Continuing Education Activity

Urrets-Zavalia syndrome (UZS) is a rare and severe complication that can arise following ophthalmic surgeries, particularly penetrating keratoplasty. The prevalence of this condition ranges from 2.2% to 17.7%, although the exact mechanisms and risk factors remain somewhat speculative. Potential contributing factors include elevated intraocular pressure, use of mydriatic agents, keratoconus, and retention of viscoelastic material. UZS is characterized by a fixed and dilated pupil, typically presenting 1 to 2 weeks postoperatively, and is believed to result from iris ischemia and subsequent dysfunction of the pupillary sphincter muscles. Clinicians should be aware that UZS can lead to acute angle-closure glaucoma—a vision-threatening condition.

Currently, an approved treatment for UZS does not exist, but management focuses on controlling intraocular pressure and inflammation, with various surgical and nonsurgical interventions to address complications such as photophobia and glaucoma. This article provides comprehensive insights into the etiology, pathophysiology, differential diagnosis, management, complications, and prognosis of UZS. This activity helps clinicians recognize the clinical presentation and diagnostic features of UZS, including the importance of a detailed patient history, medication review, and appropriate use of diagnostic tools such as slit lamp examination, gonioscopy, and ultrasound biomicroscopy. This activity will explore several preventative measures and their efficacy, providing clinicians with strategies to minimize the risk of UZS in susceptible patients.

Objectives:

• Identify the clinical presentation and diagnostic features of Urrets-Zavalia syndrome following ophthalmic surgeries.
• Implement appropriate diagnostic tools such as slit lamp examination, gonioscopy, and ultrasound biomicroscopy to confirm Urrets-Zavalia syndrome.
• Select optimal management strategies to control intraocular pressure and inflammation associated with Urrets-Zavalia syndrome.
• Collaborate with multidisciplinary healthcare teams, including optometrists and ophthalmologists, to optimize care for patients with Urrets-Zavalia syndrome.

Introduction

In 1963, Alberto Urrets-Zavalia, an Argentinian ophthalmologist, observed 6 patients with fixed mydriatic pupil, iris atrophy, posterior synechiae, and secondary glaucoma after undergoing penetrating keratoplasty for keratoconus.[1] All cases except 1 received topical atropine in this series, and the author suggested that atropine was crucial in causing this clinical condition.[1] 

Urrets-Zavalia Syndrome (UZS), also known as Castroviejo syndrome, is a rare and severe complication characterized by a fixed and dilated pupil following various ophthalmic surgeries, sometimes associated with keratoconus or the use of postoperative mydriatic agents.[2][3] Castroviejo was the first to mention this clinical condition, while Urrets-Zavalia provided a detailed characterization of the condition.[2][3][4]

Although penetrating keratoplasty is the most common implicated procedure for this syndrome,[5] UZS has been reported following various ophthalmic surgical procedures, including deep anterior lamellar keratoplasty (DALK),[6] Descemet stripping automated endothelial keratoplasty (DSAEK),[7] cataract surgery,[8] and various glaucoma surgeries.[9][10][11] Patients usually present with an atonic pupil that does not constrict to light or accommodation.[12] The onset of symptoms varies but commonly occurs 1 to 2 weeks after penetrating keratoplasty.[13]

The development of UZS is widely attributed to iris ischemia,[14] which results in subsequent dysfunction of the pupillary sphincter muscles.[15] Although various preventive measures have been attempted,[16][17] an approved treatment for UZS is not currently available. 

Etiology

Although the etiology of UZS is not well understood, several potential risk factors mentioned below are believed to be involved in its development:

• Increased intraoperative or postoperative intraocular pressure (IOP) [2]
• Use of mydriatic agents during or after surgical intervention [18]
• Presence of keratoconus [2][19]
• Retention of viscoelastic material in the anterior chamber angle [20]
• Air or gas injection into the anterior chamber [21][22][23]
• Inflammation in the anterior chamber [5]

These risk factors have been debated due to conflicting data from limited reports and studies on UZS. UZS has been reported following various ophthalmic interventions, including:

• Penetrating keratoplasty for indications such as keratoconus, macular corneal dystrophy, granular corneal dystrophy, Fuchs endothelial corneal dystrophy, chemical injury, fungal corneal ulcer, leucoma, and herpetic keratitis.[5][24][25]

• DALK for indications, including keratoconus, granular corneal dystrophy, and macular corneal dystrophy, may be associated with UZS.[26][27] Specifically, DALK procedures involving Descemet membrane perforation and intracameral air usage may predispose to UZS.[23]

• Descemet stripping endothelial keratoplasty (DSEK) or DSAEK is performed for bullous keratopathy and corneal edema resulting from endothelial dysfunction.[27][28] High IOP and and a complex postoperative course, such as graft dislocation requiring rebubbling or re-DSAEK, may predispose to a dilated irregular pupil resembling Urrets-Zavalia syndrome.[28]

• Descemet membrane endothelial keratoplasty (DMEK) is performed for Fuchs endothelial corneal dystrophy.[29]

• Intracameral gas (C3F8) injection is used for acute corneal hydrops.[30]

• Cataract surgery (including small incision cataract surgery, phacoemulsification, and conventional extracapsular cataract extraction) with postoperative toxic anterior segment syndrome (TASS) has been associated with the development of Urrets-Zavalia syndrome.[31][32] In a large study, the Ringer lactate solution was implicated in causing TASS, subsequently leading to Urrets-Zavalia syndrome.[32] Some authors suggest that toxic anterior segment syndrome and Urrets-Zavalia syndrome may represent a spectrum of the same entity.[31] Urrets-Zavalia syndrome has also been reported 3 weeks after femtosecond laser-assisted cataract surgery, which was associated with anterior segment inflammation appearing 2 weeks post-surgery.[33]

• Scleral-fixated intraocular lens.[34]

• Trabeculectomy and combined trabeculotomy and trabeculectomy may be associated with Urrets-Zavalia syndrome.[11][35] These patients may experience a complicated postoperative course, including hypotony requiring multiple surgeries and spikes in high IOP.[11]

• Goniotomy.[9]

• Minimally invasive glaucoma surgery.

• Glaucoma drainage device.[36]

• Argon laser peripheral iridoplasty.[10][11]

• Implantable collamer lens placement.[37][38]

• Iatrogenic dilation of the pupil in patients with pigment dispersion syndrome.[39] 

• Intravenous cidofovir injection with ocular hypotony.[40]

Epidemiology

The incidence of Urrets-Zavalia syndrome is rare and highly variable, with reported frequencies ranging from 0% to 17.7% after penetrating keratoplasty.[1][5][41][42] This variability may be due to differences in diagnostic criteria, underdiagnosis, and a transient, mild form in which the pupil size normalizes over time.[19] The current literature does not provide an accurate overall incidence rate. Differences in frequency among sexes and age groups are not entirely known. Urrets-Zavalia syndrome typically occurs unilaterally despite bilateral surgery and affects males and females equally.[5][35][43] Bilateral cases of UZS have been reported in macular corneal dystrophy patients undergoing penetrating keratoplasty, possibly suggesting an abnormal iris or sphincter pupillae in both eyes.[24]

Pathophysiology

The pathophysiology of Urrets-Zavalia syndrome is not well understood but is likely multifactorial. Iris ischemia is considered a primary mechanism behind the pupillary sphincter dysfunction observed in UZS patients.[44] The severity of ischemia and resulting atrophy determines the extent of dilation and the potential for the pupil to return to normal size.[3][14] Additional possible mechanisms include intraoperative iatrogenic trauma to the iris, ciliary muscles, or ciliary ganglion, as well as toxic or idiosyncratic reactions to various agents, including anesthetics.[45]

High intraoperative or postoperative IOP is thought to cause occlusion of the iris root vessels, leading to ischemia and subsequent iris atrophy.[1] In 1995, Tuft demonstrated through anterior-segment fluorescein angiography that keratoconus patients with high postoperative IOP after penetrating keratoplasty exhibited delayed filling of the iris vessels with late-stage leakage, indicative of iris ischemia.[44] Elevated IOP within the first 24 hours after surgery may be a strong predictive factor for the development of UZS.[19] However, UZS cases have also been reported with normal IOP.[33]

