Anatomy of Anterior chamber angle

1. ANATOMY OF ANTERIOR
CHAMBER ANGLE
MODERATOR : PRESENTER:
NIRAJ DEV JOSHI ASHI LAKHER
ARJUN NEUPANE

2. Presentation layout
Introduction
Angle structures and its
identification
Function
Biochemical and physio-chemical
properties
Clinical co-relation
Aqueous humour production and
drainage

3. Anterior Chamber
 A fluid filled space at the anterior most part
of eye.
 Bounded anteriorly by back of cornea and
posteriorly by anterior surface of iris and
part of ciliary body.
 Angle subtended is known as ”Anterior
chamber angle”.

4.  3mm deep in normal adult ,shallow in young
children and young people.
 It contains about 0.25ml of aqueous humour.

5. Posterior Chamber
 Triangular in shape.
 Contains about 0.06ml of aqueous humour.
 Bounded :
- anteriorly by posterior surface of iris and
part of ciliary body
-posteriorly by crystalline lens and its zonules
-laterally by ciliary body

6. Embryology
 Anterior chamber cavity is formed as a slit in the
mesenchyme between surface ectoderm and
developing iris.
 Mesenchyme anterior to slit→corneal endothelium
 Mesenchyme posterior to slit→primary pupillary
m/m
 Angle of anterior chamber (Iridocorneal Angle) :
 Loosely organised mesenchymal cell (neural
crest) occupies angle – trabecular meshwork .

7.  A continuous layer of endothelium forms a
closed cavity of anterior chamber.
 Anterior surface of iris insert infront of
primordial trabecular meshwork.
 In 3rd trimester endothelial layer progressively
disappear from pupillary m/m and iris cavitates
over the anterior chamber angle.
 Development of trabecular lamella and
intertrabecular space.
 End of 3rd month- schlemm’s canal derived
from mesodermal mesenchyme.

8. Posterior chamber
 Develops as a split in the mesenchyme
posterior to developing iris and anterior to
developing lens
 Anterior chamber and posterior chamber
communicate when pupillary membrane
disappears and pupil is formed.

9. Structures forming Angle
of anterior chamber
• Ciliary Band
• Scleral Spur
• Trabecular Meshwork
• Schwalbe’s Line

10. Ciliary Band
 Most posterior
landmark in angle
recess .
 Formed by anterior part
of ciliary body.
 Appears grey band in
gonioscopy

11. Scleral Spur
 Pale, translucent narrow strip of scleral
tissue.
 Structure beneath schlemm canal and
trabecular meshwork.
 Appears as prominent white line in
gonioscopy

12. Trabecular Meshwork
 Broad band of tissue
extending from Scleral
Spur to Schwalbe’s Line.
 No pigmentation at birth
but develops pigment with
increasing age (color
varies from faint tan to
dark brown)

13. Schwalbe’s Line
 Marks the anterior limit of the structures
forming angle of anterior chamber.
 Formed by the prominent end of the
descemets membrane of the cornea.

15. Physiochemical properties
Volume- about 0.31ml
• 0.25ml in anterior chamber
• 0.06ml in posterior chamber
Refractive index: 1.336
Density: Greater than that of water
Osmotic Pressure: Hyperosmotic to
plasma by 3 to 5 mOsm/l
 pH: pH of 7.2

16. Biochemical properties
Water: Constitutes of about 99.9% water
Proteins (Colloid Content): 5-16mg/100ml
Amino Acids
Non-colloidal Constituents:
• Na, K , Ca, Mg, Cl, HCO3 , Lactate,
Pyruvate, Ascorbate, Urea, Glucose
Inulin and Steroid
Prostaglandins
Cyclic AMP

17. Function
1. Maintainance of IOP - Aqueous humour
helps in maintaining the shape and internal
structure arrangement of eye.
2. Optical function – corneal aqueous
interface act as diverging lens of low power.
3. Clearing -the lens matter remnant and
product of inflammation from AC.

18. 4. Metabolic role : By providing substrate and
removing metabolite from avascular occular
surface as follows :
• takes glucose and oxygen
• release lactic acid and carbondioxide
Cornea
• takes oxygen,glucose,amino acids
potassium
• release lactate,pyruvate and sodium
Lens
• amino acid and glucose pass into the
vitreous from aqueous
Vitreous and
retinal
metabolism

19. Blood Occular Barrier
 Prevents the large molecular size substance
entering the cavities(anterior chamber
,posterior chamber).
1. Blood aqueous barrier : Created by
-tight junction between cells of inner non-
pigmented epithelium of ciliary process.
-non fenestrated endothelium of the iris
capillaries.

