eMedicine Specialties > Ophthalmology > Pupil

Pupillary Block, Aphakic

Author: Deborah R Eezzuduemhoi, MD, Assistant Professor, Department of Ophthalmology and Visual Sciences, Texas Tech University, Health Sciences Center School of Medicine
Coauthor(s): Deborah Wilson, MD, Director of Glaucoma Service, Assistant Professor, Department of Ophthalmology, Georgetown University Medical Center
Contributor Information and Disclosures

Updated: Jul 23, 2008

Introduction

Background

Aphakia, the absence of the crystalline lens, may occur as a result of trauma, lens subluxation or dislocation, or surgical management of a visually significant cataract. Pupillary block is a complication of cataract surgery with or without lens implantation. Pupillary block in aphakia was a significant complication following round-pupil cataract extraction (without sector iridectomy). This is also possible if an iridectomy was performed but was small and placed in the extreme periphery.

Pathophysiology

Pupillary block is the most common mechanism of angle closure after cataract extraction. This mechanism can be divided into 2 types, namely, anterior pupillary block and posterior pupillary block. A firm apposition between the pupillary margin and other surfaces anterior or posterior to the iris may lead to a pupillary block. The pupillary aperture may be obstructed by the anterior hyaloid surface, the intraocular lens, or the posterior capsule. A postoperative inflammation following an intracapsular cataract extraction may cause complete posterior synechiae between the iris and the intact anterior hyaloid membrane. A shallow anterior chamber favors formation of these adhesions. Adhesions may occur just between the pupillary margin and the anterior hyaloid surface. Such an occlusion is characterized as anterior pupillary block. The aqueous accumulates between the vitreous and the iris causing the peripheral iris to balloon forward.

A distinct mechanism is seen following extracapsular cataract extraction. A greater amount of postoperative inflammation, due to sensitivity to lenticular cortical material, leads to iridocapsular adhesions. This is seen more frequently after congenital cataract surgery. The aqueous humor accumulates between the iris-capsule diaphragm and the anterior hyaloid face, an area known as the canal of Petit. The pressure from the aqueous trapped in the posterior chamber displaces the iris forward. This is posterior pupillary block. The block impedes the forward movement of the aqueous to the anterior chamber leading to iris bombé, obstruction of the angle, and possible formation of peripheral anterior synechiae.

The absence of an iridectomy facilitates the development of pupillary block. Occasionally, this may also occur in eyes with a visible iridectomy if the iridectomy becomes occluded by iridocapsular adhesions.

A similar mechanism of pupillary block is seen with phacomorphic glaucoma and is referred to as anterior aqueous misdirection perilenticular. The aqueous humor accumulates around and behind the crystalline lens leading to lens-iris contact and the obstruction of anterior aqueous movement.

See related CME at Highlights of the American Glaucoma Society 2008 Annual Meeting.

Frequency

United States

While no data exist, pupillary block was common during the era of intracapsular cataract extraction. Many cases are asymptomatic and are only recognized during routine examination. The time of presentation is variable. Pupillary block may present in the immediate postoperative period but has been described from weeks to even years after surgery.

Congenital cataracts should be removed early in order to achieve the best possible visual outcome. Pupillary block with secondary angle-closure glaucoma within a few months following surgery has been linked to the cataract extraction. It seems that there is a need to reevaluate the appropriate time for cataract surgery in infants.

According to one study, 11% cases of silicone oil injection in aphakic patients resulted in angle closure and high intraocular pressure (IOP) due to obstruction and tamponade of the trabecular meshwork.

Mortality/Morbidity

In aphakia, pupillary block impedes the forward movement of the aqueous through the pupillary aperture. With continuous production of aqueous the peripheral iris bows forward (iris bombé). This condition then leads to obstruction of the iridocorneal angle; formation of peripheral anterior synechiae (PAS), further aggravating the passage of aqueous toward the angle; rise in the IOP; and glaucomatous disc damage and associated visual field defects.

Age

In this era of intraocular lenses, pupillary block is seen not only in older individuals who are rendered aphakic but also in infants who undergo surgery for congenital cataracts.

