**3. Anterior chamber angle**

**Figure 3.** Histology of human ciliary epithelia

of epithelium. (FIGURE 3)

6 Glaucoma - Basic and Clinical Aspects

other.

**2. Ultrastructure of the ciliary processes**

um and contains mural cells or pericytes.

of connective tissue and the blood [11].

Each ciliary process is composed of a central stroma and capillaries, covered by a double layer

The ciliary process capillaries occupy the center of each process [10]. The capillary endothelium is thin and fenestrated, representing areas with fused plasma membranes and no cytoplasm, which may have an increased permeability. A basement membrane surrounds the endotheli‐

The stroma is very thin and surrounds the vascular tissues, separating them from the epithelial layers. The stroma is composed of ground substance (mucopolysaccharides, proteins and plasma of low molecular size), collagen connective tissue (especially collagen type III) and cells

Ciliary process epithelia consist of two layers, with the apical surfaces in apposition to each

The pigmented epithelium is the outer layer, and the cuboidal cells contain numerous melanin granules in their cytoplasm. This layer is separated from the stroma by an atypical basement membrane, a continuation of Bruch`s membrane which contains collagen and elastic fibers [15]. The nonpigmented epithelium is composed of columnar cells with numerous mitochondria, well-developed endoplasmic reticulum seen in the cytoplasm, extensive infoldings of the membranes and tight junctions between the apical cell membranes. The basement membrane The iris inserts into the anterior side of the ciliary body and separates the aqueous compartment into a posterior and anterior chamber. The angle formed by the iris and the cornea is the anterior chamber angle6 .

The aqueous humor is formed by the ciliary process, passes from posterior chamber to the anterior chamber through the pupil, and leaves the eye at the anterior chamber angle. Most of the aqueous humor exits the eye through the trabecular meshwork, which is called the conventional or canalicular system, and accounts for 83 to 96% of aqueous outflow of normal human eyes [21,22].

The other 5-15% of the aqueous humor leaves the eye through the uveoscleral and uveovortex systems (unconventional systems), including anterior ciliary muscle and iris to reach supra‐ ciliary and suprachoroidal spaces [22,23,24].

#### **3.1. Anatomy of anterior chamber angle (conventional outflow system)**

#### **a.** Schwalbe`s line

This line or zone represents the transition from the trabecular to corneal endothelium, the termination of Descemet`s membrane, and the trabecular insertion into the corneal stroma.

Schwalbe`s line is just anterior to the apical portion of the trabecular meshwork, is composed of collagen and elastic tissue and has a width that varies 50-150 µm; it has been called Zone S [25].

The perforations are elliptical and become progressively smaller from the uveal meshwork to the deep layers of the corneoscleral meshwork [28]. The aqueous humor leaves the trabecular in a tortuous route until reaching Schlemm´s canal, because the perforations are not aligned.

ripheral corne al trabeculae, c wide perforati ral meshwork heets are not v and become pr umor leaves

ea. These stra ciliary fibers, ions.

Anatomy of Ciliary Body, Ciliary Processes, Anterior Chamber Angle and Collector Vessels

ands are a nor and uveocorn

rmal variant a neal fibers. Th

http://dx.doi.org/10.5772/52780

and are called he deeper laye

9

by a variety ers of the uve

names such a oscleral mesh

as iris hwork

to the

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entric layer ich is layer y gap n and

red is

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of four conce in. There is a embrane, whi a continuous y are joined by nts (vimentin

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is composed d III and elasti by a glass me thelial layer is lial cells. They ediate filamen

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shwork to the ntil reaching

r. Each sheet er types I and surrounded b d V. The endot rneal endothel s and interme

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the uveal mes uous route un

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to 15 perforate copically.

smaller from t ar in a tortu

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cornea and mo

ody to the pe d fibers, uvea d sheets with w the corneoscle spur. These sh are elliptical a e aqueous hu ot aligned.

e of the trabe ular beams ha stic fibers tha onectin, lamini trabeculae. Th ght junctions

**opy of the n**

tarting at the c FIGURE 4)

