Open Veterinary Journal, (2022), Vol. 12(1): 138–147 ISSN: 2226-4485 (Print) Case Report ISSN: 2218-6050 (Online) DOI: 10.5455/OVJ.2022.v12.i1.17 Submitted: 21/10/2021 Accepted: 23/01/2022 Published: 26/02/2022 Urrets-Zavalia syndrome following cataract surgery in dogs: A case series Francisco Cantero1,2 , Marta Leiva1,2* , Laura Gaztelu1,2 , Irene Cerrada1,2 , Rita Vilao Cardoso1,2 , and Teresa Peña 1,2 1 Servei d’Oftalmologia, Fundació Hospital Clínic Veterinari, Universitat Autònoma de Barcelona, Bellaterra, Spain 2 Departament de Medicina i Cirurgia Animals, Facultat de Veterinària, Universitat Autònoma de Barcelona, Bellaterra, Spain Abstract Background: In human medicine, Urrets-Zavalia syndrome (UZS) is a well-recognized but uncommon postoperative complication characterized by a fixed dilated pupil, accompanied by iris atrophy and glaucoma. Although it was originally reported in 1963 after penetrating keratoplasty surgery for keratoconus, it has been associated with various ophthalmic procedures such as cataract surgery. The condition has not been previously published in the veterinary literature. Case Description: Three client-owned diabetic dogs that developed UZS´s triad after cataract surgery are described. Despite uneventful phacoemulsification in the six eyes, five developed moderate-to-severe postoperative ocular hypertension. Although intraocular pressure (IOP) spikes were initially controlled, fixed dilated pupils accompanied by iris atrophy and chronic ocular hypertension were seen in the five affected eyes. Aggressive medical and surgical management maintained vision in three of those eyes. In one eye, uncontrolled IOP led to blindness. Conclusion: This is the first published description of UZS in dogs, occurring after phacoemulsification. Although no exact, demonstrable causative element could be determined, we believe that should be considered a triggering condition for this syndrome, as it directly affects the ocular blood flow autoregulation and intrinsic uveal tissue integrity. Until the contrary is proved, diabetes mellitus might be considered as a risk factor for developing this syndrome after cataract surgery in dogs. Keywords: Iris atrophy, Mydriasis, Ocular hypertension, Phacoemulsification, Postoperative complication. Introduction unknown. The dilated pupils do not seem to respond In 1963, an Argentinian ophthalmologist named to pilocarpine, sympatholytic agents, or to alpha- Alberto Urrets-Zavalia described a fixed and dilated adrenergic blockers. Hence, the treatment in human pupil syndrome, accompanied by iris atrophy and patients is directed toward the symptomatic control of glaucoma, as a complication of penetrating keratoplasty glare, intraocular pressure (IOP), and photophobia with for keratoconus (Urrets-Zavalia, 1963). At that time, concealment of anisocoria with cosmetic contact lenses the author associated the uncommon postoperative (Narang et al., 2017) or corneal micro pigmentation complication with the use of topical mydriatic agents (Reed, 1994; Alio et al., 2012). (atropine). Later on, this syndrome was described in In the veterinary literature, apart from a case report association with other surgical procedures, such as recently presented at the European College of Veterinary different methods of keratoplasty (Maurino et al., Ophthalmologists meeting (Bilotta and Busse, 2021), 2002; Minasian and Ayliffe, 2002; Srinivasan and no descriptions of UZS have been published, so far. Patnaik, 2004; Fournié et al., 2009; Anwar et al., Herein, we describe three cases of UZS in diabetic 2012; Bozkurt et al., 2012; Foroutan et al., 2016), dogs occurring after cataract surgery and discuss the intracameral gas injection for the treatment of corneal etiological mechanisms for this syndrome. hydrops (Aralikatti et al. 2008), trabeculectomy (Jain Case Details et al., 2000), goniotomy (Chelnis et al., 2012; Walton, 2013), intraocular lens implantation (Yuzbasioglu et The medical records of three client-owned dogs that al., 2006; Park et al., 2008; Pérez-Cambrodí et al., developed clinical signs