- Fluid present in eyeball.
- Responsible to maintain eyeball shape.
- Two types: a) Aqueous humor and b) Vitreous humor
- Fluid thin in nature present in front of retina.
- Space is present in between lens and cornea.
- Aqueous humor fills that space.
- The space also divides into anterior and posterior chamber.
- Iris divides the space into two chambers.
- Pupil helps to communicate both these chambers.
Image source: aao
Properties of Aqueous humor
- Volume of this fluid is 0.13 ml.
- It is alkaline in nature with pH 7.5.
- It has viscosity of 1.029.
- This fluid has refractive index of 1.34.
Composition of Aqueous humor
- It is composed of water and solids.
- Water makes 98.7% and solids make 1.3%.
- Solids contain different organic and inorganic substances.
- Albumin, globulin, glucose, lactate, pyruvate, urea present as organic substances.
- Calcium, sodium, magnesium, chlorides, potassium, bicarbonates, phosphates make inorganic part.
Image source: brainkart
Aqueous humor formation
- Ciliary processes forms this fluid.
- Plasma within capillary network of ciliary processes forms it.
- Diffusion, ultrafiltration and active transport are the involved process.
- Transport occurs through epithelial cells that lines ciliary processes.
- This fluid then passes through suspensory ligaments.
- From there, it reaches the posterior chamber.
- Fluid finally comes to anterior chamber via pupil.
- It is a continuous process i.e., formation of this fluid.
- In one minute, 2-3 µL of fluid is formed.
- In anterior chamber, this fluid is about 230-250 µL.
- 50-60 µL is the amount present in posterior chamber.
Drainage of aqueous humor
Anterior chamber → limbus (angle between cornea and iris) → meshwork of trabeculae → canal of schlemn →
→ anterior ciliary vein → venous system.
( meshwork of trabeculae – situated near the junction of iris and cornea)
Fig: flowchart of drainage of aqueous humor
Image source: mdpi
Functions of Aqueous humor
- Shape of eyeball maintained.
- Intraocular pressure maintained.
- Lens and cornea gets nutrients, oxygen and electrolytes.
(Lens and cornea are avascular structures)
- Lens and cornea contains metabolic end products.
- They are removed by this fluid.
- Fluid present in the space between lens and retina.
- Comprises 2/3rd of the eye volume.
- Hydrophilic, transparent, inert, colorless and gel structure.
- 99% of this fluid is water and 1 % is protein, sugars, salts, collagen, etc.
- Highly viscous and gelatinous, also called vitreous body.
- Fine fibrillar network of proteoglycan molecules forms this fluid.
- Albumin and hyaluronic acid are the major components.
- These substances enter the vitreous body from blood.
- Diffusion helps to transfer these substances.
Functions of vitreous humor
- Maintain the round shape of eyeball.
- Center of eyes remain clear so light can get to the retina and vision begins.
- Help in absorbing unexpected disturbances to the eye.
- Help to prevent eye damage.
- Pressure exerted by vitreous humor keeps the retina stable and in place.