The document summarizes the anatomy and physiology of aqueous humour formation, circulation, and drainage. It discusses how aqueous humour is formed primarily through active transport in the ciliary body, circulates from the posterior to anterior chamber, and drains out through the trabecular meshwork and Schlemm's canal into episcleral veins. The key structures involved are the ciliary body, anterior chamber angle, trabecular meshwork, and Schlemm's canal. Aqueous humour production and outflow are regulated by various factors and drugs.

1. AQUEOUS HUMOUR
FORMATION,
CIRCULATION AND
DRAINAGE
DR. IFRAD TASNIM
RESIDENT ( PHASE-A)
DEPARTMENT OF OPHTHALMOLOGY

2. WHAT IS AQUEOUS HUMOUR ?
Is a clear, colourless, watery solution
Flows from posterior to anterior chamber
In healthy eye flow against resistance generates 15 mm hg

3. PHYSIOCHEMICAL PROPERTIES
• Volume of aqueous humour is about 0.31 ml.
• Refractive index of aqueous humour is 1.33332.
• It is slightly acidic with a ph in the anterior chamber of 7.2
• Normal aqueous production rate is 2.0-2.5µl/ min.
• Aqueous is slightly Hyperosmotic to plasma by 3-5
mOsml/L.

4. BIOCHEMICAL COMPOSITION OF
AQUEOUS HUMOUR
• Water: 99.9%
• Proteins: 5-16mg/100ml
• Amino acids: aqueous/plasma concentration varies from 0.08-3.14
• Non colloidal constituents: conc. Of ascorbate, pyruvate, lactate in
higher amount while urea and glucose are much less.
• Inulin and steroid
• Prostaglandins
• Cyclic AMP

5. ANATOMY OF AQUEOUS HUMOUR
FORMATION AND DRAINAGE
STRUCTURES
Primary ocular structures involved are
1. Cilliary body
2. Posterior chamber
3. Anterior chamber
4. Angle of anterior chamber
5. Aqueous outflow system

7. CILIARY BODY
Seat of aqueous production
Triangular in shape
Outer side- line with sclera with a supra choroidal space in betweeen
Inner side of ciliary body has two parts-
a) Anteriorly pars plicata(finger like projections-ciliary process)
b) Posteriorly pars plana
Ciliary muscle- non striated muscle -3 parts
1. Longitudinal or meridional fibers- helps in aqueous outflow
2. Circular muscles- helps in accomodation
3. Radial or oblique fibers- helps in aqueous out flow

10. ANGLE OF ANTERIOR CHAMBER
Formed by iris root, anterior part of ciliary body, scleral
spur, canal of schlemm, trabecular meshwork and
schwalbe’s line.
Anteriorly- schwalbe’s line
Posteriorly-iris
Major drainage pathway for aqueous humour.
Also known as filtration angle or iridocorneal angle.
Angle is wider in myopic eyes and narrow in
hypermetropes.

12. AQUEOUS HUMOUR FORMATION
Aqueous humour is formed from plasma by non-pigmentary
ciliary epithelium of the ciliary process of ciliary body (pars
plicata).
AQUEOUS HUMOUR IS FORMED IN
THE THREE STEPS-
• Ultrafiltration-20%
• Active secretion-70%
• Diffusion-10%

13. ULTRAFILTRATION
Also known as relative dialysis.
The process by which the fluid and solutes
cross through the semipermiable membrane.
Capillary blood flow-150 ml/min
4% through fenestrations
Favoured by hydrostatic pressure difference
between capillary and interstitial pressure.
Enough to move fluid to stroma but further
requiered active transport.
Leads to form stromal pool

14. FORMATION OF STROMAL POOL

15. ACTIVE TRANSPORT
Is done by non-pigmented ciliary epithelium(NPCE) (about
80% - 90% of total aqueous formation)
Energy dependent process
Selectively moves substances against its electrochemical
gradient across the basolateral membrane of NPCE.
2 enzyme play key role-
Na+-K+ ATPase
Carbonic anhydrase

16. ACTIVE TRANSPORT
As a result of the primary active transport of Na+, other
ions (eg: Clˉ ) and molecules ( eg: ascorbic, some amino
acids) are transported over the epithelium by secondary
active transport. There is also a passive transport for HCo3ˉ.
To maintain electroneutrality, anions must accompany the
actively secreted Na+, Clˉ can pass through Clˉ channel in
basolateral membrane. HCo3ˉ can enter aqueous humour via
exchange with Clˉ.

17. ACTIVE TRANSPORT
The active ransport of Na+ and the accompanying anions
create high osmolarity on the basolateral side of NIE cell,
which causes diffusion of water out of the cells. The
movement of water is facilitated by aquaporin(1 & 4).
Na+ and Clˉ must continuously enter the pigmented
epithelial cell for the ontinuous secretion of aqueous
humour. This is achieved by Na+/H+ and Clˉ/HCo3ˉ antiport
and by the Na+-K+-2Clˉ co-transporter.