compatible with UZS after 2013; Narang et al. 2017), cataract surgery (Monson bilateral cataract surgery at the Veterinary Teaching et al., 1992), argon laser retinal photocoagulation Hospital of the Autonomous University of Barcelona (Lifshitz and Yassur, 1988), 360-degree peripheral (VTH-UAB) from 2020 to 2021 were retrospectively iridoplasty (Espana et al., 2007), and anterior chamber reviewed. In the short-term postoperative period of foreign body removal (Totuk et al., 2018). The exact uneventful phacoemulsification, the syndrome was mechanism of Urrets-Zavalia syndrome (UZS) is still suspected when an acute, fixed and dilated pupil, *Corresponding Author: Marta Leiva. Servei d’Oftalmologia, Fundació Hospital Clínic Veterinari, Universitat Autònoma de 138 Barcelona, Bellaterra, Spain. Email: marta.leiva@uab.cat http://www.openveterinaryjournal.com F. Cantero et al. Open Veterinary Journal, (2022), Vol. 12(1): 138–147 accompanied with clinical iris atrophy and glaucoma solution, refrigerated Ringer´s solution, 2.2% sodium were detected. hyaluronate viscoelastic (An-bfh 2.2%®, an-vision, Signalment, clinical findings, and preoperative Hennigsdorf, Germany), and intracameral tissue evaluation plasminogen activator (0.25 µg/0.1 ml). In all the eyes, There were two spayed females [a mix breed dog (case and acrylic lens of the appropriate size was inserted 1) and an Ibizan Warren Hound (IWH; case 2)] and a in the capsular bag (MD8®, an-vision, Hennigsdorf, neutered male [Yorkshire Terrier (YT; case 3)], of ages Germany). All surgeries were uneventful, and sodium between 9 and 10 years and 4–15 kg. All the animals hyaluronate was removed using the automated were diagnosed with diabetes mellitus 2–5 months prior irrigation/aspiration system following placement to presentation. Owners reported that the dogs have of the IOL. For all the eyes, 45º mini-flared Kelman gone blind within a very short period after the diagnosis tips were used, and phacoemulsification metrics were of diabetes (1–3 months). Apart from hypothyroidism recorded (Table 3). The corneal incision was closed by in case 2, no other concurrent systemic diseases were 3–4 simple interrupted sutures (Dafilon 9/0®, B Braun, detected, and complete physical examinations at Melsungen, Germany), resulting in a watertight seal. presentation were unremarkable. Recovery from general anesthesia was uneventful. Ocular findings at the first presentation are summarized Immediate and short-term postoperative management in Table 1. In three dogs, initial ophthalmic Immediate postoperative management included examination revealed absent menace response in both buprenorphine (15 µg/kg IV; Buprex®, Indivior Europ eyes (OU) with no other relevant findings in the neuro- Limited, Dublin, Ireland), topical 0.1% nepafenac q4h ophthalmological examination. Schirmer Tear Test 1 (Nevanac 1 mg/ml®, Alcon Healthcare, Barcelona, (MSD Animal Health, Madison, NJ) and tonometric Spain), ciprofloxacin q4h (Oftacilox®, Alcon Healthcare, values (TonoVet®, Icare Finland Oy, Helsinki, Finland) Barcelona, Spain), carbomer gel q4h (Viscotears®, were within normal limits. Biomicroscopic examination Bausch & Lomb, Laval, CA) and tonometry every 2 (Kowa SL17®, Kowa Company Ltd., Tokyo, Japan) hours for the first 24 hours. IOP spikes were treated revealed intumescent cataracts OU, impairing fundus accordingly to the “VTH-UAB protocol for managing examination. Although mild senile iris atrophy was postoperative intraocular pressure spikes in dogs,” bilaterally seen in cases 1 and 2, pupillary light reflexes which includes topical carbonic anhydrase inhibitors, (PLRs) were not affected. Fluorescein test was negative beta-blockers, synthetic prostaglandins, and anterior in all the eyes. chamber decompression (ACD), depending on the IOP Abnormalities of the preoperative complete blood values (Table 4). Five out of the six eyes developed count and serum biochemistry studies for each moderate-to-severe postoperative ocular hypertension dog are summarized in Table 2. In all the eyes, the (POH) (40–75 