Veterinary Ophthalmology - 2016 - Barbé - Marsupialization of a cyst of the nictitating membrane in three dogs.pdf

Veterinary Ophthalmology (2017) 20, 2, 181–188 DOI:10.1111/vop.12382 CASE REPORT Marsupialization of a cyst of the nictitating membrane in three dogs Charlotte Barb
e,* Isabelle Raymond-Letron,†,‡ Guillaume-Pierre Mias,§ Julien Charron§ and Fr
ed
eric Goulle* *Clinique v
et
erinaire AQUIVET, Parc d’...

Veterinary Ophthalmology (2017) 20, 2, 181–188 DOI:10.1111/vop.12382 CASE REPORT Marsupialization of a cyst of the nictitating membrane in three dogs Charlotte Barb
e,* Isabelle Raymond-Letron,†,‡ Guillaume-Pierre Mias,§ Julien Charron§ and Fr
ed
eric Goulle* *Clinique v
et
erinaire AQUIVET, Parc d’activit
es Mermoz, 19 avenue de la for^et, 33320, Eysines, France; †INP – ENVT, universit
e de Toulouse, 23 chemin des Capelles – BP 87614, 31076 Toulouse, Cedex 03, France; ‡STROMALab UMR 5273 UPS EFS INSERM U1031, 1 avenue Jean Poulhes, 31403 Toulouse, France; and §Clinique v
et
erinaire SAINT–ROCH, 18 rue de Dompierre, 17000 La Rochelle, France Address communications to: F. Goulle Tel.: +33(0)5 56 95 01 01 Fax.: +33(0)5 56 28 67 25 e-mail: [email protected] Abstract Background Development of cysts has been reported as a potential complication after surgical repositioning of nictitating membrane gland protrusion using the conjunctival pocket technique. To the authors’ knowledge, no treatment for these cysts has ever been published. Objectives This short case series describes a surgical technique of marsupialization as a treatment option for these cysts and proposes a pathogenesis for cyst formation. Cases description Three dogs were each referred for a unilateral subconjunctival mass-like lesion involving the bulbar side of the nictitating membrane. Complete ophthalmologic examination revealed a pink, translucent, soft, and nonpainful mass protruding from the bulbar surface of the nictitating membrane in all cases. Treatment consisted in marsupialization of the cyst on the palpebral surface of the nictitating membrane and was curative with no short-term postoperative complication and favorable long-term outcome for the three dogs. Histopathological findings were consistent with a lacrimal cyst. Conclusion Marsupialization appears to be a safe, simple, and effective treatment for nictitating membrane cyst secondary to surgical correction of gland prolapse using conjunctival pocket technique in dogs. Further studies on a larger number of cases are necessary to determine whether marsupialization is the technique of choice and to further investigate the pathophysiology of cyst formation after conjunctival pocket repositioning of prolapsed glands. Key Words: canine, cyst, marsupialization, nictitating membrane, pocket technique INTRODUCTION Protrusion of the third eyelid gland, also referred to as prolapse of the nictitating membrane gland (NMG), is the most common primary disorder of the third eyelid gland in dogs.1 As a strong breed predisposition is noted in cocker spaniel, beagle, basset hound, Boston terrier, Lhasa apso, shih tzu, Pekingese, bulldog, shar-pei, Neapolitan mastiff, and Newfoundland,2–5 a genetic defect is suspected. The mode of inheritance, which appears to be complex and potentially multigenic, remains to be determined.5 The exact pathogenesis of this condition has not © 2016 American College of Veterinary Ophthalmologists been elucidated. Several etiological mechanisms have been proposed, including a weakness or laxity in the connective tissue anchoring the NMG to the periorbital tissues and a lymphoid hyperplasia.1,4,6,7 Definitive treatment of the nictitating membrane gland prolapse (PNMG) is surgical. Prolapsed glands should be replaced rather than excised owing to the gland’s contribution to tear production.4 This is especially important in breeds predisposed to keratoconjunctivitis sicca.7–9 The nictitating membrane (NM) also provides physical protection of the cornea and is an important contributor to the secretory immune system.10 Recently, Saito found that AL. third eyelid removal decreased lacrimation of 26% within 3–7 months but, after 1 year, values recovered to near normal.11 There was also a decrease in tear breakup time, positive vital staining, and morphologic changes of the corneal epithelium, which indicated a lack of barrier function.12 These findings definitively support the recommendation of preserving, as often as possible, the nictitating membrane and its gland. A number of surgical techniques for PNMG correction have been described, including the anchor suture techniques, the conjunctival pocket technique, and the Kaswan technique.3,7,13–17 A commonly used technique is the pocket technique initially described by Moore and then modified by Morgan.7 A possible complication of PNMG correction by conjunctival