Clinical

History

• Painful red eye
• Blurry vision or acute decrease in vision
• Headache
• Nausea
• Vomiting

Physical

Slit lamp examination

• Cornea: Epithelial and stromal edema may be seen.
• Anterior chamber
  • Overall shallowing of the anterior chamber with a normal or elevated IOP is the usual presenting sign of pupillary block. However, iris bombé is the classic presentation.
  • The disparity between the central and the peripheral anterior chamber depth, with a deeper central depth is a result of posterior synechiae.
  • The presence of inflammatory debris or blood may cause an unevenness in the anterior chamber depth.
• Pupil
  • Seclusio pupillae or posterior synechiae may be seen.
  • A mushroomlike plug of vitreous protruding through the pupil may be seen.
• Gonioscopy
  • Forward bowing and convexity of the iris periphery is seen on gonioscopic evaluation.
  • Shallowing and then flattening of the anterior chamber results in the loss of view of the iridocorneal angle structures.
  • Initially, an appositional closure can be present, which may lead to permanent angle closure at a later stage.
  • PAS are evidence of chronicity.

Causes

A number of conditions predispose to the development of aphakic pupillary block, to include the following:

• Wound leakage can result in shallowing of the anterior chamber and can be associated with hypotony. This may be exaggerated by the rotation of the ciliary body and displacement of the vitreous, which can promote blockage of the pupillary aperture.
• Complete adhesion along the pupillary margin (seclusio pupillae) may result from any cause of severe postoperative inflammation (eg, retained lens material).
• Inadequate postoperative mydriasis
• Air bubble
  • Injection of air into the anterior chamber of a hypotonic eye following cataract extraction has been shown to be potentially hazardous.
  • Preoperatively, some eyes are rendered hypotonus by osmotic agents (eg, mannitol, glycerol), and these eyes may accept a considerable amount of air at the end of the surgery.
  • With resumption of normal fluid volume, the air will be compressed and forced into the posterior chamber, causing the iris to move forward leading to pupillary block. This condition is usually self-limited with resorption of the air bubble.
• Gas bubble
  • In an aphakic eye, a gas bubble anterior or posterior to the iris may interfere temporarily with the passage of aqueous humor across the pupil and predispose to pupillary block.
  • Pupillary block arises if the volume is of substantial amount as in the case of expanding gases (eg, sulfur hexafluoride [SF₆], octafluoropropane [C₃ F₈]) used in retinal reattachment surgery. Following expansion, these gases may occupy the entire vitreous cavity and displace the iris forward, subsequently blocking the pupil.
  • Kumar et al described a case of aphakic pupillary block following the use of perfluoropropane (or octafluoropropane) (C₃ F₈) at a nonexpansile concentration of 14%.¹
• Vitreous plugging
  • Vitreous gel has been recognized as an etiology of pupillary block by many authors. After intracapsular cataract extraction without sector iridectomy, the intact anterior hyaloid molds itself into the pupillary aperture leading to a secondary angle closure.
  • In some cases, even in the presence of small peripheral iridectomy, the vitreous can plug the openings and lead to angle closure. Shaffer observed that posterior vitreous detachment predisposed to such pupillary block.²
  • Pupillary block by the vitreous has been described following surgical discission of posterior capsule as well as Nd:YAG laser posterior capsulotomy.
  • Posner has described 3 stages of pupillary block by the vitreous, as follows:³
    • An early stage characterized by relative block due to decreased permeability of the hyaloid face.
    • A moderate stage with adhesions between the vitreous and sphincter pupillae referred to as sphincteric pupillary block.
    • The irido-hyloidal stage with extensive adhesions between the anterior hyaloid face and the entire posterior iris surface.
• Silicone oil
  • Pupillary block has been described in aphakic eyes after retinal reattachment surgery with silicone oil injection, both in the immediate and long-term postoperative periods.
  • Pars plana vitrectomy with silicone oil injection is being performed with increasing frequency in proliferative vitreoretinopathy.
    • Because of the cohesive forces, the silicone oil takes a smooth spherical form within the aqueous in the vitrectomized posterior segment.
    • Since silicone oil is lighter than aqueous humor, it settles superiorly behind the iris. Thus, a superiorly placed peripheral iridectomy may become blocked.
    • In addition, if the silicone oil fills the vitreous cavity as the aqueous is being produced, it may force the silicone oil through the pupil.
    • If the silicone oil completely fills the vitreous cavity, the pupillary space, and the entire anterior chamber, the IOP may rise further as aqueous humor may have no access to the trabecular meshwork.

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