mmHg), requiring a combination of preoperative gonioscopic evaluation revealed an open topical antiglaucoma drugs with ACD. The number of iridocorneal angle (ICA) with no pectinate ligament ACD needed to return the IOP to normal levels (≤20 dysplasia. In addition, ocular ultrasound examination mmHg) were as follows: case 1 (3 ACD OU), case 2 was unremarkable, with biometric measurements of the (2 ACD OU), and case 3 [1 ACD in the left eye (OS)]. crystalline lens diameter varying between 12.9 and 14.3 Postoperative treatment at discharge consisted of mm, and short-protocol electroretinography revealed topical 0.1% nepafenac q4h, ciprofloxacin q4h, regular retinal activity in all the eyes. carbomer gel q4h, and tropicamide q12h, as well as Preoperative treatment and surgical procedure robenacoxib q24h (1 mg/kg, Onsior®, Elanco, IN). In All the dogs were treated 5–6 hours before surgery addition, a combination of dorzolamide and timolol with flunixin-meglumine (0.5 mg/kg IV; Nixyvet (Cosopt®, Santen Oy, Tampere, Finland) was added OU 50mg/ml®, Divasa-Farmavic, S.A. Group, Barcelona, q6h in cases 1 and 2. Spain), and at anesthesia induction with cefazolin (25 At first recheck, 1 week postoperatively, dogs seemed to mg/kg IV; Cefazolina Normon, Laboratorios Normon cope well with medication; nevertheless, cases 2 and 3 S.A., Madrid, Spain). In addition, topical tropicamide showed signs of unilateral discomfort in the right and left (Colircusí Tropicamida®, Alcon Healthcare, Barcelona, eye, respectively. At the examination, menace response Spain), 1% phenylephrine (Colircusí Fenilefrina®, was present OU in dogs 2 and 3 while diminished in Alcon Healthcare, Barcelona, Spain), 0.1% nepafenac dog one. Five out of the six eyes showed dazzle reflex (Nevanac 1 mg/ml®, Alcon Healthcare, Barcelona, but absent PLRs with unresponsive mydriatic pupils. Spain), and ciprofloxacin (Oftacilox®, Alcon At that time, mydriasis was classified as severe in three Healthcare, Barcelona, Spain), were applied every 30 eyes (case 1 OU and case 3 OS) and moderate in 2 minutes for 2 hours. (case 2 OU) (Fig. 1). IOPs values were as follow: case Cataract surgery consisted of a routine one-handed 1 [55 mmHg right eye (OD); 42 mmHg OS], case 2 (72 divided-and-conquer phacoemulsification procedure mmHg OD; 12 mmHg OS) and case 3 (5 mmHg OD; using a peristaltic pump (Alcon Infinity Vision System®, 57 mmHg OS). Biomicroscopic examination revealed Alcon Healthcare, Barcelona, Spain). Intracameral different degrees of bulbar conjunctival congestion fluids used along the surgery included: balanced salt and diffuse corneal edema; all the eyes showed mild 139 140 F. Cantero et al. Table 1. Ocular findings of dogs affected by UZS after cataract surgery. Findings at first presentation and last recheck are shown. First ophthalmic examination Last ophthalmic examination Vision IOP Inflammation Vision IOP Inflammation IOL Menace Dazzle DPLR (mmHg) =(Aqueous flare) Menace Dazzle DPLR (mmHg) (Aqueous flare) Position http://www.openveterinaryjournal.com - OD - + + 17 - - NC (severe 7 Very mild N mydriasis) Case 1 - OS - + + 18 - + + (severe 7 Very mild N mydriasis) - OD - + + 10 - - - (moderate 16 Very mild N mydriasis) Case 2 - OS - + + 9 - + + (moderate 6 - N mydriasis) OD - + + 13 - + + + 7 Mild N Case 3 - OS - + + 15 - + + (moderate 22 Very mild N mydriasis) (NC): Non-conclusive; (N): Normal. Open Veterinary Journal, (2022), Vol. 12(1): 138–147 http://www.openveterinaryjournal.com F. Cantero et al. Open Veterinary Journal, (2022), Vol. 12(1): 138–147 Table 2. Abnormalities of the preoperative complete blood count and serum biochemistry studies for three dogs affected by UZS. Complete blood count Biochemistry Parameter Result Reference range Parameter Result Reference range Glucose 528 70–143 mg/dl Erythrocytes 9.12 5.65–8.87 M/µl Sodium 142 144–160 mmol/l RDW 22.7 13.6–21.7 % Case 1 Chloride 106 109–122 mmol/l Reticulocytes 156.9 10.0–110.0 K/µl IWH Albumin 4.2 2.2–3.9 g/dl Lymphocytes 0.77 1.05–5.10 K/µl ALT 188 10–125 U/l MPV 13.8 8.7–13.2 fl Total bilirubin 1.1 0.0–0.9 mg/dl