20. 2. Blood retinal barrier :
-tight junction of retinal capillaries,endothelial
cells.
-tight junctional complex located between
adjacent RPE.

22. Reason For Assessment
Of Anterior Chamber
 Rule out anterior segment inflammation.
 Differentially diagnose open angle , close angle ,
primary glaucoma and secondary glaucoma.
 Assess eye at risk from developing anterior
chamber sequelae to other disease. Eg:DM,CRVO

23. Methods For Assessment Of
Anterior chamber angle
 Iris shadow test
 Van herick method
 Gonioscopy

24. 1. Iris shadow test
 Patient fixates at object 6m away.
 Pentorch is projected temporally in same
horizontal plane of eye to be examined.
 Nasal aspect of iris to be observed.
 At this point determine what % of the nasal
iris is illuminated.

26. Based on the amount of iris
illuminated AC depth can be
graded

27. Grade
% of nasal
iris
illuminated
Angle type Closure possibility
1 25%
Extremely narrow
angle Very likely
2 50%
Moderately narrow
angle possible
3 75% Open angle Unlikely to impossible
4 100% wide open angle impossible

28. Indication :
 Infants
 Severly ill patient
 Bed-ridden
 Demented pt
 Un coperative pt

29. 2. Van herick method
 Common method to assess ACA
 using slit lamp biomicroscopy.
 Uses an optic section placed near the limbus
with light source at 30-45 degree.
 Biomicroscope is placed directly before pt
eye.
 Peripheral AC depth is compared to corneal
thickness.

31. Grade
Relation between corneal
thickness and anterior
chamber depth
Interpretation
0 closed closed
1 1 : <1/4 Extremely narrow angle
2 1 : ¼ Moderate narrow angle
3 1 : 1/2 Mild narrow angle
4 1 : 1 wide open

32. 3. Gonioscopy
 Enables clinical examination of the periphery
of Anterior chamber angle.
 Generally light rays coming from the angle
approach the cornea-air interface at an angle
more than critical angle and undergoes total
internal reflection.
 In gonioscopy , light ray which emanates from
from AC angle enters contact lens and are
made to pass through new contact lens-air
interface.

33. Types of gonioscopy
 Most commonly used gonio lens is the
goldmann three mirror lens.

34. Shaffer’s system of
grading the angle width

36. Abnormality in Anterior
chamber
1. Hyphema :
• Blood in anterior chamber.
• usually due to trauma ,iris neovascularization.
2.Hypopyon :
• pus in AC.
• Found in inflammatory condition.

37. 3. Cells:
• small particle floating in aqueous.
• usually WBCs,RBCs and pigmented
Cells.
4. Flare :
• Appears as hazy cloudy aqueous.
• Usually found in trauma, uveitis ,keratitis.

38. AQUEOUS PRODUCTION

39. ANATOMY OF CILIARY BODY
 Anterior portion of uveal tract located
between iris and choroid.
 Site of aqueous production
 Triangular in cross-section ; apex contiguous
with choroid & base close to iris
 Anterior portion of ciliary body is k/a Pars
Plicata/Corona Ciliaris , characterized by
Ciliary process consisting of 70 radial ridges
& equal no. of smaller ridges

40.  Pars plicata accounts for 25% of total length
of CB having surface area of 6 cm2 for
ultrafiltration & active fluid transport , being
actualsite of aqueous production
 Posterior portion is pars plana/orbicularis
ciliaris,relatively flat & pigmented inner
surface & is continuous with choroid at ora
serrata
 Ciliary body is composed of muscle , vessels
& epithelium

41. CILIARY MUSCLES
 3 muscles fibers
 Longitudinal muscle fiber: Contraction opens
Trabecular meshwork & Schlemn’s canal
 b)Circular Muscle fiber : Contraction relaxes
zonules , ↑ses lens axial diameter & its convexity
 Oblique Muscle fibers : Contraction widen the
uveal trabecular

42. PHYSIOLOGY OF AQUEOUS PRODUCTION
 The aqueous humour is primarily derived from
plasma within capillary network of ciliary
process.
 Three physiologic processes which
contribute to formation and chemical
composition of aqueous humour are:
1) Ultra-filtration
2) Active transport
3) Diffusion