18. ACTIVE TRANSPORT
The another enzyme carbonic anhydrase is abundantly
present in the basolateral membrane of PE & NPE. It
converts water and Co2 to carbonic acid and subsequently
dissociate into H+ & HCo3ˉ. This HCo3ˉ is essential for
active secretion of aqueous humour.

19. ACTIVE SECRETION

20. DIFFUSION
• Due to active transport of the substance from the stromal filtrate
into posterior chamber, there occur osmotic and electrical
gradient
• Therefore water, chloride and other small plasma constituents
move into the P/C to equalize the osmotic and electrical gradient
by the process of diffusion.

21. MATHEMATICAL EQUATION OF A.H
FORMATION
MODIFIED GOLDMANN EQUATION
 Pe- episcleral venous
pressure
 Fin –aqueous flow
 Fu- uveoscleral flow
 Ctrab- trabecular
meshwork flow

22. FACTORS AFFECTING AQ HUMOR
FORMATION
• Avg is 2.0-2.5 micro lit/min
• Diurnal variation : maximum in morning hours & min late at night,
due to decreased stimulation of ciliary epithelium by catecholamines
during sleep.
• Age and sex: similar in males & females , reduces with age.
• Ocular inflammation ,hypothermia ,systemic acidosis & anesthetics
like halothane , barbiturates & ketamine decrease formation.

23. FACTORS AFFECTING AQ HUMOR
FORMATION
• Blood flow to ciliary body: profound vasoconstriction
decreases formation.
• Sympathetic system: stimulation by β2 & inhibition via α2
receptors.
• Parasympathetic system: decreases via M3 receptors.
• Intracelluar regulators: cyclic AMP increases aqueous
formation.

24. AQUEOUS HUMOUR OUTFLOW
Ciliary processes
Trabecular meshwork
Schlemm’s canal
Collector channels
Episcleral veins
Trabecular
(conventional)
outflow-90%
Ciliary body
Suprachoroidal space
Venous circulation of
ciliary body, sclera and
choroid
Uveoscleral
(unconventional)
outflow -10%
iris
Aqeous in the posterior
chamber (through pupil)
Anterior chamber

25. C A
B
Routes of aqueous outflow: A, trabecular; B,
uveoscleral; C, iris

27. CELLULAR ORGANIZATION OF THE
TRABECULAR OUTFLOW PATHWAY
 The trabecular meshwork: (trabeculam) is a sieve like
structure at the angel of the anterior chamber (AC) through
which 90% of aqueous humour leaves the eye. It has three
component
The uveal meshwork is the innermost portion, consisting of
cord-like endothelial cell-covered strands arising from the iris
and ciliary body stroma. The intertrabecular space are
relatively large and offer little resistance to the passage of
aqueous.

28. CELLULAR ORGANIZATION OF THE
TRABECULAR OUTFLOW PATHWAY
The corneoscleral meshwork lies external to the uveal meshwork
to form the thickest portion of the trabeculum. It is composed of
layers of connective tissue stands with overlying endothelial-like
cells. it confers greater resistance to flow than uveal meshwork.
The juxtacanalicular (cribiform) meshwork is the outer part of the
trabeculam, and links the corneoscleral meshwork with the
endothelium of the inner wall of the canal of sclemm. It consists
of cells embedded in a dense extracellular matrix with narrow
intracellular spaces, and offers the majors portion of normal
resistance to aqueous outflow.

29. CELLULAR ORGANIZATION OF THE
TRABECULAR OUTFLOW PATHWAY
The schlemm canal is a circumferential channel within the
perilimbal sclera.
The inner wall is lined by irregular spindle-shaped
endothelial cells containing infoldings (gaint vacuoles) that
are thought to convey aqueous via the formation of
trabecular pores.
The outer wall is lined by smooth flat cells and contains the
opening of collector channels.

30. CELLULAR ORGANIZATION OF THE
TRABECULAR OUTFLOW PATHWAY
• COLLECTOR CHANNELS
25-30 intrascleral aqueous vessels
Valveless,wide at origin
Direct system
Indirect system
• EPISCLERAL VEINS
Drain ultimately in to cavernous sinus via ant ciliary and sup ophthalmic
veins

32. VACUOLATION THEORY OF AQUEOUS
TRANSPORT ACROSS SCHLEMM’S CANAL
• Vacuolation theory of aqueous transport
across the inner wall of the schlemm's
canal:
1. Non-vacuolated stage.
2. Stage of early infolding of basal surface
of the endothelial cell.
3. Stage of macrovacuolar structure
formation.
4. Stage of vacuolar transcellular channel
formation.
5. Stage of occlusion of the basal
infolding

33. PHARMACOLOGICAL REGULATION OF
AQUEOUS HUMOUR OUTFLOW
Increase production
Beta adrenergic agents – epinephrine, salbutamol, isoprenaline, terbutaline
Hydrocortisone adminestration systemically
Intracameral epinephrine
Decreased production
CA inhibitors - acetazolamide
Beta blockers - timolol, betaxolol
Ouabain
Alfa-2 agonist – apraclonidine, brimonidine