Case 2 Monocytes 0.064 0.15–1.35 K/µl Cholesterol 413.9 135–270 mg/dl Mixed Eosinophils 0 0.1–1.5 K/µl ALT 157 21–102 UI/l Fructosamine 488.9 192.6–357.4 µmol/l ALKP 290 20–156 UI/l Case 3 Potassium 3.94 4.37–5.35 mmol/l YT Sodium 135.5 141–152 mmol/l Chlorine 99.1 105–115 mmol/l (RDW): Red cell distribution width; (MPV): Medium platelet volume; (ALT): Alanine aminotransferase; (ALKP): Alkaline phosphatase. Table 3. Metrics of the peristaltic phacoemulsification procedures of three dogs postoperatively affected by UZS. Eye Time (minutes) Power (%) Energy (%-seg) Fluids (ml) OD 3.27 28.70 93.80 229 Case 1 OS 3.55 29.50 104.72 210 OD 4.01 26.70 106.80 194 Case 2 OS 3.55 31.50 111.82 208 OD (non-affected) 3.03 34.50 104.53 149 Case 3 OS 3.04 36.50 110.96 158 Table 4. VTH-UAB protocol for managing postoperative IOP spikes in dogs. < 20 mmHg • Follow the prescribed traetment • NON-CARDIAC PATIENT: Apply one drop of dorzolamide + timolol 20-30 mmHg • CARDIAC PATIENT: Apply one drop of dorzolamide • Recheck IOP in one hour • Apply one drop of latanoprost 30-40 mmHg • Recheck IOP in one hour • Manual ACD through corneal incision (Hildebrand et al., 2003) > 40 mmHg • Recheck IOP in one hour aqueous flare, centered intraocular lens (IOL), and rechecks, despite the use of latanoprost, mydriasis normal fundus examination. The hypertensive eyes was still present in dogs one and two OU and in dog (n = 4) were treated with a drop of latanoprost three OS. Based on the presence of the three classical (Xalatan®, Pfizer, New York, NY), and IOPs rechecked signs (mydriasis, iris atrophy, and glaucoma), UZS was after 30 minutes. IOP dropped down to normal values; diagnosed in the three dogs, being initially classified as thus, latanoprost was added to the previous treatment, severe for case 1 OU and case 3 OS and moderate for and tropicamide was discontinued. In the following case 2 OU. 141 http://www.openveterinaryjournal.com F. Cantero et al. Open Veterinary Journal, (2022), Vol. 12(1): 138–147 Fig. 1. Images of diabetic dogs affected by UZS. (A): Fixed, severely dilated pupils in a 9-year-old mixbreed dog, 1-week after bilateral cataract surgery. (B): Fixed moderately dilated pupils (OS>OD) in a IWH, 2-week after bilateral cataract surgery. (C): Fixed severely dilated left pupil in a YT dog, 1-week after bilateral cataract surgery. Dogs from figures A and B showed preoperative mild iris atrophy but normal PLRs. Long-term postoperative treatment and outcome movement was observed. Along with postoperative Two weeks after the surgery, case 1 was rechecked due rechecks, pupils remained dilated, and IOP spikes in to a sudden episode of blindness. Menace response and both eyes required further management with mannitol dazzle reflex were absent, and pupils rested at the same iv (Mannitol Mein 20%®, Fresenius SE&Co, Bad severe mydriatic status. IOPs were 70 mmHg OD and Homburg v.d.H., Germany) and topical combination 56 mmHg OS. Dynamic gonioscopy (17 mm Koeppe of brinzolamide and brimonidine (Simbrinza®, Alcon goniolens®, Ocular Instruments Inc., Washington, DC) Healthcare, Barcelona, Spain). At the time of writing confirmed the closure of the ICA due to a complete this paper, menace response was only present OS with peripheral anterior synechia. Options were discussed both pupils severely mydriatic and unresponsive to with the owners, and an intraocular surgery was light. IOPs at that moment were 7 mmHg OU, and the performed for breaking synechiae. Surgery occurred dog was under topical medication with brinzolamide/ uneventfully, but although intracameral acetylcholine brimonidine q6h and latanoprost q12h, as well as was injected in both eyes (Acetilcolina 10 mg/ml with systemic citicoline (15 mg/kg PO; Neuro-CPD®, cusí®, Alcon Healthcare, Barcelona, Spain), no pupil Vetilea SL, Barcelona, Spain). 