2. Introduction
• Uveal tract is middle vascular coat of the eyeball
• Anterior to posterior is divided into 3 parts-
1. iris- the anterior most part
2. Ciliary body-
3. choriod – the posterior most part
• Iris is responsible for the colour of the eye
• Ciliary muscle plays important role in
accommodation.
• Choriod the very reach vascular support.
3. Functions
The uvea also has secretary & mechanical functions
including production of aqueous humor, improvement
of aqueous outflow and control to near
accommodation.
The primary function of the uveal tract is to supply
nutrition to the eye, both in the health and in disease.
Essentially vascular, the uveal tract provides
sustenance to
- retinal rods and cones through the choriocapillaries
- lens through the aqueous.
4. Iris
• Avg diameter- 12mm, thickness-0.5mm
• Forms diaphragm of lens called pupil.
At center- pupil (which regulates the amount
of light reaching the retina)
At Periperhy- Ciliary body.
• It divides the space between cornea and lens
into anterior and posterior chambers.
5.
6. Macroscopic Appearance
Consists of two surface
Iris has rough anterior and smooth posterior surface.
1. Anterior surface- can be divided into 2 zones by a zigzag line called
collarette.
Ciliary zone- it presents radial streaks due to underyling blood vessesls
Crypts which are depressions where superficial layer of iris is missing
crypts are arranged in 2 rows: the peripheral near the iris &
central near the collarette.
Pupillary zone: lies betweene the collarette and pigmented pupillary
frill/ruff(anterior termination of iris pigmented epithelium) and is
relatively smooth and flat.
7. 2. Posterior surface- Dark brown/ black
Contains-
A. Schwalbe’s contraction folds- 1mm from pupillary border, little radial furrows.
B. Schwalbe’s structural furrowa- 1.5 mm from pupillary border. Narrow and deep
to start with and become wide and shallow as they approach ciliary margin.
C. Circular furrows- finer than radail furrows. Crosses structural furrows at regular
intervals. More marked near the pupil and formed due to difference in thickness
of pigmented epithelium.
8. Microscopic structure
Iris consists of four layers from anterior to posterior
1. Anterior limiting layer-
Consists of melanocytes & fibroblasts, previously called endothelial layer.
The defective colour of iris depends on this layer.
Blue iris- thin layer and few pigmented cells.
Brown iris- thick and densely pigmented.
2. Iris stroma-
Forms main bulk
Consists of collagenous tissue with mucopolysaccharide, lymphocytes, fibroblast and
macrophages.
Structures embeded :
Sphincter pupillae muscle- 1mm broad circular band in pupillary area derived from ectoderm
supplied by parasympathetic fibres by 3rd nerve
It constricts pupil.
9. Cont..
Dilator pupilae muscle- lies in posterior part of ciliary zone
Supplied by cervical sympathetics
dilates the pupil.
3. Anterior epithelial layer-
Is the anterior continuation of pigmented epithelium of retina and ciliary body.
Gives rise to dilator pupillae muscle.
Lacks melanocytes.
4. Posterior pigmented epithelial layer-
Anterior continuation of non-pigmented epithelium of ciliary body.
Derived from internal layer of optic cup
Forms pigmented frill
10. FUNCTIONS OF IRIS
• Controls amount of light entering the eye through
pupil.
• Defines eye colour.
• Control depth of filed.
• Source of blood ocular to tissues.
11. CILIARY BODY
• Forward continuation of choroid at ora serrata.
• Triangular in cut section, the anterior side of the triangle forms the
part of the angle of anterior & posterior chambers.
• In middle attached to iris.
• Outer side- lies against sclera with a suprachoroidal space in
between.
• Inner side- divided into 2 parts
1. Anterior part- ciliary processes called pars plicata about 2mm.
2. Posterior part- smooth part called pars plana about 4mm temporally
and 3mm nasally.
12. Microscopic structure
(From without inwards consists of 5layers)
1. Supraciliary lamina- outermost part
consists of pigmented collagen fibres.
posteriorly continuation of suprachoroidal lamina, ant. Continuous
with anterior limiting membrane.
2. Stroma-
Consists of connective tissue of collagen and fibroblasts.
Ciliary muscle- non- striated, trinagular in cut section, having 3 parts
i. Longitudnal/meridional fibres- origin from scleral spur, inserts
into suprachorodial lamina. Helps in aqueous outflow.
ii. Circular fibres- helps in accommodation (in inner portion, nearest
to lens)
iii. Radial/Oblique fibres- act same as longitudinal fibres.
13. Cont..
3. Layer of pigmented epithelium-
Forward continuation of retinal pigmented epithelium(RPE).
Anteriorly continues with anterior epithelium of iris.
4. Layer of non pigmented epithelium-
Forward continuation of sensory retina.
Anteriorly continues as the posterior pigmented epithelium of iris.
5. Internal limiting membrane-
Forward continuation of internal limiting membrane of retina.
It lines the nonpigmented epithelial layer.
14. Ciliary processes
• Finger like projections from pars plicata
• 70-80 in number, 2mm long 0.5mm diameter
• Site of aqueous production.
• White in colour.
Ultrastructure
1. Network of capillaries- In centre has endothelium with fenestrae.
2. Stroma of ciliary processes- Thin, separates capillaries from epithelium.
3. Epithelium- Two layered with apical apposition.
- Core of processes contains blood vessels and loose connective tissue.
15. FUNCTIONS OF CILIARY BODY
• Formation of aqueous humour.
• Maintenance of IOP.
• Constitutes of blood aqueous barrier.
• Ciliary muscles helps in accommodation.
16. CHOROID
• Posterior most part
• It extends from optic disc to ora serrata.
• Inner surface- Smooth, brown and lies in contact
with pigmented epithelium of retina.
• Outer surface- Rough and lies in contact with sclera.
• Thickness- Posteriorly 0.22mm
Anteriorly 0.10mm
17. Microscopic structure
(From without inwards consists of 3 layers)
1. Suprachoroidal lamina-
-Thin layer, continues anteriorly with supraciliary lamina of ciliary
body.
-Suprachoroidal space- Contains long and short posterior cilliary
arteries and nerves.
2. Stroma-
-It consists of loose collagenous tissue with some elastic and
reticulum fibres, also contains pigment cells and plasma cells.
- Its main bulk is formed by vessels which are arranged in 3 layers:
1) layer of large vessels(Hailer’s layer)
2) Layer of medium vessels (Sattler’s layer) and
3) Layer of choriocapillaris – Rich capilary network which nourishes
the outer layers of the retina.
18. Cont..
3. Basal lamina-
-Also called Bruch’s membrane.
-It lies in approximation with pigment epithelium of
the retina
-Electron microscopy- basement membrane of RPE,
inner collagen, middle elastic , outer collagen and
basement membrane choriocapillaries.
19. FUNCTIONS OF CHOROID
• Blood supply to outer layers of retina
• Assist in the control of intraocular pressure
• Pigment absorbs excess light, avoiding
reflection
20. BLOOD SUPPLY UVEAL TRACT
• SHORT PROSTERIOR CILIARY ARTERIES
– BRANCHES OF OPTHALMIC ARTERY
– DIVIDES INTO 10-20 BRANCHES, PIERCE SCLERA
