Aqueous Humour dynamics

1. AQUEOUS HUMOR DYNAMICS
BY DR. RAHUL
MODERATOR:DR. DHAMANKAR

2. ANATOMY
UVEAL TRACT CONSIST OF
IRIS
CILIARY BODY
CHOROID

3. IRIS
CILIARY ZONE
PUPILLARY ZONE
MICROSCOPIC
ANTERIOR LIMITING LAYER
STROMA
ANTERIOR PIGMENTED EPITHELIAL LAYER
POSTERIOR PIGMENTED EPITHELIAL LAYER

4. CILIARY BODY
FORWARD CONTINUATION OF CHOROID
ANTERIOR PART HAVING FINGER LIKE
CILIARY PROCESSES CALLED PARS PLICATA
POSTERIOR SMOOTH PART PARS PLANA

5. CILIARY PROCESSES
THESE ARE FINGER LIKE PROJECTIONS
70-80 IN NUMBER
2 MM LONG AND 0.5 MM IN D
WHITE IN COLOUR
EACH PROCESS LINED BY 2 LAYERS OF EPITHELIAL CELLS
IT CONTAINS BLOOD VESSELS AND LOOSE CONNECTIVE
TISSUSE
SITE OF AQUEOUS PRODUCTION

6. ANATOMY

7. Ciliary epithelium
Nonpigmented - inner layer, adjacent to aqueous in
the posterior chamber,
consisting of columnar cells (cuboidal in pars plana).
Intercellular tight junctions (zonulae occludens) form
major element of blood-aqueous barrier.
Tips or crests of nonpigmented ciliary epithelia are
site of active secretion,
hence numerous mitochondria, rough
endoplasmic reticulum, pinocytic

8. Angle of anterior chamber
Clinically angle structures can be visualized by
goniosciopic examination
Starting from posterior to anterior
1)Ciliary band
2)Scleral spur
3)Trabecular meshwork
4)Schwalbes line

9. . Shaffer’s system of grading the angle width
Grade Angle width Configuration Chances of closure Structures
visible on gonioscopy
IV 35-45o Wide open Nil SL, TM, SS, CBB
III 20-35o Open angle Nil SL, TM, SS
II 20o Moderately narrow Possible SL, TM
I 10o Very narrow High SL only
0 0o Closed Closed None of the angle structures visible
SL = Schwalbe’s line, TM = Trabecular meshwork, SS = Scleral spur,
CBB = Ciliary body band

10. Shaffer’s system of grading
the angle width

11. Shaffer’s system of grading
the angle width

14. AQUEOUS OUTFLOW SYSTEM
IT INCLUDES
TRABECULAR MESHWORK
SCHLEMMS CANAL
COLLECTOR CHANNLES
AQUEOUS VEINS
EPISCLERAL VEINS

19. TRABECULAR MESHWORK
IT IS SIEVE LIKE STRUCTURE THROUGH WHICH AQUEOUS
HUMOUR LEAVES EYE
CONSIST OF 3 PORTIONS
1)UVEAL MESHWORK
-Innermost part of TM, extends from iris root and ciliary body to
schwalbes line
-the arrangement of uveal trabecular bands create opening of 25 mu to
75 mu
-least resistance to flow

20. 2)CORNEOSCLERAL MESHWORK
-larger middle portion ,extends from scleral spur to
lateral wall of scleral sulcus
-opening 5 mu to 50 mu
Moderate resistance to flow

21. 3)JUXTACANLICULAR , ENDOTHELIAL
MESHWORK
It form outer most part
Lined on either side by endothelium
IT MAINLY OFFERS NORMAL RESISTANCE TO
AQUEOUS OUTFLOW

23. AQUEOUS DRAINAGE

24. SCHLEMMS CANAL
IT IS ENDOTHELIAL LINED OVAL CHANNEL PRESENT
CIRCUMFERENTIALLY IN SCLERAL SULCUS
THE ENDOTHELIAL CELLS OF ITS INNER WALL ARE
IRREGULAR, SPINDLE SHAPED AND CONTAIN GAINT
VACUOLES
THE OUTER WALL OF THE CANAL IS LINED BY
SMOOTH FLAT CELLS
CONTAINS OPENING OF COLLECTOR CHANNELS

25. COLLECTOR CHANNELS
ALSO CALLED INTRASCLERAL AQUEOUS VESSELS
ABOUT 25-35 IN NUMBER
LEAVES SCHLEMMS CANAL AT OBLIQUE ANGLES TO
TERMINATE INTO EPISCLERAL VEINS
NO VALVES ARE PRESENT IN COLLECTOR CHANNELS
THESE INTRASCLERAL AQUEOUS VESSELS CAN BE
DIVIDED INTO TWO SYSTEM

27. DIRECT SYSTEM
ON SLIT LAMP , THESE APPEAR AS CLEAR VESSELS WITH
AQUEOUS CALLED AS AQUEOUS VEINS BY ASCHER
AS THESE VESSELS TERMINATE INTO EPISCLERAL AND
CONJUNCTIVAL VEINS IN LAMINATED JUNCTIONS ,CALLED AS
LAMINATED VEIN OF GOLDMANN

28. EPISCLERAL VEINS
 MOST OF AQUEOUS VESSELS DRAIN INTO EPISCLERAL VEINS

29. Aqueous humor
 is a relatively cell free,protein free
 fluid formed by non pigmented ciliary epithelium
Slightly hypertonic
Acidic , PH IS 7.2
Marked excess of ascorbate
Marked deficit of proteins
Slight excess of chloride and lactic acid