A proposed mechanism for why keratoconus patients may be at higher risk for Urrets-Zavalia syndrome after penetrating keratoplasty is that the low rigidity of keratoconic eyes may obstruct the peripheral iris vessels that insert into the sclera during the procedure.[44] Another proposed theory is that patients with keratoconus may have intrinsic deficiencies in their irises and pupillary sphincter muscles, leading to a higher susceptibility to postoperative mydriasis.[41] Some authors have noted prompt and sustained pupillary dilation with mydriatic drop use in keratoconus patients, even if they do not undergo penetrating keratoplasty.[14] Other hypotheses include a sudden increase in sympathetic effect on the pupil, a neurochemical defect of the sphincter pupillae or dilator pupillae, a lower amplitude of accommodation response suggesting abnormality of the iris and ciliary body, and iris hypoplasia.[4] However, However, a large study noted that atropine, high IOP, and keratoconus are not consistently seen in all cases of UZS.[24] Many authors have suggested that keratoconus may not be a predisposing factor for UZS.[42][46]

Historically, mydriatic agents such as atropine were thought to have a role in the pathogenesis of UZS.[18] Atropine may cause permanent or prolonged mydriasis, or "abnormally great mydriasis," in Down syndrome due to hyperreactivity to atropine.[47] However, contradicting literature exists.[48][49] Patients with pigment dispersion syndrome may also develop fixed dilated pupils after iatrogenic mydriasis.[39] Drugs acting on both parasympathetic (including atropine and homatropine) and sympathetic (phenylephrine) pathways may be associated with UZS.[31] The proposed mechanism is that the mydriasis induced by the instillation of these agents may increase contact between the iris and the cornea, causing iris atrophy and prolonged mydriasis.[50] Urrets-Zavalia syndrome may occur in the eyes without contact between the peripheral iris and the host cornea.[50] A study showed that postoperative mydriasis was detected equally in keratoconus patients who received or did not receive mydriatic agents during or after penetrating keratoplasty.[41] In addition, Urrets-Zavalia syndrome may occur in patients without a history of mydriatic use.[35]

Ophthalmic viscosurgical devices or viscoelastic materials may be toxic to the pupillary sphincter or iris vasculature, raising the notion that UZS may also be a sequelae of TASS.[31] This hypothesis has been considered in cases of UZS following cataract surgery, where viscoelastic material was found in the anterior chamber angle.[20] In addition, it has also been speculated that viscoelastic material retention may lead to an IOP spike and subsequent damage to the iris vasculature.[51]

In addition to penetrating keratoplasty, other ophthalmic surgeries have been associated with the development of Urrets-Zavalia syndrome, and their potential mechanisms have been described. Air bubble formation in the anterior chamber with subsequent posterior displacement of the iris is thought to be the reason for Urrets-Zavalia syndrome after DALK and DSAEK.[22][52] Various glaucoma surgeries such as argon laser peripheral iridoplasty (ALPI), trabeculectomy (TREC), and goniotomy may lead to permanent mydriasis, possibly due to injury of the parasympathetic radial nerve fibers to the pupillary sphincter muscle.[9][10][11]

Histopathology

A biopsy from a keratoconus patient who developed Urrets-Zavalia syndrome after penetrating keratoplasty showed stromal fibrosis and dilated iris vessels (vascular congestion).[53] The Schlemm canal was patent, and the trabecular meshwork appeared normal in the specimen taken after a trabeculectomy. Lymphoid cells were present around the Schlemm canal. The posterior pigmentary epithelium was normal, and no neovascularization with thin walls was observed in this report.[53]

History and Physical

Patients with Urrets-Zavalia syndrome typically present with an atonic pupil that does not react to light, accommodation, or pilocarpine and may experience glare, halos, and photophobia.[3] The onset is usually within the first 1 to 2 weeks after penetrating keratoplasty.[24] However, Urrets-Zavalia syndrome has been reported up to 5 months postoperatively.[19] IOP may be elevated, and there may be evidence of glaucomatous optic nerve head damage.[54]