The ultrastructure of the trabecular, uveal and corneoscleral meshworks is similar. Each sheet is composed of four concentric layers. The trabecular beams have a central core of connective tissue of collagen fiber types I and III and elastin. There is a layer composed of elastic fibers that provides flexibility to the trabeculae. The core is surrounded by a glass membrane, which is composed of fibronectin, laminin, heparin, proteoglycan and collagen type III, IV and V. The endothelial layer is a continuous layer and covers all the trabeculae. The endothelial cells are larger, more irregular than corneal endothelial cells. They are joined by gap junctions and tight junctions and have microfilaments, including actin filaments and intermediate filaments

On gonioscopy, starting at the cornea and moving posteriorly toward the root of the iris, the

(vimentin and desmin) [30].

**3.2. Gonioscopy of the normal anterior chamber angle**

**Goniosco**

gonioscopy, st walbe´s line. (F

**3.2.**

On g Schw

Figur Schw mesh It ca goni to id The anter poste of fib varie depe

anterior extension of the trabecular meshwork.

between the cornea and the meshwork).

re 4. Normal go walbe´s line co hwork.

**Figure 4.** Normal gonioscopic vision of Schwalbe´s line (black arrow)

onioscopic visio orresponds to

on of Schwalbe´s the terminati

s line (black arr ion of Descem

ow)

met´s membran

ne and marks

the most ant

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red as two sep not visible g hwork compos bution of the p age from ligh

the meshwork of the cornea c

ay be conside meaning it is abecular mesh unt and distrib s color with

anterior to t terior beams o

pur, and it ma pigmented, m pigmented tra ace. The amou and develop angle.

te ridge, just erior and post work).

d the scleral s s and is not ow and is the p gmented surfa no pigment, erior chamber

as a fine whit where the ante and the meshw albe´s line and oscleral sheets queous outflo roughened pig birth, it has ion in the ante

xamination, a d at the point w en the cornea a between Schw sed of corneo mary site of aq s an irregular r and race. At ment dispersi

Schwalbe´s line corresponds to the termination of Descemet´s membrane and marks the most

It can be seen, by slit-lamp examination, as a fine white ridge, just anterior to the meshwork, and with an indirect contact gonioscopic lens, it is identified at the point where the anterior and posterior beams of the cornea converge (parallelepiped method to identify the transition

y slit‐lamp ex it is identified nsition betwee eshwork lies b ich is compo hich is the prim opically, it has ly with age a degree of pigm

an be seen, by oscopic lens, i dentify the tran trabecular me rior part, whi erior part, wh bers. Goniosco es considerab ending on the

root proc are m The o scler The mesh perfo The layer comp comp and junct desm

and ciliary bo ess, pectinate more flattened outer layers, t ral sulcus and perforations a hwork[28]. The orations are no ultrastructure rs. The trabec posed of elas posed of fibro covers all the tions and tig min)[30].

first anatomic structure encountered is Schwalbe´s line. (FIGURE 4)

#### **b.** Scleral spur

The posterior wall of the scleral sulcus is formed by a group of fibers, parallel to the limbus that project inward like a fibrous ring, called the scleral spur. These fibers are composed of 80% collagen (collagen type I and III) and 5% elastic fibers. The spur is attached anteriorly to the trabecular meshwork and posteriorly to the sclera and the longitudinal portion of the ciliary muscle [26].

When the ciliary muscle contracts, it pulls the scleral spur posteriorly, it increases the width of the intertrabecular spaces and prevents Schlemm`s canal from collapsing [27].

**c.** Ciliary body band

This is structure that is located posterior to scleral spur.

When the iris inserts into the anterior side of the ciliary body, it leaves a variable width of the latter structure visible between the iris and scleral spur, corresponding to the ciliary body band. Gonioscopically, it appears as a brownish band.

**d.** Trabecular meshwork

The aqueous humor leaves the eye at the anterior chamber angle through the conventional system consisting of the trabecular meshwork, Schlemm´s canal, intrascleral channels, and episcleral and conjunctival veins.

The trabecular meshwork consists of connective tissue surrounded by endothelium. In a meridional section, it has a triangular shape, with the apex at Schwalbe´s line and the base at the scleral spur.