142 http://www.openveterinaryjournal.com F. Cantero et al. Open Veterinary Journal, (2022), Vol. 12(1): 138–147 Similarly, case 2 was reviewed 3 weeks after the surgery (Bilotta and Busse, 2021; Michau, 2021). Nevertheless, due to severe discomfort in the right eye. No menace none of the above were associated with high IOPs. response, dazzle reflex, nor PLRs were observed. UZS, although by no means frequent, has been a OD and IOP were 65 mmHg. Due to the uncomplete well-recognized, postoperative ocular complication response to the systemic medication with mannitol (2 in humans since 1963 (Urrets-Zavalia, 1963). Along g/kg iv) and the topical medication with latanoprost, the last decades, the syndrome, initially described by brinzolamide, and brimonidine, persistent IOP spikes a fixed dilated pupil with iris atrophy and increased lead to a comfortable but blind eye OD. At last recheck IOP, has englobed other clinical presentations, keeping before writing this manuscript, positive menace fixed dilated pupils the main clinical sign (Spierer and response and dazzle reflexes were present OS and Lazar, 2014). Nowadays, UZS has two well-known absent OD, although the pupils remained moderately presentations with varying severity. The milder form mydriatic and unresponsive to light. IOP was16 mmHg is characterized by fixed mydriasis seen as a sole OD and 6 mmHg OS, and the dog were under a topical finding. The pupil dilation may diminish gradually combination of brinzolamide and brimonidine OU q6h in the next month or so until it returns to its normal (Simbrinza®, Alcon Healthcare, Barcelona, Spain) and size. As a rule, the slow process of recovery occurs systemic citicoline. spontaneously, leaving as a sequela diffuse atrophy At last recheck, case 3 showed menace response and of the ante­rior layers of the iris (Spierer and Lazar, dazzle reflex OU, had a moderately mydriatic and 2014; Isac et al., 2019). This form may easily go unresponsive left pupil, and the IOPs were 7 mmHg unnoticed based on the milder clinical findings and the OD and 22 mmHg OS. The dog was under topical mandatory use of postoperative topical mydriatics. A antiglaucoma medication OS (dorzolamide q8h and more severe form of UZS can be seen in less fortunate latanoprost q24h) and systemic citicoline. cases, showing marked fixed mydriasis is accompanied Based on the outcome and the partial pupillary recovery with iris atrophy and increased IOP. In most cases, of the left eye of case 3, severity was reestablished, mydriasis is irreversible and even exaggerated in parts, being considered as severe in two eyes (case 1) and producing at the same time an ectropion of the pigment moderate in three eyes (case 2 and case 3). epithelium at the pupillary border and secondary dyscoria. Invariably, there is also a marked tendency Discussion toward the formation of synechiae. The clinical picture Phacoemulsification is considered as the gold-standard is much reminiscent of that encountered after a severe treatment for cataracts, being routinely performed by attack of high IOP (Magalhães et al., 2016). Despite veterinary ophthalmologists (Michau, 2021). In the the five affected eyes of this case series showing the hands of experienced surgeons, surgical outcomes clinical appearance of iris atrophy and glaucoma, mirror the ones described in human´s ophthalmology, three were initially classified as severe forms of UZS with a low incidence of complications reported (17.3%) based on their fixed severe mydriasis, and two as (Klein et al., 2011). Postoperative complications have moderate forms. Along the postoperative period, one decreased significantly over time due to factors such eye showed partial pupillary improvement, showing as improvement in the patient selection process, tissue more moderate mydriasis, thus being re-classified as handling, use of nondepolarizing neuromuscular a moderate form. blocking agents, adequate preoperative mydriasis, Although UZS has shown no predilection for age, shortened surgical times, type of IOL, and use of gender, or systemic concomitant diseases in humans ophthalmic viscosurgical devices (OVDs), among (Magalhães et al., 2016), the three dogs reported in the others. Immediate postoperative complications present study were diabetic. The role diabetes mellitus described in dogs so far