On slit lamp examination, diffuse atrophy of the anterior and posterior layers of the iris with posterior synechiae and glaukomflecken may be observed in the complete form of Urrets-Zavalia syndrome.[1][55] The permanent mydriasis observed in the complete form of Urrets-Zavalia syndrome caused by diffuse iris atrophy may lead to adhesions and occlusions of the anterior chamber angle, resulting in secondary acute angle-closure glaucoma.[56]

The incomplete and transient forms of Urrets-Zavalia syndrome may exhibit anterior layer atrophy of the iris with pigmentary granules on the corneal endothelium and anterior lens capsule.[1] Sequelae of TASS, including corneal decompensation, posterior synechia, pigment deposition on the anterior surface of the lens, and corneal endothelium, may also be observed. Features suggestive of iris ischemia or strangulation, including transillumination defects, may be present. In the complete form of Urrets-Zavalia syndrome, the pupil fails to constrict even after topical instillation of pilocarpine 2% or 4% eye drops.[45]

Evaluation

A thorough medical and surgical history should be obtained from the patient, including a review of medications to identify any use of mydriatic agents. Visual acuity, postoperative IOP, and pupillary examination should be adequately performed.

A feared complication of Urrets-Zavalia syndrome, as mentioned before, is secondary acute-angle closure glaucoma.[1] After evaluation and diagnosis of Urrets-Zavalia syndrome via slit lamp examination, a gonioscopy should be performed to assess the presence and degree of adhesions or peripheral anterior synechiae in the anterior chamber angle.[56] Ultrasound biomicroscopy (UBM) can be considered in cases of unsuccessful gonioscopy. Ancillary testing such as corneal tomography, optical coherence tomography (corneal thickness, anterior segment or angle of the anterior chamber, posterior segment, and optic nerve), and anterior segment fluorescein angiography can be considered but not required for diagnosis.

Anterior segment indocyanine green angiogram shows delayed and reduced filling of the iris vessels compared to control, suggesting iris ischemia's crucial role in the causation of Urrets-Zavalia syndrome.[19]

Treatment / Management

Currently, no definitive treatment has been provided for Urrets-Zavalia syndrome at this time. Current literature regarding medical therapy has suggested the use of dapiprazole [57] and guanethidine drops [13] due to their sympatholytic mechanisms and ability to induce miosis. A study demonstrated successful treatment of iris sympathetic spasms and miosis with guanethidine 5% eye drops every 4 hours for 24 hours, followed by pilocarpine 2% drops the next day.[58] However, further research is needed to evaluate the safety and effectiveness of these medications. Control of intraocular inflammation and management of IOP remain crucial aspects of treatment. 

Surgical interventions are reserved for cases where there is iridocorneal contact and a shallow anterior chamber. A cyclodialysis spatula can be used to disrupt adhesions in the anterior chamber angle and restore the anterior chamber.[50] Pupilloplasty may be necessary for patients experiencing severe photophobia that cannot be managed with sunglasses and other conservative measures. Various techniques of pupilloplasty have been reported, including single-pass and 4-throw pupilloplasty.[59] Additional options for controlling photophobia due to dilated pupils include corneal tattoos, femtosecond-assisted keratopigmentation, contact lenses, and diaphragm intraocular lenses.[60] In cases where IOP needs to be controlled, glaucoma surgery may be required. Some cases may also necessitate anterior segment reconstruction.

Several preventative measures have been utilized preoperatively thus far based on current theories regarding risk factors. Preoperative administration of intravenous mannitol 20% has been used to reduce vitreous humor volume and mitigate iris strangulation caused by intraoperative spikes in IOP.[16] YAG laser iridotomy may also be performed a day before penetrating keratoplasty to manage elevated IOP.[17] Intraoperatively, the surgeon must exercise caution to prevent surgical trauma to the iris and ensure adequate anterior chamber depth. If viscoelastic material is used, it should be thoroughly removed from the anterior chamber to prevent potential toxic reactions. Some surgeons advocate for peripheral surgical iridectomy during penetrating keratoplasty to prevent pupillary block and iris strangulation,[61] although the efficacy of iridectomy in preventing Urrets-Zavalia syndrome is debated among authors.[4] 

