Anatomy and Physiology of Aqueous Humor Sumit Singh Maharjan 2. Anatomy 3. Angle of anterior chamber 4. Angle of the Anterior chamber 5. Gonioscopic grading of Angle 6. Aqueous Outflow system 7. Trabecular meshwork 8. Functions of Aqueous Humor • Maintenance of Intraocular pressure • Metabolic role  cornea  lens  vitreous and retina • Optical function • Clearing function 9. Physicochemical properties • volume: 0.31ml (0.25ml in Ant. Chamber and 0.06 in post chamber) • Refractive index: 1.336 • Density: slightly greater than water, its viscocity is 1.025-1.040 • Osmotic pressure: slightly hyperosmotic to plasma by 3-5mosm/l • PH: 7.2 • Rate of formation: 2-2.5microliter/min 10. Biochemical composition • 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 am

1. Anatomy and Physiology
of
Aqueous Humor
Sumit Singh Maharjan

2. Anatomy

4. Angle of anterior chamber

5. Angle of the Anterior chamber

6. Gonioscopic grading of Angle

7. Aqueous Outflow system

8. Trabecular meshwork

9. Functions of Aqueous Humor
• Maintenance of Intraocular pressure
• Metabolic role
 cornea
 lens
 vitreous and retina
• Optical function
• Clearing function

10. Physicochemical properties
• volume: 0.31ml (0.25ml in Ant. Chamber and 0.06 in
post chamber)
• Refractive index: 1.336
• Density: slightly greater than water, its viscocity is
1.025-1.040
• Osmotic pressure: slightly hyperosmotic to plasma by
3-5mosm/l
• PH: 7.2
• Rate of formation: 2-2.5microliter/min

11. Biochemical composition
• 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

12. Composition of Aq. humor of the ant.
and post. chamber
• Differs because of the constant metabolic
interchange during intraocular course
• Diffusional exchange across the iris is a significant
factor, since iris vessels are permeable to anions and
non-electrolytes
• Some striking differences are:
 Bicarbonate in post. chamber is higher because
freshly secreted fluid has a much higher
concentration and due to diffusion into the vitreous
and into the blood from iris and decomposition by
the acids formed by the lens and cornea metabolism,
its level decreases in ant aqueous

13.  Chloride concentration in newly formed aqueous is
lower because diffusion of chloride from the blood
raises the choride level in ant chamber
 Ascorbate concentration in post is higher because
diffusion occurs of ascorbic from the ant chamber to
blood

14. Factors affecting composition of the
Aqueous Humor
1. Blood-ocular barrier
• posterior blood-retinal barrier
• Anterior blood-aqueous barrier
2. Hemodynamic factors influencing stromal pool
3. Diffusional exchange across the iris
4. Metabolic process
5. Rate of aqueous drainage
6. The quality of aqueous

15. Blood-retinal barrier

16. Blood-aqueous barrier

17. Clinical application of blood ocular
barrier
• Hyperosmotic agents
• Ocular penetration of systemically administered
antibiotics

19. Formation of aqueous humor
• Ciliary processes are the site of aqueous production
• Aqueous humor primarily derived from plasma
within the capillary network of ciliary processes
• Presently it is agreed that diffusion, ultrafiltration,
and secretion play role in aqueous production at
different levels
• Major factor in aqueous production is active
secretion (70%), ultrafiltration accounts for 20% and
osmosis 10%.

20. Diffusion
In the process of aqueous production, the lipid soluble substance
are transported by diffusion through the lipid portions of the cell
membrane of the ciliary processes, proportional to a
concentration gradient across the membrane.

21. Ultrafiltration

22. Secretion
• Secretion implies an active process that selectively
transports some substances across the cell
membrane.
• Since energy is consumed, substance can be moved
across a concentration gradient.
• This mechanism is believed to be mediated by
globular proteins in the membrane and requires
energy.

23. Steps of Aqueous formation
1. Formation of stromal pool
2. Active transport of stromal filtrates
3. Passive transport across non-pigmented ciliary
epithelium

24. Formation of stromal pool

25. Active transport of stromal filtrates
• Tight junction between the non-pigmented epithelial
cells create part of blood-aqueous barrier
• Evidence of active transport occurs due to:
i. Abundant Na/K ATPase
ii. Presence of more mitochondria
iii. Higher adenyl cyclase activity
iv. Higher specific activity of glycolytic enzymes
v. Preferential incorporation of labelled sulphate and
macromolecules (primarily glycolipids and
glycoproteins).