include corneal incision may have played in the development of the condition dehiscence and infection, corneal ulceration, corneal is uncertain; however, considering that vasculitis is a endothelial decompensation and edema, intraocular relatively common complication in diabetic patients hemorrhage, anterior uveitis, fibrin, toxic anterior (Rask-Madsen and King, 2013), it could have helped chamber syndrome, and POH (Michau, 2021). in its development. Without a doubt, the relationship Similarly, the most common long-term postoperative between diabetes mellitus and UZS requires further complications described are corneal lipidosis, investigation. degenerations and ulcerations, endophthalmitis, In human literature, the clinical signs of UZS have posterior and anterior capsule opacification, IOL been reported to appear between 1 and 21 days after decentration or luxation, glaucoma, retinal detachment, the surgery (Totuk et al., 2018; Kurtz and Fradkin, and peripheral ocular neuropathies (Michau, 2021). In 2021). The exact time for the clinical signs to appear addition, conversely to what has been widely described in the present study is unknown, as our first post- in human literature (Galiani and Aminlari, 2002), phacoemulsification recheck was performed 7 days there are only two descriptions of the atonic pupil as after the surgery in all the cases. Even though the a postoperative complication of phacoemulsification clinical signs were evidenced at the first recheck, they 143 http://www.openveterinaryjournal.com F. Cantero et al. Open Veterinary Journal, (2022), Vol. 12(1): 138–147 could have shown before and gone unnoticed by the thus reducing the intraoperative IOP. In the five eyes owner. here reported, a clear corneal incision of 2.8 mm width Although the exact mechanism of UZS is still unknown, was performed, corresponding to the width required by two main etiologies have been historically considered the phacoemulsification needle and infusion sleeve. All overtime. The first, observed after intraocular or non- the eyes underwent a one-handed divide-and-conquer penetrating surgery, seems to be caused by an IOP technique with no significant difference regarding the spike and impairment of the vascular supply to the iris phacoemulsification time, power, and volume of fluids constrictor muscle, leading to iris atrophy with subsequent used when compared to other cataracts of the same persistent pupil dilation (Tuft and Buckley, 1995). The degree of maturity in the same institution. IOP spike, if short, could induce the milder form of the Similarly, immediate postoperative spikes have been presentation (with mydriasis as the sole clinical sign), associated with different factors, such as OVDs while if maintained over time, it could induce the more retention in the anterior chamber angle, preexisting severe form of the syndrome (mydriasis, iris atrophy, compromise of outflow facility, surgical trauma, and glaucoma). The second etiology, observed after hyphema, inflammation, and the skillfulness of the 360-degree laser procedures, would seem to be caused surgeon (Michau, 2021). In the present study, besides by impairment of the parasympathetic pathway to the cohesive OVDs were routinely removed from the iris constrictor muscle, related to direct laser damage anterior chamber and lenticular bag, moderate-to- to the short ciliary nerves that run radially from the severe IOP spikes were detected in all the affected eyes posterior pole toward the iris sphincter muscle (Vieira throughout the first 24 postoperative hours. Surprisingly, et al., 2017). This form does not involve iris atrophy or those spikes were higher in the most severely affected secondary glaucoma, and thus we believed we should eyes, requiring repeated ACD to return to normal IOP avoid grouping all the cases of fixed and dilated pupils values. Postoperative IOP spikes have been previously under the same syndrome, as they do not have neither associated with ocular blood flow dysregulation and the same signs nor the same etiology. Thus, we suggest tissue ischemia (Tranos