30. PHYSICOCHEMICAL PROPERTIES
VOLUME
0.31 ML (0.25 ml in AC 0.06 ml in PC)
REFRACTIVE INDEX
1.336 SLIGHTLY LOWER THAN CORNEA
SLIGHT DIVERGENCE OF LIGHT AS IT PASS CORNEA -AQUEOUS
INTERFACE
DENSITY
SLIGHTLY GREATER THAN WATER

31. OSMOTICS PRESSURE
AQUEOUS IS SLIGHTLY HYPEROSMOTIC TO PLASMA BY 3 TO 5
MOSM/L
PH
ACDIC IN AC 7.2
RATE OF FORMATION
2.3 Ul/min

32. Formation of aqueous humour
Ciliary processes are site of aqueous production
The various constituents of aqueous humour have to
pass 3 tissue layers of cililary processes
1)capillary wall
2)stroma
3)two layers of epithelium

33. Formation processes involved
1)diffusion 10 %
2)Ultarafiltration 20%
3)secretion 70%

34. DIFFUSION
Diffusion - lipid-soluble substances are transported
through the lipid portions of the cell membrane
proportional to a concentration gradient across the membrane

35. ULTRAFILTRATION
Ultrafiltration - water and water-soluble substances,
limited by size and charge, flow through theoretical
micropores in the cell membrane in response to an
osmotic gradient or hydrostatic pressure; influenced
by
intraocular pressure,
blood pressure in the ciliary capillaries,
and plasma oncotic pressure

36. Diffusion and ultrafiltration are both passive
mechanisms, with lipid- and water-soluble substances
from the capillary core traversing the stroma and
passing between pigmented epithelial cells and
limited by the tight junctions of the non-pigmented
epithelial cells
c. Active transport (secretion) - water-soluble
substances

37. SECRETION
Active transport (secretion) - water-soluble substances
of larger size or greater charge are actively
transported across the cell membrane, requiring the
expenditure of energy; Na-K ATPase and glycolytic
enzymes are present in nonpigmented epithelial cells.
Active transport is decreased by hypoxia, hypothermia,
and any inhibitor of active metabolism.
 Active transport accounts for the majority of aqueous
production.
MEDIATED BY GLOBULAR PROTEINS IN MEMBRANE

38. STEPS OF AQUEOUS FORMATION

39. FORMATION OF STROMAL POOL

40. PASSIVE TRANSPORT ACROSS NON PIGMENTED
CILIARY EPITHELIUM
Active transport across non pigmented epithelium
result in osmotic and electical gradient
Sodium is primarily responsible for movement of
water into posterior chamber and its secretion is
major factor in formation of aqueous

41. ACTIVE TRANSPORT OF STROMAL FILTRATES
The tight junction between non pigmented epithelial
cells creat part of blood aqueous barrier
Substances actively transported are
1)NA
2)chloride
3)potassium
3)ascorbic acid
4)amino acid n bicarbonate

42. Control of aqueous formation
ADRENERGIC INNERVATION
CILIARY EPITHELIUM DOES NOT SHOW NERVE SUPPLY , BUT
VESSELS HAVE NERVE SUPPLY
MAJORITY OF RECEPTORS IN CILIARY BODY ARE α2 & β2
RECEPTORS
STIMULATION OF α 2 RECEPTOR LOWER AQUEOUS HUMOUR
PRODUCTION THROUGH INHIBITION OF ADENYLATE CYCLASE
STIMULATION OF β 2 RECEPTOR LEADS TO INCREASE IN
PRODUCTION BY STIMULATION OF ADENYLATE CYCLASE

43. α 2 AGONIST LIKE CLONIDINE AND β2
ANTAGONIST LIKE TIMOLOL DECREASES
AQUEOUS PRODUCTION

44. Functions
It serves the circulatory function for the avascular
tissues of the eye.
Brings essential nutrients such as oxygen glucose and
amino acids .
Removes harmful substances such as lactic acid and
CO2

45. Maintains the IOP and structural integrity of the eye.
Contains high concentrate of ascorbate which act to
scavenge free radicles and protects against effects of
radiation.
Facilitates cellular and humoral immunity in case
inflamation and infections

46. Conditions decreasing SECRETION
1.General conditions
 Age
Diurnal
Exercise

47. 2. Systemic conditions
Decrease BP
Reduction in internal carotid arterial blood flow
Diencephalic stimulation
Acidosis
General anaesthesia

48. 3.Local conditions
Increased IOP
Uveitis
Retinal detachment
Retrobulbar anaesthesia
Choroidal detachment

49. 4.Pharmacological agents
1)BETA BLOCKERS
DECREASE IN AQUEOUS PRODUCTION BY BETA 2 RECEPTOR
STIMULATION IN CILIARY PROCESSES
TIMOLOL ,
BETAXOLOL ,
LEVOBUNOLOL
CARTEOLOL

50. 2)PILOCARPINE
PILOCARPINE CONTRACTS LONGITUDINAL MUSCLE OF CILIARY
BODY AND OPENS SPACE IN T.M , SO MECHANICALLY
INCREASEING AQUEOUS OUTFLOW
3)CARBONIC ANHYDRASE INHIBITOR
BY DECREASING AQUEOUS SECRETION
DORZOLAMIDE
4) PROSTAGLANDINS
ACT BY INCREASING UVEO SCLERAL OUTFLOW OF AQUEOUS

51. ADRENERGIC DRUGS
-SELECTIVE ALPHA 2 ADRENERGIC AGONIST BY DECREASING
AQUEOUS PRODUCTION
-APRACLONIDINE
-BRIMONIDINE

52. CONDITIONS DECREASING SECRETION
5.Surgical conditions
Cyclodialysis
Cyclocryothermy
Cyclodiathermy
Cyclophoto coaguation.

54. THANK YOU