The meshwork consists of a stack of flattened, interconnected, perforated sheets, which run from Schwalbe´s line to the scleral spur. This tissue may be divided into three portions: a) uveal meshwork, b) corneoscleral meshwork and c) juxtacanalicular tissue6 . By gonioscopy, the trabecular meshwork can be separated into two portions: an anterior (named non-pigmented) and a posterior (pigmented).

The inner layers of the trabecular meshwork can be observed in the anterior chamber angle and are referred to as the uveal meshwork. This portion is adjacent to the aqueous humor, is arranged in bands or rope-like trabeculae, and extends from the iris root and ciliary body to the peripheral cornea. These strands are a normal variant and are called by a variety names such as iris process, pectinated fibers, uveal trabeculae, ciliary fibers, and uveocorneal fibers. The deeper layers of the uveoscleral meshwork are more flattened sheets with wide perforations.

The outer layers, the corneoscleral meshwork, consist of 8 to 15 perforated sheets. The corneoscleral trabecular sheets insert into the scleral sulcus and spur. These sheets are not visible gonioscopically.

The perforations are elliptical and become progressively smaller from the uveal meshwork to the deep layers of the corneoscleral meshwork [28]. The aqueous humor leaves the trabecular in a tortuous route until reaching Schlemm´s canal, because the perforations are not aligned. root proc are m and ciliary bo ess, pectinate more flattened ody to the pe d fibers, uvea d sheets with w ripheral corne al trabeculae, c wide perforati ea. These stra ciliary fibers, ions. ands are a nor and uveocorn rmal variant a neal fibers. Th and are called he deeper laye

The ultrastructure of the trabecular, uveal and corneoscleral meshworks is similar. Each sheet is composed of four concentric layers. The trabecular beams have a central core of connective tissue of collagen fiber types I and III and elastin. There is a layer composed of elastic fibers that provides flexibility to the trabeculae. The core is surrounded by a glass membrane, which is composed of fibronectin, laminin, heparin, proteoglycan and collagen type III, IV and V. The endothelial layer is a continuous layer and covers all the trabeculae. The endothelial cells are larger, more irregular than corneal endothelial cells. They are joined by gap junctions and tight junctions and have microfilaments, including actin filaments and intermediate filaments (vimentin and desmin) [30]. The o scler The mesh perfo The layer comp comp and outer layers, t ral sulcus and perforations a hwork[28]. The orations are no ultrastructure rs. The trabec posed of elas posed of fibro covers all the the corneoscle spur. These sh are elliptical a e aqueous hu ot aligned. e of the trabe ular beams ha stic fibers tha onectin, lamini trabeculae. Th ral meshwork heets are not v and become pr umor leaves ecular, uveal a ave a central t provides fle in, heparin, pr he endothelia k, consist of 8 t visible goniosc rogressively s the trabecula and corneoscl core of conne exibility to th roteoglycan an al cells are larg to 15 perforate copically. smaller from t ar in a tortu leral meshwo ective tissue of he trabeculae. nd collagen ty ger, more irreg ed sheets. The the uveal mes uous route un orks is similar f collagen fibe The core is ype III, IV and gular than cor e corneosclera shwork to the ntil reaching r. Each sheet er types I and surrounded b d V. The endot rneal endothel

#### **3.2. Gonioscopy of the normal anterior chamber angle** desm min)[30].

tions and tig

walbe´s line. (F

junct

Schw

Schwalbe`s line is just anterior to the apical portion of the trabecular meshwork, is composed of collagen and elastic tissue and has a width that varies 50-150 µm; it has been

The posterior wall of the scleral sulcus is formed by a group of fibers, parallel to the limbus that project inward like a fibrous ring, called the scleral spur. These fibers are composed of 80% collagen (collagen type I and III) and 5% elastic fibers. The spur is attached anteriorly to the trabecular meshwork and posteriorly to the sclera and the longitudinal portion of the ciliary

When the ciliary muscle contracts, it pulls the scleral spur posteriorly, it increases the width

When the iris inserts into the anterior side of the ciliary body, it leaves a variable width of the latter structure visible between the iris and scleral spur, corresponding to the ciliary body band.

