Anterior Chamber Study Answers

what are the boundaries of the anterior chamber

anterior - posterior surface of cornea

posterior - anterior border layer of iris and anterior surface of lens at the pupil

lateral- face of CB. trabecular meshwork and angle structures

anterior boundary of anterior chamber

posterior surface of cornea

posterior boundary of anterior chamber

anterior border layer of iris and anterior surface of lens at the pupil

lateral boundary of anterior chamber

face of CB. trabecular meshwork and angle structures

volume of anterior chamber

250 uL

shape of anterior chamber

ellipsoid

whats the angle of the anterior chamber

where iris and cornea meet

what is the depth of the anterior chamber

3.5 - 3.7 mm (apex of cornea to lens)

what is the diameter of the anterior chamber

11.3 to 12.4 mm

how does the anterior chamber angle openness vary by age

narrows as we age due to thickening of lens

how does the anterior chamber angle openness vary by heredity

inherit openness of the angle

how does the anterior chamber angle openness vary by refractive error

myopes - more open angle

hyperope - more narrow angle

how does the anterior chamber angle openness vary by race

Asians – more narrow angles

Blacks – more open angles

how does the anterior chamber angle openness vary by gender

males - larger than females

what are the major fxns of the anterior chamber angle

1. pathway for aqueous to exit the eye

2. self-cleaning filter - phagocytosis

3. rectifying properties - allows for one-way flow of aq our of the angle and into schlemms canal

what are the two major pathways for aq to exit the eye

1. conventional pathway - trabecular meshwork

2. uvoscleral pathway

which pathway for aq exiting the eye accounts for the highest volume of outflow

conventional pathway - 80%

what is the ultrastructure of the trabecular meshwork

1. collagen core

   1. type I (tensile)

   2. type III (resilience)

2. elastic fibers surround collagen - allows for reversible deformation

3. core is surrounded by proteoglycans and that is covered by an endothelium

describe uveal meshwork

1. cords of meshowrk - 2-3 layers

2. large intertrabecular spaces

3. adjacent to anterior chamber

uveal meshwork fxn

gross filtration

describe corneoscleral meshwork

1. sheets of meshwork w pores - approx 20 sheets

2. pores get smaller as we get closer to schlemms canal

   1. pores run thru endothelial cells that line the meshwork

corneoscleral meshwork fxn

finer filtration

describe the anterior trabecular meshwork

Most anterior portion of meshwork

–considered non-filtering portion of meshwork

composition of Schwalbe’s line

1. most anterior structure of the angle

   1. transition between TM and endothelium of cronea (Descemets membrane ends)

2. circumferential ring of collagen and elastin

3. pigmented Schwalbe’s line - Sampaolesi’s line

4. thickened and anteriorly displaced Schwalbe’s line - posterior embryotoxon

composition of Scleral spur

1. circumferential scleral fibers that are adjacent to Schlemms canal

2. histology is similar to sclera stroma except it contains a few more elastin fibers

what attaches to the scleral spur

TM and CB fibers

how does the corneal endothelium compare to the trabecular meshwork endothelium

1. both are metabolically active

2. neither exhibit mitosis under normal conditions

   1. TM may have limited mitosis after laser tx

3. both increase in size w age

4. both decrease in number w age

5. different fxns

how does trabecular meshowrk carry out its function as a self cleaning filter

1. engulfs and ingests debris from TM - phagocytosis

what are the “smooth muscle” properties of the TM endothelial cells and how could these properties be used to lower intraocular pressure

1. TM endothelial cells have a large number of transporters, channels, and receptors which are known to regulate smooth muscle

2. also have contractile like properties

3. mech

   1. rho kinase inhibitors relax TM endothelial cells to relax and open the meshwork to lower IOP

   2. rho kinase inhibitors also enhance episcleral outflow

composition of the juxtacanalicular tissue

1. collagen fibers

2. high conc of GAGs

how does the composition of the juxtacanalicular tissue slow the flow of aq

1. very viscous env slows flow of aq

2. JCT offers the greatest resistance to the outflow of aq

what is the fxn of the juxtacanalicular cells

1. produce extracellular substances - GAGs

2. sends out cytoplasmic proceses to attach to inner wall of Schlemm’s canal as well as to the corneoscleral TM

   1. this prevents separation of Schlemms canal from TM during changes in IOP

what is the juxtacanalicular tissue/ cribriform plexus

1. consists of elastic like fibers that connect the juxtacanalicular tissue and the inner wall of Schlemms canal to the longitudinal muscle fibers of CB

how does contraction of the CB affect the juxtacanalicular tissue, aq outflow, and intraocular pressure

With contraction of the ciliary muscle, the outflow of aqueous is enhanced through the JCT and the inner wall of Schlemm’s canal.

This helps to lower IOP

what is the size and location of Schlemms canal

1. oval shaped lymphoid like sinus

2. runs 360 degrees in the internal scleral sulcus

3. has a circumference of 36 mm

characteristics of the inner wall of schlemms canal and how they affect aq outflow

1. ultrastructure of the endothelial cells includes:

   1. discontinuous zonula occludens

2. some aq flows via pinocytosis

3. creates a pressure gradient on the inner wall of the canal and slows down the flow of aqueous outflow

how does most of the aq enter schlemms canal via the inner wall? How do the giant vacuolse prevent the regurgitation of aq back into schlemms canal

1. the endothelial cells that line the inner wall of schlemms canal form giant vacuoles in response to increased pressure

2. vacuoles open on the lumen side of the canal to release the aq in a 1 way direction

   1. this prevents regurgitation of aq back into the TM

3. the higher the pressure, the more vacuoles form to move more aq into Schlemms canal

   1. PRESSURE DEPENDENT SYSTEM

fxn of Sondermanns afferent or internal collector channels

1. out pouchings of the innr of schlemms canal that function to increase SA for more giant vacuole formation

where do the external or efferent collector channels connect to and where do they ultimately drain

1. exit via the outer wlal of schelmms canal

2. drain into aq veins or into several venous plexi which drain into episcleral veins that ultimately drain into ophthalmic veins

how do we get blood from episcleral veins into Schlemms canal

1. theres not a direct connection between the venous system and schlemms canal

2. pressure on the venous system can cause regurgitaiton of blood back into the canal

   1. short term: not a clinical problem

      1. excessive pressure via a 3 mirror gonio lens

   2. long term blood in Schlemms canal: can cause secondary glaucoma

why does the blood in schlemms canal (bc of pressure on the venous system) not enter the anterior chamber aq

1. Blood does not enter the anterior chamber because of the zonula occludens of the inner wall of Schlemm’s canal

2. and because of the one-way system of aqueous outflow (giant vacuoles).

aq flow thru uveoscleral pathway

Aqueous enters face of ciliary body or anterior border layer of iris -> between ciliary muscle fibers -> supraciliary space - > vortex veins