43. ULTRAFILTRATION
 Process by which fluids and its solutes crosses
semipermeable membrane under pressure gradient
 As blood passes through the capillaries of the
ciliary processes, about 4% of the plasma filters
through the fenestrations in the capillary wall into
the interstitial spaces between the capillaries
and the ciliary epithelium
 Water and water soluble substances,limited by
size and charge, flow into stroma of ciliary
process from capillaries

44.  The high conc. of colloid in the tissue space
of ciliary processes favours the movement of
water from the plasma into the ciliary stroma
but retards the movements from ciliary
stroma into posterior chamber.
 latter requires active processes which occurs
in tandem with ultra-filtration

45. ACTIVE TRANSPORT
 Active transport (secretion) is an energy-
dependent process that selectively moves a
substance against its electrochemical gradient
across a cell membrane.
 majority of aqueous humor formation depends on
an ion or ions being actively secreted into the
intercellular clefts of the non-pigmented ciliary
epithe-lium beyond the tight junctions
 In the small spaces between the epithelial cells ,
the secreted ion /ions create sufficient osmotic
forces to attract water.

46.  Water soluble substances of larger size or
greater charge are actively transported
across NPE
 The best current evidence suggests that the
paired Na/H and Cl/HCO transports Na/Cl from
stroma into the cell.

47.  Main ions to be actively transported across
NPE include
 Sodium
 Chloride
 Bicarbonate
 Active transport of Na+ - key feature of
aqueous production
 role of aqua-porins in active transport of
water

48. DIFFUSION
 Movement of substance across a membrane along
its concentration gradient .
 As aqueous humour passes from PC to AC,
sufficient diffusional exchange with surrounding
tissues occur so that AC aqueous resembles
plasma more closely than posterior aqueous
humour.
 Aqueous humour provides glucose, amino acids,
oxygen, and potassium to surrounding tissues and
removes carbon dioxide, lactate, and pyruvate.

49. BLOOD AQUEOUS BARRIOR
 The blood–aqueous barrier consists of all of the
barriers to the movement of substances from the
plasma to the aqueous humor
 formed by tight junctions between cells of NPE of
ciliary body and tight junctions of iris capillary
endothelial cells
 In some situations (e.g., intraocular infection), a
breakdown of the blood–aqueous barrier is clearly
therapeutic because it brings mediators of cellular and
humoral immunity to the interior of the eye.
 In other situations (e.g., some forms of uveitis and
following trauma), the breakdown of the barrier is
inappropriate and favors the development of
complications, such as cataract and synechia
formation.

50.  This barrier is not absolute as medium sized
water soluble substances may penetrate it
but at much slower rate.
 Lipid solubility greatly facilitates ability of
substance to penetrate blood ocular barrier

51. STEPS OF AQUEOUS FORMATION
 Active secretion → 70%
 Ultrafiltration →20% and
 Osmosis → 10%

53. ACTIVE TRANSPORT OF STROMAL
FILTRATES
 The net effect of ion transport systems
located in PE and NPE are:
 Low level of sodium in both epithelial layers
 High level of potassium and ascorbate
 Control of intracellular pH

54. PASSIVE TRANSPORT ACROSS NON-
PIGMENTED CILIARY EPITHELIUM
 Active transport across non-pigmented ciliary
epithelium results in osmotic and electrical
gradient
 To maintain balance of osmotic and electric
forces, water, chloride and other small
plasma constituents move into posterior
chamber by Ultrafiltration and Diffusion

55. AQUEOUS HUMOUR COMPOSITION
 Substance Aqueous Plasma
(nmol/kg) humour
 Na+ 163 176
 Cl- 126 117
 HCO3- 22 26
 PH 7.21 7.40
 Ascorbate 0.92 0.06
 Protein 0.02% 7%

56. RATE OF AQUEOUSHUMOR FORMATION
AND MEASUREMENT TECHNIQUES
 Rate of aqueous humor formation of 2–3µl/min
 The techniques for measuring aqueous humor
formation can be divided into two major
categories:
 1) pressure-dependent methods
 2) tracer methods

58. Factors affecting aqueous humour
Formation
 Diurnal fluctuation : Aqueous flow is higher
in the morning than in the after-noon. The
rate of aqueous formation during sleep is
approximately one-half the rate upon first
awakening
 Age and sex : appears to be similar in males
and females. There is a reduction in aqueous
formation with age (particularly after age
60).Decline in aqueous production of about
3.2% per decade in adults

