 square
centimetre, approximately five times the
surface area of corneal endothelium

50. Blood supply of ciliary process:
• Long posterior ciliary artery, a branch of
ophthalmic artery, pierce the globe near the
optic nerve and run up to ciliary body to form
major arterial circle.
• Several branches from major arterial circle
supply ciliary processes.
• These are mainly pre capillary arterioles and
they divide in to network of capillary plexuses
in each of the ciliary processes.
• These vessels drain in to choroidal and
intrascleral veins

51. Aplied anatomy
• The pre capillary arterioles supplying the
ciliary processes have sphincters which may
be responsible for the auto regulation of
blood supply to the tissue.

52. Choroid
• Choroid is a thin but highly vascular
membrane lining the inner surface of sclera.
• It extends from anteriorly ora serrata to the
optic nerve posteriorly.
• Choroid becomes continuous with pia and
arachnoid at the optic nerve.
• Choroid is normally 100-220 µm thick ;
thickness is highest at macula 500- 1000 µm.

53. Aplied anatomy
• Choroidal thickness increases in intraocular
inflammation.

54. • Choroid can be divided into the following
layers histologically
• 1. Suprachoroid lamina (lamina fusca):
• 2. Choroidal stroma:
• 3. Layer of Choriocapillaris (Choriocapillaries
are thickest and most abundant in submacular
area )

55. Aplied anatomy
• choroidal circulation:
• Choroidal circulation constitutes 85% of the
blood circulation of the eye.
• Choroidal blood flow is higher than that in
tissues like retina and brain.
• Choroidal blood-flow ranges from 800 to 2000
mL/min/100 g of tissue.
• In embryonic life, choroid serves as an
additional site for the erythropoiesis.

56. 4. Bruch's membrane:
• Bruch's membrane is the innermost layer of
choroid
• Bruch's membrane is composed of 5 layers
and from internal to external,
• these are

58. Aplied anatomy
• Outer blood–retinal barrier
The outer blood–retina barrier (BRB) is
composed of three structural entities,
> the fenestrated endothelium of the
choriocapillaris,
> Bruch's membrane and
> the retinal pigment epithelium (RPE).

59. Blood supply of uveal tract:
• The blood supply of the uveal tract is mainly
from three arteries namely short posterior
ciliary arteries, long posterior ciliary arteries
and anterior ciliary arteries.
The posterior ciliary arteries are branches of
the ophthalmic artery.

60. SHORT POSTERIOR CILIARY ARTERIES
• 15 to 20 short posterior ciliary arteries arise →
form 10 to 20 branches → enter the sclera in a
ring around the optic nerve → anastomose with
other branches from the short posterior ciliary
arteries to form the circle of Zinn (Zinn-Haller)
which encircles the optic nerve at the level of the
choroid → they run in suprachoroidal space
between sclera and choroid, branch and
• supply the choroid.

61. LONG POSTERIOR CILIARY ARTERIES
• two long posterior ciliary arteries enter the
sclera: one lateral and one medial to the ring
of short ciliary arteries → run between the
sclera and the choroid to the anterior globe →
enter the ciliary body and branch superiorly
and inferiorly → anastomose with each other
and with the anterior ciliary arteries to form a
circular blood vessel,
• the major arterial circle of the iris

62. ANTERIOR CILIARY ARTERIES :
• 7 anterior ciliary arteries are derived from
muscular branches of ophthalmic artery
• two each from arteries of superior rectus,
medial rectus, inferior rectus and only one
from lateral rectus muscle → reaches
episclera, form plexus and give branches →
pierce sclera near the limbus to enter the eye
→ anastomoses with long posterior ciliary
arteies to form major arterial circle of iris

63. • Thank you !!