Aqueous humour products and drainage

INTRODUCTIONThe clear fluid filling the space in front of the eyeball between lens and cornea.The aqueous humour supplies nutrition and removes waste from the clear structure in the anterior eye(cornea and lens)The balance between aqueous production and outflow determines the intraocular pressure.
INTRODUCTION
The clear fluid filling the space in front of the eyeball between lens and cornea.
The aqueous humour supplies nutrition and removes waste from the clear structure in the anterior eye(cornea and lens)
The balance between aqueous production and outflow determines the intraocular pressure.

1. AQUEOUS HUMOUR (PRODUCTION AND DRAINAGE) PRESENTER – FARHANA JAFRI MODERATOR – MR. JAYANT JHA

2. AQUEOUS HUMOUR INTRODUCTION The clear fluid filling the space in front of the eyeball between lens and cornea. The aqueous humour supplies nutrition and removes waste from the clear structure in the anterior eye(cornea and lens) The balance between aqueous production and outflow determines the intraocular pressure.

3. OCULAR STRUCTURES RELATED TO AQUEOUS HUMOUR Ciliary body Posterior chamber Anterior chamber Angle of the anterior chamber Aqueous outflow system

4. CILIARY BODY It is the site of aqueous humour production. It is the forward continuation of the choroid at ora serrata.

5. POSTERIOR CHAMBER It is a triangular space containing about 0.06 ml of aqueous humour production. It is bounded: Anteriorly by the posterior surface of iris and part of ciliary body. Posteriorly by the crystalline lens and its zonules. Laterally by the ciliary body.

6. ANTERIOR CHAMBER It is the fluid-filled space inside the eye between the iris and the cornea(endothelium). It is about 3 mm deep in normal adult. It contains about 0.25 ml of the aqueous humour production. It is filled by the clear fluid called aqueous humour.

7. ANTERIOR AND POSTERIOR CHAMBER

8. ANGLE OF THE ANTERIOR CHAMBER The peripheral recess of anterior chamber is called angle of anterior chamber. It is formed by the trabecular meshwork. It plays an important role in aqueous humour drainage.

9. STRUCTURE FORMING ANGLE RECESS 1. CILIARY BAND It is the most posterior landmark in the angle recess. It appears as a grey or dark brown band. 2 . SCLERAL SPUR It is the posterior portion of the scleral sulcus. It is usually appear as a prominent white line on gonioscopy.

10. CONT… 3. TRABECULAR MESHWORK It is seen as a band just anterior to the scleral spur. With age, its colour varies from faint tan to dark brown. 4. SCHWALBE’S LINE It is a fine ridge seen just in front of the trabecular meshwork.

11. GONIOSCOPIC GRADING OF THE ANGLE WIDTH Shaffer’s system of grading shows the angle width:

12. AQUEOUS OUTFLOW SYSTEM It includes: 1. Trabecular meshwork 2. Schlemm’s canal 3. Collector channel 4 . Episcleral vein

13. CONT… 1. TRABECULAR MESHWORK It is sieve-like structure through which aqueous humour leave the eye. It bridges the scleral sulcus and convert it into a tube, which accommodate schlemm’s canal. 2. SCHLEMM’S CANAL It is an endothelial lined oval channel. It is present in the scleral sulcus.

14. CONT… 3. COLLECTOR CHANNELS These are also called intrascleral aqueous vessels. It leave the schlemm’s canal at oblique angles to terminate ultimately into Episcleral vein. 4. EPISCLERAL VEINS Most of the aqueous vessels drain into the Episcleral vein.

15. PHYSIOCHEMICAL PROPERTIES 1. Volume:- 0.31 ml (0.25 ml in anterior chamber and 0.06 ml in posterior chamber). 2. Refractive Index:- 1.336 3. Osmotic Pressure:- 3-5 mOsm/l. 4. pH:- 7.2 5. Rate Of Formation:- 2.3 µl /min.

16. FUNCTIONS OF AQUEOUS HUMOUR It maintains the intraocular pressure (IOP ). It provides nutrition to cornea, lens, vitreous humour and retina . It removes harmful substances such as lactic acid and carbon dioxide . It provides optically clear medium for vision.

17. FORMATION OF AQUEOUS HUMOUR Aqueous humour is produced from pars plicata part of ciliary body through ciliary processes. Aqueous humour is derived from plasma within the capillary network of the ciliary processes. Three physiologic processes contribute to the formation of aqueous humour: 1. Diffusion 2. Ultrafiltration 3. Secretion

18. CONT…

19. 1. DIFFUSION Diffusion is the movements of substance across semipermeable membrane along concentration gradient. As aqueous humour passes from the posterior chamber to Schlemm’s canal, it is in contact with ciliary body, iris, lens, vitreous, cornea and trabecular meshwork. In the process of aqueous production, the lipid soluble substances are transported by diffusion through the lipid portion of the cell membrane of the ciliary processes.

20. CONT…

21. 2. ULTRAFILTRATION The process by which fluid and its solutes cross semipermeable membrane under pressure gradient is called ultrafiltration. It refers to occurrence of dialysis under hydrostatic pressure. In the process of aqueous formation, water and water-soluble substances flow through the protein part of the cell membrane in response to hydrostatic pressure.

22. CONT…

23. 3. SECRETION (ACTIVE TRANSFER) Secretion implies an active process that selectively transports some substances across the cell membrane. It is postulated that majority of aqueous humour formation depends on active transport. It is done by non-pigmented epithelial cells. This mechanism is mediated by globular proteins in the membrane and requires the expenditure of energy.

24. DRAINAGE OF AQUEOUS HUMOUR Aqueous flow from posterior to anterior chamber through pupil. From anterior chamber, the aqueous is drained out by two routes: 1. Trabecular (conventional) outflow 2. Uveoscleral (unconventional) outflow

25. FLOWCHART OF AQUEOUS HUMOUR DRAINAGE

26. CONT…

27. 1. TRABECULAR OUTFLOW The major drainage structure for aqueous humour are the conventional or trabecular outflow pathway. 75-90 % of the total aqueous is drained through this route. It is comprised of the trabecular meshwork (made by uveal and corneoscleral meshwork), the juxtacanalicular connective tissue (JCT), schlemm’s canal, collector channels and Episcleral vein. The TM outflow pathway is critical in providing resistance to aqueous humour outflow and in generating intraocular pressure (IOP).

28. CONT… Free flow of aqueous occurs from the trabecular meshwork in the angles of anterior chamber upto juxtacanalicular tissue. It along with the inner wall of the Schlemm’s canal appears to provide some resistance to the outflow.

29. 2. UVEOSCLERAL OUTFLOW The uveoscleral outflow is responsible for 10-25 % of the total aqueous humour outflow. Aqueous passes across the ciliary body into the suprachoroidal space. It is drained by the venous circulation in the ciliary body, choroid, sclera and into the orbital tissues. Uveoscleral outflow is approximately 0.3 ml.

30. CONT… The uveoscleral outflow is decreased by contraction and increased by relaxation of the ciliary muscles. Prostaglandins may decrease the intraocular pressure by increasing the uveoscleral outflow. Two mechanisms seem to contribute to this effect: relaxation of the ciliary muscle and changes in extracellular matrix, causing decreased resistance in the uveoscleral outflow routes.

31. REFERENCE ANATOMY AND PHYSIOLOGY 3 rd EDITION (AK KHURANA) GOOGLE

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