aqueous humour

AQUEOUS HUMOUR

ANATOMY AND PHYSIOLOGY

NETRADHAMA SCHOOL OF OPTOMETRY BSC 1ST YEAR

AQUEOUS HUMOUR

oThe Aqueous humour is involved with virtually all portions of the EyeCiliary body Posterior chamber Anterior chamberAngle of anterior chamberAqueous out-flow system

o Ciliary body

Ciliary body is the site of aqueous production

o Posterior chamber

Posterior chamber is a triangular space Containing 0.06 ml of aqueous humour

o Anterior chamber

Anterior chamber is small cavity line behind the cornea in front of iris

It contains 0.25 ml of aqueous humour 2.5 mm deep in centre

It is bounded by Anterior to posterior surface of cornea Posterior to anterior surface of ciliary body and iris Communicates through the pupil with posterior

chamber

o Angle Of Anterior Chamber

At the peripheral margin of anterior chamber is the corner between cornea , sclera , ciliary body and iris this is called the Angel of Anterior Chamber

Trabecular meshwork located in channel for the drainage of the aqueous from posterior to anterior chamber

Peripheral recess of anterior chamber Formed mainly by Trabecular meshwork Formed posterior to anterior by Ciliary band Scleral spur Teabecular meshwork Schwalbes line

Ciliary Band

• It is the most posterior structure formed by anterior most part of ciliary body between its attachment to the scleral spur and the insertion of iris .

Scleral spur

• It is the posterior portion of the scleral sulcus which usually appears as a prominent white line on gonioscopy • On it attached ciliary body posteriorly and

corneoscleral meshwork anteriorly

Trabecular meshwork

• It is seen as a band just anterior to the scleral spur

Schwalbes line

• It is fine rigid just in front of trabecular meshwork • It is formed by prominent Descemet membrane of

cornea

o Aqueous out-flow system

Aqueous humour is formed by ciliary processes of ciliary body in the posterior chamber

It flows between suspecially ligament of zonules and then through pupil into the anterior chamber

It includes the Trabecular meshwork Schlemm canal Collector channel Episcleral veins

Trabecular meshwork

• It is sieve like structure through which aqueous humour leves the eye. • It bridge the scleral sulcus and converted it into a tube ,

accommodates schlemms canal.• It consist of three parts Uveal meshwork Corneoscleral meshworkJuxtacanalicular meshwork (endothelial)

Uveal meshwork • it is innermost

part of trabecular meshwork extends form iris root and ciliary body through the schwalbes line .

• The trabecular of uveal meshwork are cord like and 2-3 layer thick .

Corneoscleral meshwork

• it forms the larger middle portion of the trabecular meshwork and extends from the scleral spur lateral wall of scleral sulcus

• It consist of flat sheet of trabeculae

Juxtacanalicular meshwork

• It forms the outermost portion of the trabecular meshwork and offers the normal resistance of the aqueous outflow

• It maintains the outflow of aqueous

• It consist a layer of connective tissue

• Inner endothelium contineous with cornea scleral meshwork

Schlemms Canal

• It is endothelial lined oval channel present in scleral sulcus • Endothelial of inner wall are irregular and contain giant

vacuoles • The outer wall of schlemms canal contains numerous

opeings of collector channel

Collector channel

• Their about 25-35 in number they leave the schlemms canal oblique angle to terminate into episcleral vein

Episcleral vein

• Most of the aqueous vescle drain into episcleral veins • Episcleral veins ultimately drain into cavernous sinus

via the anterior ciliary and superior ophthalmic veins

o Functions of Aqueous humour

Aqueous humour is a clear , colourless , watery solution , continuously circulate from the posterior camber of the eye throughout the anterior chamber

1. Maintainance of interocular pressure :- It is the primary function of the aqueous .

By virture of this , the aqueous humour helps in maintaining the shape and internal structural arrangement of the eye .

2 . Metabolic role :- In addition to its role in maintaining a proper intraocular pressure • Cornea :- Takes glucose and oxygen from the aqueous . • Lens :- uses oxygen , glucose , amino acid and

potassium from the aqueous .• Vitrous and retinal metabolism :- Is also appears to be

associated with the aqueous humour in that substance such as amino acid and glucose pass into the vetrious from the aqueous .

3 . Optical function :- Under normal condition aqueous is optically clear. the cornea – aqueous interface acts as a diverging lens of low power . 4 . Clearing function :- The aqueous humour serve as a mechanism to clear blood , macrophages , remnant of lens matter and products of inflammation from the anterior chamber of the eye .

o Physical Properties1. Total volume of the aqueous is 0.31ml * Anterior chamber 0.25ml * Posterior chamber 0.06ml .2 . Refractive index = 1.336 .3 . Density = 1.040 .4 . pH = aqueous is acidic with a pH in the anterior chamber of 7.2 .5 . Rate of formation = Normal aqueous 2.3 µl/min .6 . Osmotic pressure = Aqueous is slightly hyperosmotic to plasma by 3 to 5 mosm/l .

o Nerve supply

Both parasymphathetic and adrendrgic autonomic fibres and sensory fibres innervate the aquous outflow system .

o Aqueous humour outflow

Aqueous humour flows from posterior chamber into anterior chamber through pupil

From anterior chamber aqueous is drained out by two flows

Trabecular outflow Uveoscleral outflow

Trabecular Outflow :- Trabecular outflow is the main outlet

for aqueous from the anterior chamber • 75 to 90 % of the total aqueous is drained via this route • Free flow of aqueous occurs from the trabecular meshwork

in the angle of anterior chamber up to juxtacanalicular tissue , which along with the inner wall of schlemms canal to provide some resistance to the outflow .

Uveoscleral outflow :- It is responsible for some 10 – 25 % of the total aqueous outflow . • Aqueous passes across the ciliary body into the

suprachorodial space and is drained by the venous circulation in the ciliary body , choroid , sclera and into the orbital tissue