The aqueous humor leaves the eye at the anterior chamber angle through the conventional system consisting of the trabecular meshwork, Schlemm´s canal, intrascleral channels, and

The trabecular meshwork consists of connective tissue surrounded by endothelium. In a meridional section, it has a triangular shape, with the apex at Schwalbe´s line and the base at

The meshwork consists of a stack of flattened, interconnected, perforated sheets, which run from Schwalbe´s line to the scleral spur. This tissue may be divided into three portions: a) uveal

trabecular meshwork can be separated into two portions: an anterior (named non-pigmented)

The inner layers of the trabecular meshwork can be observed in the anterior chamber angle and are referred to as the uveal meshwork. This portion is adjacent to the aqueous humor, is arranged in bands or rope-like trabeculae, and extends from the iris root and ciliary body to the peripheral cornea. These strands are a normal variant and are called by a variety names such as iris process, pectinated fibers, uveal trabeculae, ciliary fibers, and uveocorneal fibers. The deeper layers of the uveoscleral meshwork are more flattened

The outer layers, the corneoscleral meshwork, consist of 8 to 15 perforated sheets. The corneoscleral trabecular sheets insert into the scleral sulcus and spur. These sheets are not

. By gonioscopy, the

meshwork, b) corneoscleral meshwork and c) juxtacanalicular tissue6

of the intertrabecular spaces and prevents Schlemm`s canal from collapsing [27].

This is structure that is located posterior to scleral spur.

Gonioscopically, it appears as a brownish band.

called Zone S [25].

8 Glaucoma - Basic and Clinical Aspects

**b.** Scleral spur

muscle [26].

**c.** Ciliary body band

**d.** Trabecular meshwork

the scleral spur.

episcleral and conjunctival veins.

and a posterior (pigmented).

sheets with wide perforations.

visible gonioscopically.

On gonioscopy, starting at the cornea and moving posteriorly toward the root of the iris, the first anatomic structure encountered is Schwalbe´s line. (FIGURE 4) **3.2.** On g **Goniosco** gonioscopy, st **opy of the n** tarting at the c **normal an** cornea and mo **nterior cham** oving posterio **mber angl** orly toward th **le** he root of the ir ris, the first an

and have mi

icrofilaments,

including ac

ctin filaments

s and interme

by a variety ers of the uve

names such a oscleral mesh

as iris hwork

to the

cleral e the

entric layer ich is layer y gap n and

red is

heets insert int

of the corneos canal, because

of four conce in. There is a embrane, whi a continuous y are joined by nts (vimentin

ture encounter

l trabecular sh

deep layers o Schlemm´s c

is composed d III and elasti by a glass me thelial layer is lial cells. They ediate filamen

natomic struct

erior extensio

on of the trabe

ecular

ontact ethod

ns: (a) y; (b) ytium sition rown,

an indirect co allelepiped me

parate portion gonioscopically sed of a syncy pigment depos ht to dark br

k, and with a converge (para

red as two sep not visible g hwork compos bution of the p age from ligh

s line (black arr

ow)

gmented surfa no pigment, erior chamber

ace. The amou and develop angle.

unt and distrib s color with

roughened pig birth, it has ion in the ante

ght junctions

FIGURE 4)

Figur re 4. Normal go onioscopic visio on of Schwalbe´s **Figure 4.** Normal gonioscopic vision of Schwalbe´s line (black arrow)

of fib varie depe

bers. Goniosco es considerab ending on the

Schw mesh It ca walbe´s line co hwork. an be seen, by orresponds to y slit‐lamp ex the terminati xamination, a ion of Descem as a fine whit met´s membran te ridge, just ne and marks anterior to t the most ant the meshwork Schwalbe´s line corresponds to the termination of Descemet´s membrane and marks the most anterior extension of the trabecular meshwork.