26. Following substance from the stromal filtrates are actively
transported across epithelial cells
• sodium: approx 70% actively transported by a specific
secretory pump. Remaining 30% by diffusion or
ultrafiltration. Active transport is ATPase dependent .
Carbonic anhydrase acts to maintain the proper PH for
the Na/K ATPase system.
• Chloride: major % by diffusion and small % by active
transport and this appears to be dependent upon the
presence of Na and PH
• Potassium: by secretion and diffusion
• Ascorbic acid: secreted against large conc. gradient
• Amino acids: secreted by 3 carriers, one each for acidic,
basic and neutral molecules
• Bicarbonates: formation is catalyzed by carbonic
anhydrase. It influences fliud transport through its effect
on sodium.

27. Passive transport across non-
pigmented ciliary epithelium
• Active transport of the substance across the non-
pigmented epithelium results in an osmotic and
electrical gradient.
• To maintain the balance of osmotic and electrical
forces, water, chloride and other small plasma
constituent then move into the post chamber by
ultrafiltration and diffusion
• Sodium is primarily responsible for movement of
water into the posterior chamber and its secretion is
a major factor in the formation of aqueous

28. Evidence about the secretion of sodium is the key
factor in aqueous formation are:
• Presence of large conc. of Na/K ATPase especially at
the lateral interdigitations of the non-pigmented
layer
• Oubain which is an inhibitor of Na/K ATPase
effectively reduces aqueous formation
• Shrinkage of ciliary processes is inhibited by oubain
• Sodium accumulates in the post chamber after
parenteral administration of radioactive Na.

29. Rate of Aqueous Humor production
• 2-2.5microlitres/min
Methods of
measurement
Class 1
method
Fluorescein
technique
Radioactive
labelled
isotope
IV PAH or
fluorescein
Class 2
method
Perfusion of
eyes
Tonography Perilimbal
suction cup
method

30. Control of Aqueous formation
1. Adrenergic innervation
2. Role of vasopressin
3. Role of adenylcyclase
 CAMP activates specific protein kinase and thereby
results in specific protein phosphorylation
 protein kinase activity induced by CAMP may cause a
change in permeability of non-pigmented epithelium
4. Ultrafiltration and diffusion

31. Aqueous Humor drainage mechanism
• Uveoscleral (unconventional) outflow-pressure
independent
• Trabecular (conventional) outflow

32. Uveoscleral outflow

33. Trabecular outflow

34. Various mechanism of Aqueous
transport across schlemm’s canal
• Vacuolation theory
• Leaky endothelial cells
• Sonderman’s channels
• Contractile microfilaments
• Pores in endothelial cells

35. Vacuolation theory

36. Alteration of Aqueous in
disease(secondary aqueous)
Intraocular malignancy
• Plasma : aqueous ratio of LDH >1.50 in retinoblastoma
• <0.60 in rubeosis iridis, ROP and malignant melanoma
Uveitis
• IgG increase , IgM & IgA becomes detectable
• Ab against toxoplasma gondii & toxocara canis
Retinal disease:
• Photoreceptor cells in Aqueous and TB ---glaucoma associated with
rhegmatogenous RD
Glaucoma:
• Heavy molecular weight soluble protein--- phacolytic glaucoma

37. FACTORS CAUSING DECREASE AQUEOUS
• Hypothermia
• Acidosis
• Injection of hyperosmotic solution
• Drugs: halothane, barbiturates, ketamine, vasopressin
• Retinal detachment
• Ocular inflammation
FACTORS CAUSING INCREASE IN AQUEOUS
• Hyperthermia
• Alkalosis
• Injection of prostaglandins, arachidonic acid, hypo osmotic solutions,
calcium

38. Factors Affecting The Aqueous Out Flow
• Age : modest decline with age
• Hormones
– corticosteroid decrease
– progesterone,thyroxin ,prostaglandinsincrease
• Ciliary muscle tone: increased tone –increase
• Drugs : prostaglandin analogs, alpha2 agonists
• Surgical therapy: argon laser trabeculoplasty –improves;
cataract and PK reduces
• Diurnal fluctuation :controversy

39. References
• American Academy of Ophthalmology-sec 10
• Adler’s physiology of the Eye-9th edition
• Anatomy and physiology of eye -2nd edition