Urrets-Zavalia syndrome may be associated with intracameral air or gas, particularly in procedures such as DSAEK and DALK with Descemet membrane perforation, highlighting the need for cautious use of these agents and consideration of intravenous mannitol.[23] The role of preoperative antiglaucoma medications in preventing UZS remains uncertain. Controversy surrounds the use of postoperative mydriatics, which some authors speculate may contribute to the onset of Urrets-Zavalia syndrome. Recommendations include avoiding potent mydriatics such as atropine or homatropine and considering the use of short-acting agents such as phenylephrine on alternate days.[4]

Differential Diagnosis

A thorough differential diagnosis should be undertaken upon observing a patient with a dilated and fixed pupil following ophthalmic surgery. The following conditions should be considered when encountering a patient with a unilaterally atonic pupil:

• Acute angle-closure glaucoma
• Anterior uveitis
• Posterior synechiae
• Pupillary block
• Neurogenic syphilis
• Iatrogenic iris trauma
• Traumatic mydriasis
• Adie pupil
• Pharmacologic mydriasis
• Third nerve palsy

Prognosis

Approximately 30% to 70% of patients with Urrets-Zavalia syndrome will regain some form of pupil reactivity within 18 weeks after onset.[62] Jastaneiah et al reported that only 4.8% of UZS patients regain a normal pupil size, focusing on the complete form of Urrets-Zavalia syndrome.[24] Potential predictors for recovery of pupillary light reflex and normal pupillary size include prompt control of postoperative IOP rise, light reaction in the dilated pupil, and pupillary constriction with topical pilocarpine 2% eye drops.[37] Around 30% of cases never recover pupillary movement.[45] Permanently fixed dilated pupils may require pupilloplasty or other interventions if the patient experiences photophobia.

Complications

The major complication of Urrets-Zavalia syndrome is secondary acute angle-closure glaucoma, which occurs due to the formation of iridocorneal adhesions and subsequent collapse of the anterior chamber angle.[1] Prompt diagnosis is essential to preserve the patient’s optic nerve and vision. Management includes the use of IOP-lowering medications and subsequent surgical interventions aimed at adhesion removal and reformation of the anterior chamber.[50]

Deterrence and Patient Education

Patients with Urrets-Zavalia syndrome should be counseled by their healthcare providers about the risks of developing acute angle-closure glaucoma. They should avoid dimly lit environments to prevent further mydriasis and narrowing of the iridocorneal angle. Additionally, patients should be cautioned against using medications such as specific anticholinergic, adrenergic, antidepressant, and sulfa-based agents, which can exacerbate mydriasis and increase the risk of angle-closure glaucoma.[63] 

Patients with Urrets-Zavalia syndrome who have hypermetropia should also receive education about their inherent risk for angle-closure glaucoma. These individuals have an anatomical predisposition to a shallow anterior chamber depth or a more anteriorly located lens, both of which can increase the likelihood of angle-closure glaucoma.[64]

Enhancing Healthcare Team Outcomes

Clinicians should consider Urrets-Zavalia syndrome as a possible complication following penetrating keratoplasty or other ophthalmic surgeries. General practitioners, nurses, and other multidisciplinary healthcare team members should include this diagnosis in their differential for an atonic pupil after eye surgery. They should promptly refer the patient to their optometrist or ophthalmologist. Careful pre- and intraoperative measures should be planned and adopted to minimize the risk of Urrets-Zavalia syndrome. Although rare, Urrets-Zavalia syndrome should not be overlooked in the early postoperative period due to the potential for secondary acute angle-closure glaucoma, which can threaten vision. The implementation of the preventive measures discussed above may reduce the risk and incidence of Urrets-Zavalia syndrome.

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Disclosure: Majid Moshirfar declares no relevant financial relationships with ineligible companies.

Disclosure: Kayvon Moin declares no relevant financial relationships with ineligible companies.

Disclosure: Yasmyne Ronquillo declares no relevant financial relationships with ineligible companies.