pocket technique is formation of a conjunctival cyst. The suspected pathogenesis is that cystic accumulations of tear fluid may form beneath the conjunctiva of the NM if the incisions are connected.1 However, lacrimal cyst formation may also occur in any location where lacrimal tissue is present.18 The exact pathogenesis is unclear. Mechanical or passive dilatation of excretory ducts by inflammation or trauma may lead to a retention cyst.19–21 In the Morgan technique, burying a portion of conjunctival epithelium may lead to formation of a conjunctival cyst.7 Conjunctival cysts may occur after traumatic displacement of epithelial tissue which then develops into a cystic lesion. This may occur after surgery or trauma.22 To the authors’ knowledge, no treatment for these cysts has previously been published. Surgical excision of lacrimal gland cyst (dacryops) is curative.19,20,23,24 However, lacrimal secretion can be compromised depending on the amount of lacrimal gland excised. In human, marsupialization is indicated in cases associated with hypolacrimation and is a safe and effective modality in the management of dacryocoeles, dacryops, and canaliculops.21,25–29 The purpose of this short case series was to describe a surgical technique of marsupialization for lacrimal cyst of the NM (LCNM), to present short-term postoperative complications and long-term outcome on three dogs treated with this procedure, and to propose a pathophysiology for their formation. Schirmer tear test 1 (standardized sterile strips; Merck animal health, Summit, NJ, USA), staining test with fluorescein (Fluorescein 0.5%TM unidose; TVM, Lempdes, France), and indirect ophthalmoscopy for fundic examination (Omega 500TM and 20D lens; Heine, Herrsching, Germany), was performed. Moderate protrusion and enlargement of the right NM along with conjunctival hyperemia was noted. A soft, pink, translucent subconjunctival mass, 15 mm in diameter, protruded from the bulbar surface of the right NM. The mass extended from the base to the leading edge of the NM (Figure 1). Schirmer tear test 1 readings were 15 mm/min OD and 21 mm/min OS. Intraocular pressures were 15 mm Hg OD and 11 mm Hg OS. The staining test with fluorescein was negative OU. Slit-lamp biomicroscopy revealed no significant abnormalities of the cornea, the anterior chamber, or the lens. No changes were noted on funduscopic examination after tropicamide instillation (Mydriaticum 0.5%TM; Thea, Milan, Italy). Differential diagnosis of this cystic lesion included lacrimal cyst, conjunctival cyst, mucocoele, abscess, suture reaction, cystic tumors, dermoid/epidermoid cyst, and parasitic cyst. Fine-needle aspiration, using a 23G gauge needle mounted on a 5-mL syringe, was performed under local anesthetic with oxybuprocaine hydrochloride (Cebesine 0.4%TM; Chauvin laboratories, Montpellier, France). The conjunctival sac was irrigated with 10% povidoneiodine (VetedineTM; Vetoquinol, Lure, France) diluted in sterile lactate ringer solution using a 1:50 ratio. The cyst was completely drained, yielding 1.5 mL of a viscous transparent fluid. Cytological examination was compatible with nonseptic lacrimal fluid. On the basis of the historical, clinical, and cytological findings, a presumptive diagnosis of lacrimal cyst of the nictitating membrane (LCNM) was established. CASES DESCRIPTION Clinical presentation Dog 1 A 10-month-old male French bulldog was referred to the institution AQUIVET with a 4-month history of swelling of the right NM. Significant ophthalmic history included previous surgery for prolapse of the gland of the NM. A conjunctival pocket technique was performed 4 months previously by the referring veterinarian. A complete ophthalmic examination, using slit-lamp biomicroscopy (Hawkeye, Dioptrix, Toulouse, France), rebound tonometry (Tonovet; i care, Vantaa, Finland), Figure 1. Case 1: Appearance at initial presentation. Close up view of OD showing NM enlargement, moderate conjunctival hyperemia, and the absence of corneal lesion. © 2016 American College of Veterinary Ophthalmologists, Veterinary Ophthalmology, 20, 181–188 14635224, 2017, 2, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/vop.12382 by Robin Stanley - National Health And Medical Research Council , Wiley Online Library on [22/05/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 1 8 2 b a r b
