Peripheral Anterior Synechia

Peripheral Anterior Synechia

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Peripheral anterior synechiae (PAS), which were first described by Barkan in 1938, are adhesions between the iris and trabecular meshwork. PAS may reduce outflow of aqueous humor and may lead to raised intraocular pressure.

PAS result from prolonged appositional contact between the iris and trabecular meshwork (as in primary angle closure) or from anterior chamber inflammation or neovascularization (secondary angle closures). PAS may also be associated with anterior segment dysgenesis or other forms of secondary angle closure such as iridocorneal endothelial (ICE) syndrome.

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

Apposition of the iris against the trabecular meshwork as a result of pupil block or a posterior pushing mechanism without any inflammation can result in continuous peripheral anterior synechiae. These continuous peripheral anterior synechiae lead to “zippering” of the angle. Primary angle-closure glaucoma and the various posterior pushing mechanisms are examples of this process.

In the presence of inflammation or cellular proliferation, a membrane forms between the iris and the trabecular meshwork, creating the peripheral anterior synechiae. This membrane contracts, resulting in angle-closure glaucoma by an anterior pulling mechanism. Examples of this process include the fibrovascular membrane formed in neovascular glaucoma, proliferating abnormal endothelial cells in the iridocorneal endothelial (ICE) syndromes, epithelialization of the angle due to epithelial ingrowth, or inflammatory trabecular and keratic precipitates in contact with an inflamed iris. These processes can be accentuated by iris swelling and protein transudation and exudation.

United States

Peripheral anterior synechiae occurs infrequently.

International

Peripheral anterior synechiae occurs infrequently.

The morbidity of peripheral anterior synechiae lies in its ability to occlude the angle and result in a pathological increase in intraocular pressure.

Asian persons have the highest propensity for primary angle-closure glaucoma and, thus, peripheral anterior synechiae formation. [1] This condition is not as common in blacks. Whites are least likely to develop primary angle-closure glaucoma.

Females have shallower anterior chambers; therefore, they may have a greater disposition to forming peripheral anterior synechiae.

The risk of peripheral anterior synechiae formation increases with age because of a reduction in anterior chamber depth. This is due to a combination of cataract formation, leading to an increase in the thickness of the lens, and laxity of the zonules, resulting in the forward displacement of the lens.

Liang YB, Wang NL, Rong SS, Thomas R. Initial Treatment for Primary Angle-Closure Glaucoma in China. J Glaucoma. 2014 Apr 29. [Medline].

Schwartz AL, Whitten ME, Bleiman B. Argon laser trabecular surgery in uncontrolled phakic open angle glaucoma. Ophthalmology. 1981 Mar. 88(3):203-12. [Medline].

Fukuda R, Usui T, Tomidokoro A, Mishima K, Matagi N, Miyai T, et al. Noninvasive observations of peripheral angle in eyes after penetrating keratoplasty using anterior segment fourier-domain optical coherence tomography. Cornea. 2012 Mar. 31(3):259-63. [Medline].

Lin Z, Liang Y, Wang N, Li S, Mou D, Fan S, et al. Peripheral anterior synechia reduce extent of angle widening after laser peripheral iridotomy in eyes with primary angle closure. J Glaucoma. 2013 Jun-Jul. 22(5):374-9. [Medline].

Harasymowycz PJ, Papamatheakis DG, Ahmed I, Assalian A, Lesk M, Al-Zafiri Y, et al. Phacoemulsification and goniosynechialysis in the management of unresponsive primary angle closure. J Glaucoma. 2005 Jun. 14(3):186-9. [Medline].

Teekhasaenee C, Ritch R. Combined phacoemulsification and goniosynechialysis for uncontrolled chronic angle-closure glaucoma after acute angle-closure glaucoma. Ophthalmology. 1999 Apr. 106(4):669-74; discussion 674-5. [Medline].

Takanashi T, Masuda H, Tanito M, Nonoyama S, Katsube T, Ohira A. Scleral indentation optimizes visualization of anterior chamber angle during goniosynechialysis. J Glaucoma. 2005 Aug. 14(4):293-8. [Medline].

Campbell DG, Vela A. Modern goniosynechialysis for the treatment of synechial angle-closure glaucoma. Ophthalmology. 1984 Sep. 91(9):1052-60. [Medline].

Aung T, Tow SL, Yap EY, Chan SP, Seah SK. Trabeculectomy for acute primary angle closure. Ophthalmology. 2000 Jul. 107(7):1298-302. [Medline].

Albert DM, Jakobiec FA. Principles and Practice of Ophthalmology. 2nd ed. Philadelphia: WB Saunders Co; 2000.

Epstein DL, Allingham RR, Schuman JS. Chandler and Grant’s Glaucoma. 4th ed. Baltimore: Lippincott Williams & Wilkins; 1997.

Newell FW. Ophthalmology, Principles and Concepts. 7th ed. St. Louis: CV Mosby; 1991.

Rouhiainen HJ, Terasvirta ME, Tuovinen EJ. Peripheral anterior synechiae formation after trabeculoplasty. Arch Ophthalmol. 1988 Feb. 106(2):189-91. [Medline].