59.  Intraocular pressure: Aqueous humor
formation increases or decreases to changes
in IOP.
 Neural control : stimulation of the cervical
sympathetic chain decreases aqueous humor
production

60. Agents that affect aqueous humour
formation
Adrenergic agonist Decreases
Pilocarpine Slightly increases
Quabain Decreases
Carbonic anhydrase inhibitor Decreases

61. Intra Ocular Pressure
 Normal level of IOP maintained by a dynamic
equilibrium between aqueous humor formation,
aqueous humor outflow and episcleral venous
pressure.
 Normal range of IOP: 15.5 ±2.57 mm of Hg
 IOP = Intraocular pressure,
 AHF = Aqueous humor formation,
 Fu = Uveoscleral outflow,
 Ctrab = Facility of outflow from the anterior
chamber via the TM and Schlemm’s canal,
 Pe = Episcleral Venous Pressure
IOP = [(AHF - Fu ) /Ctrab ] + Pe

62. Acute increase in IOP Chronic increase in IOP Decreased
IOP
Acute angle closure
glaucoma
Primary open angle
glaucoma
Ruptured globe
Inflammatory open-angle
glaucoma
Phthisis bulbi
Suprachoroidal
hemorrhage
Retinal/choroidal
detachment
Hyphema Iridocyclitis
Retrobulbar hemorrhage Severe dehydration
Ocular ischemia

63. Aqueous Drainage System
4/12/2021

64. Aqueous Drainage System includes:
Trabecular Meshwork
Schlemm’s Canal
Collector Channels
Episcleral Veins

65. Anatomy of Outflow System:
I.Trabecular Meshwork
Sieve like structure through which
aqueous humor leaves the eye
Bridges the scleral sulcus and converts it
into a tube which accommodates the
Schlemm’s Canal
Allows the bulk flow aqueous out of the
anterior chamber but prevents blood
reflux into anterior chamber.
 Hence, forms the crucial part of normal
blood-aqueous barrier

66. Trabecular Meshwork consists of
three portions namely:
Uveal Meshwork
Corneo-scleral
Meshwork
Juxta-canalicular
Meshwork

68. Trabecular Meshwork (Contd.)
1) Uveal Meshwork
 Innermost part of trabecular meshwork,
extends from iris root and ciliary body to
Schwalbe’s line
 2 to 3 layers thick
 Opening size 25µ to 75µ
 On electron microscopy each trabeculae is
seen to have concentric layers:
Central collagenous core
Middle basement membrane
Outer trabecular cells

69. Trabecular Meshwork (Contd.)
2) Corneo-scleral Meshwork
 Larger middle portion extending from
scleral spur to lateral wall of scleral
sulcus
 Consists of flat sheets of trabeculae
with elliptical openings ranging from 5µ
to 50µ
 Openings are progressively smaller as
they approaches schlemm’s canal.

70. Trabecular Meshwork
(Contd.)
3) Juxta-canalicular Meshwork
 Outermost portion of trabecular meshwork
 It mainly offers resistance to normal
aqueous outflow
 This narrow part of trabeculum connects
corneo-scleral meshwork with Schlemm’s
Canal.

71. II. Schlemm’s Canal
 Endothelial lined oval channel present
circumferentially in the scleral sulcus
 The endothelial cells of inner wall are
irregular, spindle shaped and contains
giant vacuoles
 The endothelial cell of outer wall are
smooth and flat containing numerous
opening of collector channels.

72.  Canal is located directly anterior to
scleral spur and is normally not seen.
 Blood in canal is more common under
conditions of elevated episcleral venous
pressure,uveitis or scleritis
 Hypotony may also cause blood to reflux
into the canal.