e E T Surgery for creation of a permanent stoma was recommended but declined by the owner. Topical indomethacin 0.1% drops twice daily (IndocollyreTM 0.1%; Chauvin laboratories, Montpellier, France) and fusidic acid gel three times daily (Fucithalmic vetTM; Dechra, Uldum, Denmark) onto the right eye were prescribed for 2 weeks. The owner was aware of the significant risk of recurrence of the cystic mass. Three weeks following initial presentation, recurrence of the cyst occurred and marsupialization of the cystic structure was planned. Dog 2 A 6-month-old female English bulldog was referred to the institution AQUIVET with a 3-month history of a pink mass associated with the right nictitating membrane, occasioning moderate discomfort, and persistent ocular inflammation. The dog’s ophthalmic history included surgical replacement of prolapsed NMG 3 months earlier by the referring veterinarian, using the conjunctival pocket technique.7 A slow growing mass associated with the NM appeared following surgery with a concomitant blepharospasm (Figure 2). Complete ophthalmic examination of the right eye revealed the presence of a fluctuant swelling protruding from the bulbar surface of the nictitating membrane. Marked conjunctival hyperemia and protrusion of the NM were present and were associated with a slight mucopurulent discharge. Some follicles were also noted on the palpebral surface of the nictitating membrane. The nictitating membrane was then everted, and a large prominent mass extending from its base to its leading edge was visualized. Upon palpation, the mass appeared soft and nonpainful. Partial dehiscence of the prior surgical wound closure performed by the referring vet was noted on the bulbar and medial aspect of the nictitating membrane. Figure 2. Case 2: Appearance at initial presentation. Close up view of OD showing severe NM enlargement, marked conjunctival hyperemia, and slight mucopurulent epiphora. Schirmer tear test 1 readings were 11 mm/min OD, which was judged abnormally low, and 21 mm/min OS.24 Intraocular pressures were 15 and 16 mmHg for the right and the left eyes, respectively. The staining test with fluorescein was negative, and the slit-lamp biomicroscopy revealed no significant abnormalities of the cornea, the anterior chamber, or the lens. No lesion was noted on funduscopic examination after tropicamide instillation. Differential diagnoses were the same as those previously enounced. Fine-needle aspiration of the mass was performed as previously described, and 3 mL of fluid was aspirated. Cytological examination was compatible with a nonseptic lacrimal fluid. Probably, the diagnosis was determined to be lacrimal cyst of the NM. Marsupialization of the cyst was recommended and planned. At pending surgical intervention, a medical treatment was initiated with indomethacin drops (Indocollyre 0.1%TM) twice daily, artificial tear substitutes (ViskyalTM; TVM, Lempdes, France) three times daily, and fusidic acid gel (Fucithalmic vetTM) three times daily onto the right eye for 7 days. Dog 3 A 4-year-old female English bulldog was presented at the institution SAINT-ROCH with a history of recurrent mass on the left nictitating membrane after its surgical replacement by the referring vet 3.5 years earlier using the conjunctival pocket technique. Successful surgical replacement of a right nictitating gland prolapse was also performed when the dog was 5-month old using the same technique. As part of the left eye’s medical history, marked conjunctivitis was observed within the first 2 weeks following nictitating gland surgery, which was successfully treated with a combination of framycetin and dexamethasone phosphate ointment (FradexamTM; TVM, Lempdes, France) three times daily for 2 weeks. Within the 3 months after surgery, the dog developed a fluid-filled mass on the left nictitating membrane, which was aspirated monthly for 3 months with an adjunctive anti-inflammatory treatment (FradexamTM). The dog was lost to follow up by the referring vet for eighteen months before being referred. Upon admission, a complete ophthalmologic examination was completed. The dog had a subconjunctival fluctuant mass on the bulbar surface of the left nictitating membrane. Moderate protrusion of the NM was present with slight mucopurulent discharge and mild blepharitis. Eversion of the NM revealed a soft nonpainful mass, 20 mm in diameter, extended from the base of the NM to its leading edge. Schirmer tear test 1 readings were 19 mm/min OD and 16 mm/min OS. Intraocular pressures were 18 and 16 mm Hg for the right and the left eyes, respectively. The slitlamp biomicroscopy revealed a mild keratitis OS with slight corneal neovascularization and edema on the superonasal quadrant (Figure 3). The staining test with fluorescein was negative. Fundic examination was within normal limits. © 2016 American College of Veterinary Ophthalmologists, Veterinary Ophthalmology, 20, 181–188 14635224, 2017, 2, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/vop.12382 by Robin Stanley - National Health And Medical Research Council , Wiley Online Library on [22/05/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License marsupialization of nictitating membrane cyst 183 AL. Aspiration of the fluid-filled mass was performed as previously described. Two milliliters