Roy FH. Ocular Differential Diagnosis. 6th ed. Baltimore: Lippincott Williams & Wilkins; 1997.

Description of PAS

Associations

Possible Conditions

Broad bands

 

PAS to all levels but not to cornea No bridging usually present

Angle-closure glaucoma

 

PAS to all levels, sometimes to cornea

Bridging may be present

Posterior pushing mechanism, postoperatively shallow AC, or from iris bombé

 

PAS with new vessels, multiple sites

Neovascularization

Scattered, irregular

 

PAS tent and form columns up to, but not on, the cornea

Iridocyclitis with keratic and trabecular precipitates

 

Small PAS to scleral spur

Post-argon laser trabeculoplasty (ALT)

Iris Pulled Forward

Iris Pushed Forward

Neovascular membrane ICE membrane Posterior polymorphous dystrophy Epithelial/fibrous ingrowth

Uveitis

Pupil block

Trauma

Inflammatory syndromes

Infectious

Lens related

Primary angle-closure glaucoma

Posterior synechiae resulting in iris bombé

Pseudophakic or aphakic pupil block

Iridoschisis

Flat anterior chamber

Plateau iris

Posterior pushing

Postsurgical

Trauma

Choroidal effusion

-Posterior uveitis

-CRVO

-Nanophthalmos

-Post-pan retinal photocoagulation (PRP) or cryotherapy

Suprachoroidal hemorrhage

Ciliary block (malignant) glaucoma (aqueous misdirection)

Posterior segment tumors

-Retinoblastoma

-Choroidal melanoma or metastasis

Iris cyst or tumor

Ciliary body cyst, tumor, or effusion

Contracting retrolental tissue

-Retinopathy of prematurity

-Persistent hyperplastic primary vitreous (PHPV)

Postscleral bucking surgery

Anterior lens subluxation (ectopia lentis)

Lens intumescence (phacomorphic)

Neurofibromatosis

Argon laser trabeculoplasty

 

Andrew J Tatham, MBChB, FRCOphth, FRCSEd, FEBO Consultant Ophthalmic Surgeon, Princess Alexandra Eye Pavilion; Honorary Senior Clinical Lecturer, University of Edinburgh; NHS Scotland Career Research Fellow

Andrew J Tatham, MBChB, FRCOphth, FRCSEd, FEBO is a member of the following medical societies: American Glaucoma Society, Association for Research in Vision and Ophthalmology, Royal College of Ophthalmologists, Royal College of Surgeons of Edinburgh, UK and Eire Glaucoma Society

Disclosure: Serve(d) as a director, officer, partner, employee, advisor, consultant or trustee for: Allergan; Novartis <br/>Serve(d) as a speaker or a member of a speakers bureau for: Allergan; Heidelberg Engineering; Alcon; Novartis .

Simon K Law, MD, PharmD Clinical Professor of Health Sciences, Department of Ophthalmology, Jules Stein Eye Institute, University of California, Los Angeles, David Geffen School of Medicine

Simon K Law, MD, PharmD is a member of the following medical societies: American Academy of Ophthalmology, Association for Research in Vision and Ophthalmology, American Glaucoma Society

Disclosure: Nothing to disclose.

J James Rowsey, MD Former Director of Corneal Services, St Luke’s Cataract and Laser Institute

J James Rowsey, MD is a member of the following medical societies: American Academy of Ophthalmology, American Association for the Advancement of Science, American Medical Association, Association for Research in Vision and Ophthalmology, Florida Medical Association, Sigma Xi, Southern Medical Association, Pan-American Association of Ophthalmology

Disclosure: Nothing to disclose.

Hampton Roy, Sr, MD Associate Clinical Professor, Department of Ophthalmology, University of Arkansas for Medical Sciences

Hampton Roy, Sr, MD is a member of the following medical societies: American Academy of Ophthalmology, American College of Surgeons, Pan-American Association of Ophthalmology

Disclosure: Nothing to disclose.

Bradford Shingleton, MD Assistant Clinical Professor of Ophthalmology, Harvard Medical School; Consulting Staff, Department of Ophthalmology, Massachusetts Eye and Ear Infirmary

Bradford Shingleton, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Ophthalmology

Disclosure: Nothing to disclose.

Iqbal Ike K Ahmed, MD, FRCSC Clinical Assistant Professor, Department of Ophthalmology, University of Utah

Iqbal Ike K Ahmed, MD, FRCSC is a member of the following medical societies: American Academy of Ophthalmology, American Society of Cataract and Refractive Surgery, Canadian Ophthalmological Society, Ontario Medical Association

Disclosure: Nothing to disclose.

Baseer U Khan, MD 

Baseer U Khan, MD is a member of the following medical societies: Canadian Ophthalmological Society

Disclosure: Nothing to disclose.

Khalid Hasanee, MD Glaucoma and Anterior Segment Fellow, Department of Ophthalmology, University of Toronto

Khalid Hasanee, MD is a member of the following medical societies: Canadian Medical Association, Canadian Ophthalmological Society, Ontario Medical Association

Disclosure: Nothing to disclose.

Peripheral Anterior Synechia

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