et al., 2013). Elevated and another syndrome should be defined to cover the cases maintained IOP combined with a low systemic blood in which the fixed and dilated pupil was not caused by pressure has been shown to reduce the ocular perfusion iris ischemia precipitated by an IOP spike but by the pressure, thus inducing tissue ischemia (Costa et al., direct impairment of the parasympathetic pathway to 2014). Unfortunately, no blood pressure measurements the iris constrictor muscle. The five eyes reported in the were taken during the immediate postoperative period; present study showed moderate to severe immediate thus, this hypothesis could not be confirmed. POH which could have triggered the syndrome. In The five ocular surgeries were uneventfully performed by fact, the eye with milder clinical signs of UZS was the experienced surgeons, and no preexisting compromise one with lower POH values, needing just one ACD for of outflow facility was detected by gonioscopy in none reestablishing normal IOP. of the eyes. Several studies compare the outcomes of Different mechanisms could induce IOP spikes during cataract surgery in relation to POH. A study on the use the intraoperative or immediate postoperative period. of ultrasound biomicroscopy to investigate angle and Intraoperatively, the IOP could inadvertently rise as a globe morphology before and after phacoemulsification result of OVDs. Studies comparing the effect of various in dogs concluded that dogs with larger ICA and AOD viscoelastic formulations on postoperative pressure in measurements before surgery were at greater risk of humans undergoing cataract surgery abound in the developing POH (Rose et al., 2008). Another recent literature with various conclusions (Henry and Olander, study revealed that eyes with abnormal gonioscopy 1996). Although significant pupil atrophy has not been findings are at an increased risk of postoperative reported after the widespread use of OVDs in cataract glaucoma compared with eyes with normal gonioscopy extraction surgery, the IOP increase related to the use of findings (Sanders et al., 2021). Therefore, gonioscopy OVDs during intraocular surgery has been postulated is recommended as a part of the presurgical assessment as a reason for UZS (Tan and Humphry, 1993; Bourcier in all dogs before phacoemulsification. et al., 2001). Apart from the mechanical vascular Although TASS has been reported to be a risk factor for compression, OVDs may cause a toxic effect, resulting developing UZS in humans (Nizamani et al., 2013), the in ischemia and, consequently, fixed and dilated degree of postoperative intraocular inflammation seen pupils. Another critical point for intraoperative IOP in those eyes was considered as normal, with mild to increase is the phacoemulsification fluidics. Studies moderate degree of aqueous flare that improved with have reported that the different phacoemulsification medical treatment along the postoperative period. approaches, the influx of irrigation fluid into the eye, Although the use of mydriatics, more specifically, and the efflux of the fluid through the side port and atropine, has been classically postulated as an etiology corneal incision site influence the IOP (Wilbrandt for UZS, none of the dogs of this study were treated with and Wilbrandt, 1993; Kang et al., 2015). In fact, it is topical atropine nor with intracameral phenylephrine. generally believed that maintenance of some incision Mydriatic preoperative medication consisted of topical leakage during the procedure acts as a fluidics buffer, tropicamide and phenylephrine (1%). 144 http://www.openveterinaryjournal.com F. Cantero et al. Open Veterinary Journal, (2022), Vol. 12(1): 138–147 Nowadays, there is no curative treatment for this condition. Aralikatti, A.K., Tomlins, P.J. and Shah, S. 2008. The use of topical parasympathetic (pilocarpine) and Urrets–Zavalia syndrome following intracameral sympatholytic agents (dapiprazole and guanethidine) has C3F8 injection for acute corneal hydrops. Clin. been investigated. Although the majority of studies on Exp. Ophthalmol. 