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1. PAS (Peripheral Anterior Synechia)

PAS is adhesions between the iris and posterior surface of the cornea. ccc Today, peripheral

anterior synechiae are a well-recognized consequence of altered anterior

chamber (AC) anatomy and anterior chamber inammation. !eripheral anterior

synechiae can subsequently result in signi"cant morbidity as a precipitant to

secondary angle-closure glaucoma.

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Pathophysiology

Peripheral anterior synechiae may form under the following 2 circumstances: a nonproliferative state or a

proliferative state.

Apposition of the iris against the trabecular meshwor as a result of pupil bloc or a posterior pushing

mechanism without any inflammation can result in continuous peripheral anterior synechiae. !hese

continuous peripheral anterior synechiae lead to "#ippering" of the angle. Primary angle$closure glaucoma

and the various posterior pushing mechanisms are e%amples of this process.

&n the presence of inflammation or cellular proliferation' a membrane forms between the iris and the

trabecular meshwor' creating the peripheral anterior synechiae. !his membrane contracts' resulting in

angle$closure glaucoma by an anterior pulling mechanism. %amples of this process include the

fibrovascular membrane formed in neovascular glaucoma' proliferating abnormal endothelial cells in the

iridocorneal endothelial (&) syndromes' epitheliali#ation of the angle due to epithelial ingrowth' or inflammatory trabecular and eratic precipitates in contact with an inflamed iris. !hese processes can be

accentuated by iris swelling and protein transudation and e%udation.

Physical

As a general principle' e%amination of the nonaffected eye in unilateral presentations may prove to be

valuable in trying to discern between primary and secondary etiologies of angle closure.

• *efraction: +yperopia is a ris factor for angle closure.

• ,onioscopy

o -eiss compression

-eiss compression should be performed to distinguish appositional closure from

synechial closure in narrow$angle glaucoma.

Areas where an abrupt change in the angle from open to closed is present suggest

the presence of peripheral anterior synechiae.

&f not visuali#ed directly' synechial presence can be indicated by the lac of

displacement of the focal lines reflected from the posterior surface of the cornea

and the anterior surface of the iris. hen peripheral anterior synechiae are not

present' a displacement will be noted with compression gonioscopy.

&t is imperative that the entire circumference of the angle be e%amined for an

open' normal$looing angle and compared to the regions of peripheral anterior

synechiae to estimate the filtration capabilities of the eye.


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!he point of anterior attachment of peripheral anterior synechiae should be noted

because peripheral anterior synechiae that obstruct the central third of the

trabecular meshwor are more liely to result in increased intraocular pressure.

!able 1. /escription of PAS on gonioscopy (0pen !able in a new window)

• Prominent uveal meshwor (must be differentiated from peripheral anterior synechiae)

o an be confused for peripheral anterior synechiae

o ore common and e%tensive in brown irides compared to blue eyes

o +as a lacy and porous appearance through which angle structures can be visuali#ed this

can be enhanced with transillumination

o A%enfeld and *ieger anomalies (anterior segment dysgenesis) may have anterior

prominent uveal meshwor with an anterior displaced Schwalbe line' which is not

believed to be true peripheral anterior synechiae.

• ornea

o 3eratic precipitates would indicate an inflammatory etiology.

o Polymorphous opacities at the /escemet membrane level suggest posterior

polymorphous dystrophy (PP/).

o orneal guttata and4or edema are suggestive of handler syndrome.

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o ongenital corneal opacities or sclerocornea suggest a congenital corneal defect (anterior

segment dysgenesis).

o Posterior embryoto%on

• Anterior chamber depth

o &f the peripheral depth in this region has a corneal thicness of one fourth or less' the

possibility of angle closure e%ists (5on +erric law).

o /istinction should be made between peripheral and central shallowing.

o Pupil bloc commonly results in greater peripheral shallowing as compared to the central

anterior chamber.

o Posterior pushing mechanisms result in e6ual peripheral and central shallowing.

• &ris

o &ris atrophy may suggest previous attacs of angle$closure glaucoma' uveitis' or anterior

segment dysgenesis.

o 3oeppe and 7usacca nodules suggest iritis.

o &rregularity of the pupil may be secondary to trauma or inflammation.

o 8ew vessels along the anterior iris stroma and ectropion uveae suggest neovascular

glaucoma.

o ctropion uveae' corectopia' iris stretch holes' and nevi suggest an iridocorneal

endothelial syndrome.

o Anterior bowing of the iris may imply an element of pupil bloc or iris bomb9.

• ens

o ,lauomflecen suggests previous attacs of angle$closure glaucoma.

o Pseudoe%foliation is associated with #onule la%ity' which can result in forward

displacement of the lens.

o Posterior synechiae may lead to iris bomb9.

o &ntumescent lens may cause shallowing of the anterior chamber.