of a translucent fluid was obtained. Cytological examination revealed moderate quantity of nondegenerative neutrophils and lymphocytes consistent with chronic inflammation. No intracellular bacteria were visible. A presumptive diagnosis of lacrimal cyst of the NM was made, and marsupialization of the cyst was recommended and planned. Surgical technique After premedication with 10 lg/kg buprenorphine (BuprecareTM; Axience, Pantin, France) and 0.5 mg/kg diazepam (ValiumTM; Roche, Boulogne-Billancourt, France), general anesthesia was induced with 3.5 mg/kg propofol (PropovetTM; Axience, Pantin, France) intravenously and maintained with isoflurane (Iso-vetTM; Piramal Healthcare, Morpeth, Northumberland, UK). The dog was positioned in lateral recumbency with the nose slightly elevated. The periocular skin of the affected eye was cleaned with 10% povidone-iodine (VetedineTM) diluted in sterile lactate ringer solution using a 1:20 ratio, and the conjunctival sac was flushed using a 1:50 ratio. The surgical microscope Figure 3. Case 3: Appearance at initial presentation. Close up view of OS showing NM enlargement, conjunctival hyperemia, corneal neovascularization, and edema on the superonasal quadrant. (a) (OMS600TM; Topcon, Tokyo, Japan) was positioned, and the patient was draped routinely. One stay suture of 5–0 polypropylene (ProleneTM; Ethicon, Livingston, Scotland) was placed through palpebral conjunctiva of the nictitating membrane and then grasped to facilitate manipulation of the NM and provide access to the bulbar surface (Figure 4a). A number 11 scalpel blade was used to perform a horizontal linear incision over the cystic mass on the ventral palpebral surface of the NM (Figure 4b). Blunt dissection of the conjunctiva, using rounded Stevens tenotomy scissors, was continued lateral to the ‘shaft’ of the hyaline cartilage, until the wall of the cyst was reached. A fullthickness linear incision of the cyst wall was performed using the scalpel blade and scissors (Figure 5a). The surgical site was flushed using sterile lactate ringer solution. Marsupialization was created by suturing the wall of the cyst to the adjacent NM conjunctiva in a simple interrupted suture pattern using a 6–0 coated braided lactomer 9-1 (PolysorbTM; Covidien; Mansfield, MA, USA) suture material in cases 1 and 2 (Figure 5b) and 6/0 polyglyconate (MonosynTM; B/Braun surgical, Rubi, Spain) suture material in case 3. Diagram 1 summarize the surgical steps. In case 2, a standard conjunctival pocket technique, as previously described by Morgan, was added to replace the protruded NMG.7 In case 3, fluid was collected for bacteriological examination and a piece of the wall of the mass was submitted for histological examination. Each dog was discharged on the same day with an Elizabethan collar. In cases 1 and 2, oral 10 mg/kg of body weight amoxicillin potentiated with 2.5 mg/kg of body weight clavulanic acid (ClavaseptinTM; Vetoquinol, Lure, France) was administered postoperatively twice daily for 10 days and topical tobramycin 0.3% drops (Tobrex 0.3%TM; Alcon, Barcelona, Spain) was prescribed three times daily for 10 days onto the affected eye. In case 2, additional topical treatments included indomethacin drops (Indocollyre 0.1%TM) twice daily, for 10 days onto the affected eye and artificial tear substitutes (ViskyalTM) three times daily for life onto both eyes. In case 3, postoperative medical treatment only consisted of topical fusidic acid gel (Fucithalmic vetTM) three times daily onto the left eye for 10 days. The owners were instructed to restrict the dog’s activity for 2 weeks. (b) Figure 4. Case 2: Intra-operative photographs. (a) Bulbar face of the NM everted, showing cyst protrusion through the wound dehiscence. (b) Horizontal incision on the ventro-palpebral surface of the NM. © 2016 American College of Veterinary Ophthalmologists, Veterinary Ophthalmology, 20, 181–188 14635224, 2017, 2, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/vop.12382 by Robin Stanley - National Health And Medical Research Council , Wiley Online Library on [22/05/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 1 8 4 b a r b