36, 198–199. the use of topical pilocarpine and guanethidine showed Bilotta, T. and Busse, C. 2021. Urrets-Zavalia syndrome no improvement of the fixed and dilated pupils (Bonnet in a dog following cataract surgery. ECVO 2021 et al., 1969; Bourcier et al., 2001; Espana et al., 2007; Annual conference meeting. Kaeser and Kawasaki, 2010), when both combined, Bonnet, M., Lemarchands, H. and Martin, J. 1969. they were able to partially treat sympathetic spasm Prevention and treatment of the “irreducible and induce miosis (Lagoutte et al., 1983). Similarly, mydriasis-progressive atrophy of the iris” syndrome dapiprazole was successfully used for restoring pupil following perforating keratoplasty for keratoconus. size in a patient with UZS after a keratoplasty procedure Ann. Ocul. 202, 1139–1146. (Spadea et al., 2008). In parallel, several reconstructive Bourcier, T., Laplace, O., Touzeau, O., Moldovan, surgical treatments have been described in humans S.M., Borderie, V. and LarochE, L. 2001. Urrets- for symptomatic permanent mydriasis. These include Zavalia syndrome. J. Fr. Ophtalmol. 24, 303–308. keratopigmentation (Reed, 1994; Alio et al., 2012), Bozkurt, K.T., Acar, B.T. and Acar, S. 2012. Fixed a black diaphragm intraocular lens (Sundmacher dilated pupil as a common complication of et al., 1994), and pupilloplasties (Ogawa, 1998; Narang deep anterior lamellar keratoplasty complicated et al., 2017). At the time of writing this report, three with descemet membrane perforation. Eur. J. eyes remained still visual, all under topical antiglaucoma Ophthalmol. 23, 164–170. drugs. None of them responded to topical pilocarpine Chelnis, J.G., Sieminski, S.F. and Reynolds, J.D. 2012. or latanoprost during the study period, maintaining Urrets-Zavalia syndrome following goniotomy in a mydriasis. No overt signs of photophobia were observed. child. JAAPOS 16, 312–313. To summarize, this is the first published description Costa, V.P., Harris, A., Anderson, D., Stodtmeister, R., of UZS in dogs, occurring after phacoemulsification Cremasco, F., Kergoat, H., Lovasik, J., Stalmans, I., surgery. Even though no exact, demonstrable causative Zeitz, O., Lanzl, I., Gugleta, K. and Schmetterer, L. element could be determined, we believe that the use 2014. Ocular perfusion pressure in glaucoma. Acta of ocular viscoelastic devices or topical tropicamide/ Ophthalmol. 92, 252–266. phenylephrine was not directly associated with the Espana, E.M., Ioannidis, A., Tello, C., Liebmann, onset of UZS. Conversely, POH should be considered J.M., Foster, P. and Ritch, R. 2007. Urrets-Zavalia a triggering condition for this syndrome, as it directly syndrome as a complication of argon laser peripheral affects the blood flow autoregulation and intrinsic uveal iridoplasty. Br. J. Ophthalmol. 91, 427–429. tissue integrity. Until the contrary is proved, diabetes Foroutan, A., Tabatabaei, S.A., Soleimani, M. and mellitus might be considered a risk factor for developing Nekoozadeh, S. 2016. Urrets-Zavalia syndrome this syndrome after cataract surgery in dogs. in different methods of keratoplasty. Int. J. Conflict of interest Ophthalmol. 9, 1358–1360. The authors declare that there is no conflict of interest. Fournié, P., Ponchel, C., Malecaze, F. and Arné, J.L. Author contributions 2009. Fixed dilated pupil (Urrets-Zavalia syndrome) Marta Leiva, Francisco Cantero, and Laura Gaztelu did and anterior subcapsular cataract formation after the diagnosis, provide key information and analyzed descemet stripping endothelial keratoplasty. Cornea the data. Francisco Cantero and Marta Leiva designed 28, 1184–1186. the manuscript, wrote the original draft, and revised Galiani, D.L. and Aminlari, A. 2002. Atonic pupil it critically for important intellectual content. All the following cataract extraction: incidence over a ten- authors had direct patient contact, revised, edited the year period. ARVO Ann. Meet. Abs. 43, 386–386. manuscript, and gave their final approval for the version Henry, J.C. and Olander, K. 1996. 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