73. c) Collector Channels
 Also k/a Intrascleral Aqueous Vessels
 25 to 35 in number
 Leave Schlemm’s Canal at oblique angles
to terminate ultimately into episcleral
veins

74. Consists of two systems
namely:
 Direct System
 drained by about 8 larger vessels
 drain directly into episcleral veins
 Also known as Aqueous Veins or
Laminated Veins of Goldmann
 Indirect System
 Constituted by fine interconnecting
channels before eventually entering
into episcleral veins

76. Physiology of Drainage of
Aqueous Humor
 Aqueous Humour is clear relatively cell
free, protein free fluid, formed by the ciliary
body epithelium in posterior chamber
 Passes between iris and lens to enter
anterior chamber through pupil

77. Thermal Currents in
Anterior Chamber
 In anterior chamber, aqueous is subjected to
thermal currents because of temperature
difference between vascular and warmer iris
and avascular and cooler cornea
 Cornea is cooler compared to iris because of
the cooling effect of tear,due to its
evaporation

78. Exits the eye at anterior
chamber angle via two
pathways:
 Conventional Trabecular Pathway
 Unconventional Uveo-scleral
Pathway

79. I. Conventional Trabecular Pathway
 About 75 to 90% of aqueous is drained via
this route into episcleral veins
 Circulatory path for aqueous humor return to
the vascular system
 Free Flow from trabecular meshwork upto
Juxtacanalicular meshwork, along with inner
wall of Schlemm’s Canal, offer some
resistance to the flow and hence helps in
maintaining relatively stable IOP

80. II. Unconventional Uveoscleral
Pathway
 Approximately 10 to 25% of total aqueous
drained via this pathway
 The main resistance to uveoscleral flow is by
tone of the ciliary muscle
 Factors like Pilocarpine that contracts ciliary
muscle lower the uveoscleral outflow
 Whereas, the factors such as atropine that
relax ciliary muscle raise the uveoscleral
flow

81.  Aqueous Humor enters ciliary muscle
through uveal trabecular meshwork,
ciliary body face and iris root
 Passes posteriorly between bundles of
ciliary muscle until it reaches supra
ciliary and suprachoroidal spaces
 Leaves eye through spaces around
penetrating nerves and blood vessels
through sclera
Venous
Circulati
on
Supra-
choroida
l Space
Across
Ciliary
Body

82.  Uveoscleral drainage is possible only
beacause of pressure gradient of 2-4
mm of hg between suprachoraoidal
space and aqueous chamber
 This pressure difference may be
reversed with age or trabeculectomy
causing choroidal effusion.
Clinical Correlation
Prostaglandins used to reduce IOP in various conditions
including glaucoma reduce IOP by increasing the aqueous
drainage via this pathway.

83. Ciliary processes
Aq in posterior chamber
Aq in anterior chamber
Trabecular Meshwork
Schlemn’s canal
Collector channels
Episcleral veins
Ciliary body
Suprachoroidal space
Venous circulation of ciliary body,
choroid and sclera

85. Trabecular Meshwork and Schlemm’s
Canal Endothelial Cells
 Specialized characters:
Active phagocytic properties
High levels of cytoskeletal actin
Lower levels of microtubules
 Presence of desmin and vimentin shows
similarity to smooth muscle cells

86. Classification of glaucoma
1) Congenital/ developmental glaucoma
2) Primary adult glaucoma
Primary open angle glaucoma(POAG)
Primary angle closure glaucoma(PACG)
3) Secondary glaucoma

87. PRIMARY ANGLE CLOSURE
GLAUCOMA
 Defining criterias:
 Irido-trabecular contact noted in gonioscopy(>270)
 PAS is formed
 IOP is elevated (> 24 mmHg)
 Optic disc shows glaucomatous changes as POAG
 Visual fields shows typical glaucomatous changes.
 Pathogenesis:
 Pupillary block mechanism
 Plateau iris configuration and syndrome
Pushing of peripheral iris forward by ciliary process.
 Phacomorphic mechanism
Abnormal lens position

88. Pigment dispersion syndrome/
Pigmentary glaucoma
 Pigment dispersion refers to a pathologic
increase in the TM pigment, associated with
characteristic mid-peripheral, radial iris TIDs.
 The pigment may ultimately obstruct the TM,
leading to increased IOP and secondary open-
angle glaucoma.
 Pigment release is caused by mechanical rubbing
of post surface of iris with zonular fibrils
Clinical features
 Mid-peripheral, spokelike iris TIDs
 Deposition of pigments in ant segments as iris,
posterior surface of cornea

89.  Deposition of pigments in ant segments as iris, posterior
surface of cornea
 Dense homogeneous pigmentation of the TM for 360
degrees (seen on gonioscopy) in the absence of signs of
trauma or inflammation.

90. Neovascular glaucoma
 Formation of neovascular m/m involving the angle of AC
 a/w neovascularization of iris (rubeosis iridis)
 PDR
 CRVO
 Sickle cell retinopathy

91. THANK YOU
• Reference