e E T (a) (b) Figure 5. Case 2: Intra-operative photographs. (a) Cyst wall, protruding through the incision after blunt dissection. (b) Completion of the simple interrupted suture of the cyst wall to the surrounding NM conjunctiva. (a) (b) (c) (d) (e) Diagram 1. LCNM marsupialization technique of Goulle: (a) A linear conjunctival incision on the ventral palpebral surface of the NM was performed. (b) Blunt dissection of the conjunctiva was continued lateral to the ‘shaft’ of the hyaline cartilage. (c) A full-thickness linear incision of the cyst wall was performed. (d) Incision was enlarged using scissors. (e) Marsupialization was created by suturing the wall of the cyst to the adjacent NM conjunctiva in a simple interrupted suture pattern. Results and follow-up Dog 1 Two weeks following surgery, ophthalmic examination revealed minimal swelling of the palpebral side of the right NM conjunctiva and the absence of eye discharge. Schirmer tear test 1 readings were 16 mm/min and 20 mm/min on the right and the left eyes, respectively. The rest of the ophthalmologic examination was within normal limits. Examination of the surgical site revealed that the stoma site remained patent. The owner was contacted by phone 2 years after the surgery and did not report recurrent ocular problems. © 2016 American College of Veterinary Ophthalmologists, Veterinary Ophthalmology, 20, 181–188 14635224, 2017, 2, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/vop.12382 by Robin Stanley - National Health And Medical Research Council , Wiley Online Library on [22/05/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License marsupialization of nictitating membrane cyst 185 AL. Information about eye comfort, blinking, rubbing, redness, need for cleaning, or protrusion of the nictitating membrane was elicited. The owner reported that eyes were comfortable with neither conjunctival redness nor mucous discharge that may indicate chronic inflammation or keratoconjunctivitis sicca. Dog 2 Two weeks postoperatively, moderate hyperemia of the right palpebral NM conjunctiva was observed without blepharospasm or discharge. Schirmer tear test 1 readings (17 mm/min OD and 18 mm/min OS) were within normal limits. Slit-lamp biomicroscopy was unremarkable. The conjunctival stoma remained patent. Two months after surgery, there was no evidence of cyst recurrence. Schirmer tear test 1 readings were 17 mm/min OD and 20 mm/min OS. The stoma site was patent (Figure 6). Dog 3 Two weeks after surgery, moderate hyperemia and swelling of the left palpebral NM conjunctiva were present. Moderate mucopurulent discharge was also noted. Schirmer tear test 1 readings were 17 mm/min OD and 14 mm/min OS. Slit-lamp biomicroscopy revealed improvement of the keratitis with a significant decrease in corneal edema and neovascularization. The rest of the ophthalmologic examination was within normal limits. The conjunctival stoma remained patent. Five and seven weeks following surgery, there was no evidence of cyst recurrence but the NM was still mildly protruding. Keratitis resolved and the Schirmer tear test 1 readings were 18 mm/min OD and 22 mm/min OS. Bacteriological and histological analysis Aerobic and anaerobic bacterial cultures were both negative on case 3 Tissue specimen was fixed in 10% buffered Figure 6. Case 2: Postoperative photograph at 2 months. formalin, routinely processed for histological evaluation, and stained with hematoxylin-eosin (HE) and periodic acid–Schiff (PAS). Tissue sections were also submitted for immunohistochemical assessment for cytokeratin (clone MNF116; Dako, Les Ulis, France), vimentin (clone Vim9; Dako), and smooth muscle actin (clone HHF35; Dako), as previously described by a commercial immunoperoxidase technique using diaminobenzidine chromogen.30 At low power magnification, the cyst wall sample consisted of a thick collagenic connective tissue lined externally and internally by epithelial linings. The external layer of the cyst wall was composed of stratified squamous epithelium, with rare PAS-positive goblet cells. The underlying stroma showed a dense infiltration by numerous neutrophils, lymphocytes, and plasma cells. Under the mucosa, some lacrimal acinar structures were present in the collagenic connective tissue with some neutrophils, lymphocytes, and plasma cells. The internal side of the cyst wall was composed of a discrete lining of flattened cells. The external conjunctival and internal cyst linings as well as the lacrimal lobules were positive for cytokeratin labeling. Immunostaining of both superficial and deep layers was negative for vimentin and a-smooth muscle actin. These microscopic findings support a conjunctival external border of the sample and an internal epithelial lining of the cyst lumen, probably of lacrimal origin. DISCUSSION This report describes for the first time marsupialization of lacrimal cysts of the nictitating membrane gland (LCNM) secondary to surgical repositioning of NMG prolapse by conjunctival pocket technique in three dogs with very similar clinical and follow-up features. A tubuloacinar lacrimal gland surrounds the ventral portion of the cartilage shaft of the NM and excretory ducts open between lymphoid nodules on its bulbar surface.13,31 Prolapse of the nictitating membrane gland (PNMG) is the most common primary disorder of the NM.1 Due to chronic exposure, the prolapsed gland may enlarge and secondary inflammation and infection are frequent.3,4,7 The current treatment of choice for the PNMG