goni to id The anter poste oscopic lens, i dentify the tran trabecular me rior part, whi erior part, wh it is identified nsition betwee eshwork lies b ich is compo hich is the prim d at the point w en the cornea a between Schw sed of corneo mary site of aq where the ante and the meshw albe´s line and oscleral sheets queous outflo erior and post work). d the scleral s s and is not ow and is the p terior beams o pur, and it ma pigmented, m pigmented tra of the cornea c ay be conside meaning it is abecular mesh It can be seen, by slit-lamp examination, as a fine white ridge, just anterior to the meshwork, and with an indirect contact gonioscopic lens, it is identified at the point where the anterior and posterior beams of the cornea converge (parallelepiped method to identify the transition between the cornea and the meshwork).

> s an irregular r and race. At ment dispersi

opically, it has ly with age a degree of pigm The trabecular meshwork lies between Schwalbe´s line and the scleral spur, and it may be considered as two separate portions: (a) anterior part, which is composed of corneoscleral sheets and is not pigmented, meaning it is not visible gonioscopically; (b) posterior part, which is the primary site of aqueous outflow and is the pigmented trabecular meshwork composed of a syncytium of fibers. Gonioscopically, it has an irregular roughened pigmented surface. The amount and distribution of the pigment deposition varies considerably with age and race. At birth, it has no pigment, and develops color with age from light to dark brown, depending on the degree of pigment dispersion in the anterior chamber angle.

**6. Collector channels**

ophthalmic veins.

palpebral veins [37].

**Author details**

**References**

the episcleral venous system [34,35].

**7. Episcleral and conjunctival veins**

Adriana Silva Borges- Giampani and Jair Giampani Junior

Federal University of Mato Grosso, Brazil

edition,(1999). , 20-64.

WB Saunders,269; (1971).

Ophthalmology 88: 283, (1981).

Schlemm`s canal drains into the episcleral and conjunctival veins by a complex system of vessels (collector channels or outflow channels). This system is composed of innumerous intrascleral aqueous vessels and aqueous veins of Ascher, which arise from the outer wall of Schlemm`s canal up to the episcleral and conjunctival veins. These collector vessels can run like a direct system, draining directly into the episcleral venous system or like an indirect system of more numerous, fine channels, forming an intrascleral plexus before draining into

Anatomy of Ciliary Body, Ciliary Processes, Anterior Chamber Angle and Collector Vessels

http://dx.doi.org/10.5772/52780

11

The aqueous humor reaches the episcleral venous system by several routes [36]. Most aqueous vessels run posteriorly draining into episcleral and conjunctival veins. Some aqueous vessels

The episcleral veins drain into the cavernous sinus by the anterior ciliary and superior

The conjunctival veins drain into superior ophthalmic or facial veins via the angular or

[1] Stamper, R. L, Lieberman, M. F, & Drake, M. V. Aqueous Humor Formation and Outflow. In Diagnosis and Therapy of the glaucomas. Becker-Shaffer`s. Mosby, Seventh

[2] Hogan, M. F, Alvarado, J. A, & Weddell, J. E. Histology of the Human Eye. Philadelphia,

[3] Smelser GK; Electron microscopy of a typical epithelial cell and of the normal human

[4] Brubaker, R. F. and cols; The effect of age on aqueous humor formation in man,

ciliary processTrans Am Acad Ophthalmol Otolaryngol 70: 738,(1966).

run parallel to the limbus before heading posteriorly toward the conjunctival veins.

The scleral spur is just posterior to the pigmented trabecular band, and it is the most anterior projection of the sclera internally. Gonioscopically, it is seen as a prominent white line between the ciliary body band and pigmented trabecular. It can be obscured by excessive pigment dispersion, and is not visible at variable degrees of narrow or occluded angles.

The iris processes, thickenings of the posterior uveal meshwork, may be frequently seen crossing the scleral spur. They have the appearance of a variable number of fine and pigmented strands.

The ciliary body band is the portion of ciliary body that is visible in the anterior chamber. The width of the band depends on the point of the iris insertion on the ciliary body. Gonioscopi‐ cally, it appears as a densely pigmented band, gray or dark-brown, posterior to the scleral spur and anterior to the root of the iris.