• *etina


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o Any cause of vascular compromise (eg' diabetic retinopathy' central retinal artery

occlusion ;*A0veitis

Pupil bloc

!rauma Primary angle$closure glaucoma

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&nflammatory syndromes

&nfectious

ens related

Posterior synechiae resulting in iris

bomb9

Pseudophaic or aphaic pupil bloc

&ridoschisis

?lat anterior chamber Plateau iris

Posterior pushing

Postsurgical

!rauma

horoidal effusion

$Posterior uveitis

$*50

$8anophthalmos

$Post$pan retinal photocoagulation(P*P) or cryotherapy

Suprachoroidal hemorrhage

iliary bloc (malignant) glaucoma

(a6ueous misdirection)


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Posterior segment tumors

$*etinoblastoma

$horoidal melanoma or metastasis

&ris cyst or tumor

iliary body cyst' tumor' or effusion

ontracting retrolental tissue

$*etinopathy of prematurity

$Persistent hyperplastic primary vitreous

(P+P5)

Postscleral bucing surgery

Anterior lens sublu%ation (ectopia lentis)

ens intumescence (phacomorphic)

8eurofibromatosis


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Argon laser trabeculoplasty

2. Anatomy of iliar 7ody

!he ciliary body is the site of a6ueous humor production and it is totally involved in a6ueous

humor dynamics. !he ciliary body is the anterior portion of the uveal tract' which is located

between the iris and the choroid. (figure 1)

Figure 1. +istology of human ciliary body (courtesy Prof. *uth Santo)

0n cross$section' the ciliary body has the shape of a right triangle' appro%imately @ mm in

length' where its ape% is contiguous with the choroid and the base close to the iris. %ternally' it

attaches to the scleral spur creating a potential space' the supraciliary space' between it and the

sclera. !he e%ternal surface forms the anterior insertion of the uveal tract. !he internal surface of

the ciliary body comes in contact with the vitreous surface and is continuous with the retina ;1


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!he pars plicata is contiguous with the iris posterior surface and is appro%imately 2 mm in

length' B.D mm in width' and B.E$1 mm in height ;2'F


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supracoroidal lamina (fibers connecting choroid and sclera) as far bac as the e6uator of the eye

;@


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!he maCor innervation is provided by ciliary nerve branches (third cranial nerve$oculomotor)'

forming a rich parasympathetic ple%us. !here are also sympathetic fibers originating from the

superior cervical ganglion which eep pace with arteries and their branches.

Figure 3. +istology of human ciliary epithelia

Ultrastructure of the ciliary processes

ach ciliary process is composed of a central stroma and capillaries' covered by a double layer

of epithelium. (?&,>* F).!he ciliary process capillaries occupy the center of each process ;1B


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!he pigmented epithelium is the outer layer' and the cuboidal cells contain numerous melanin

granules in their cytoplasm. !his layer is separated from the stroma by an atypical basement

membrane' a continuation of 7ruchJs membrane which contains collagen and elastic fibers ;1D


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the conventional or canalicular system' and accounts for EF to K@G of a6ueous outflow of normal

human eyes ;21'22


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and conCunctival veins. !he trabecular meshwor consists of connective tissue surrounded by

endothelium. &n a meridional section' it has a triangular shape' with the ape% at SchwalbeNs line

and the base at the scleral spur.

!he meshwor consists of a stac of flattened' interconnected' perforated sheets' which run from

SchwalbeNs line to the scleral spur. !his tissue may be divided into three portions: a) uveal

meshwor' b) corneoscleral meshwor and c) Cu%tacanalicular tissue@. 7y gonioscopy' the

trabecular meshwor can be separated into two portions: an anterior (named non$pigmented)

and a posterior (pigmented).

!he inner layers of the trabecular meshwor can be observed in the anterior chamber angle and

are referred to as the uveal meshwor. !his portion is adCacent to the a6ueous humor' is arranged

in bands or rope$lie trabeculae' and e%tends from the iris root and ciliary body to the peripheral

cornea. !hese 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. !he deeper layers of the

uveoscleral meshwor are more flattened sheets with wide perforations.

!he outer layers' the corneoscleral meshwor' consist of E to 1D perforated sheets. !he

corneoscleral trabecular sheets insert into the scleral sulcus and spur. !hese sheets are not

visible gonioscopically. !he perforations are elliptical and become progressively smaller from

the uveal meshwor to the deep layers of the corneoscleral meshwor ;2E


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Cunctions and have microfilaments' including actin filaments and intermediate filaments

(vimentin and desmin) ;FB


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posterior chamber to anterior chamber ( seclusio pupillae). !hus' the a6ueous collects

behind the iris and pushes it anteriorly (leading to ‘iris-bombe’ formation) . !his is

usually followed by a rise in intraocular pressure.

3. Total posterior synechiae due to plastering of total posterior surface of iris with the

anterior capsule of lens are rarely formed in acute plastic type of uveitis. !hese result

in deepening anterior chamber.


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