is surgical repositioning. The pocket technique described by Moore and Morgan is a common technique used and has a high success rate of 94%.7,13 In a previous study, excretory ducts of the lacrimal gland of the NM were not disturbed following surgical treatment by the posterior pocket technique.13 However, possible complication of PNMG correction by conjunctival pocket technique includes cyst formation.1 Differential diagnosis of cystic lesion of the NM includes lacrimal cyst, conjunctival/epithelial cyst, dacryocoele, abscess, suture reaction, cystic tumors, dermoid/ epidermoid cyst, and parasitic cyst. Histological analysis performed in case 3 and clinical aspect of cavity filled by lacrimal fluid in all the cases were consistent with a © 2016 American College of Veterinary Ophthalmologists, Veterinary Ophthalmology, 20, 181–188 14635224, 2017, 2, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/vop.12382 by Robin Stanley - National Health And Medical Research Council , Wiley Online Library on [22/05/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 1 8 6 b a r b
e E T lacrimal cyst. Lacrimal cyst formation may occur in any location where lacrimal tissue is present. Possible causes include developmental defects, blunt trauma, foreign body injury, or inflammation affecting the ducts.24 Cysts originating primarily from lacrimal glandular or ductal tissue (dacryops) are rare but reported in dogs.19,20,23,24,32–38 Diagnostic confirmation of a lacrimal cyst can be made by histology; immunohistochemical staining for smooth muscle actin labels contractile myoepithelial cells of the outer lining of a normal lacrimal gland. With either conjunctival or lacrimal gland cyst enlargement, the lining may become attenuated and the myoepithelial cells may disappear, making differentiation between these two entities difficult.18–21 Conjunctival cysts are characterized by stratified squamous epithelium with possible goblet cells and a mucinous content.22,39–41 In our case, the slight ductular retention observed was consistent with a lacrimal cyst even with the absence of myoepithelial lining. The presence of an epithelium lining ruled out the diagnosis of dacryocoele. Dacryocoele is not a truly cystic lesion; leakage of tear into the surrounding tissue creates an inflammatory connective tissue lining with no visible epithelium.22 Nictitating membrane gland is important in maintaining normal tear production.4,7,11 The principal lacrimal gland may be the main source of tears in some dogs, whereas it is the NMG in others.8 Keratoconjunctivitis sicca developed in 14.2% of dogs treated with surgical replacement of the gland, but in 48.1% of dogs in which the gland was excised and in 42.8% of dogs left untreated.7 Interestingly, in the two-first cases of our report, initial STT readings were in the low normal range for the affected eye, decreased from about 28.5% in the first case and from 47.6% in the second case, in comparison with the fellow eye. This decrease in lacrimation was possibly due to the imprisonment of tears. The clinical findings in these cases correlated well with the 29–57% reduction of STT readings described by Helper in case of excision of the NMG.8 In the third case, a reduction of only 15.8% of the lacrimal production was present in the affected eye prior to marsupialization, in comparison with the fellow eye. This result could be explained by the previous surgical replacement of PNMG and consequently a decrease in lacrimation in both eyes.7 To the authors’ knowledge, marsupialization of lacrimal cysts has never been described in dogs. Given that our immediate surgical results and long-term follow-up were favorable, marsupialization appeared to be a safe, simple, and effective treatment for LCNM secondary to surgical correction of NMG prolapse using conjunctival pocket technique in dogs. Normalization of STT readings and the absence of visible corneal epithelium alteration after surgical marsupialization suggest that NMG is still functional and that tears flowing out by the palpebral surface play their role. This report is subject to limitations, including the small number of cases evaluated and its retrospective design. CONCLUSION In this short case series, marsupialization was curative with preservation of the nictitating membrane function and good cosmetic results. No short-term complications were observed, and no recurrence of cystic formation was reported on long-term follow-up. Further studies on a larger number of cases will be needed to better document these cysts and could use advanced imaging, histology, and immunostaining evaluations to determine the precise origin of the cyst. ACKNOWLEDGMENTS The authors thank Dr Jean-Guillaume Grand for his help in the writing. REFERENCES 1. Hendrix D. 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