Epidemiology of canine glaucoma presented to University of Zurich from 1995 to 2009. Part 1: Congenital and primary glaucoma (4 and 123 cases)

Objective To investigate the epidemiology of canine congenital and primary glaucoma in the cases presented to the University of Zurich, Vetsuisse Faculty (UZH) from 1995 to 2009. Methods Information was obtained from the computer database of patients examined by members of the UZH Ophthalmology Service, between January 1995 and August 2009. Congenital and primary glaucoma was diagnosed based on the age of onset, the lack of evidence of any antecedent eye conditions, and/or the presence and severity of iridocorneal angle defects. The data was evaluated for breed, gender and age at presentation. Results A total of 5984 dogs presented to the UZH Ophthalmology service between 1995 and 2009. Four dogs of different breed were diagnosed with congenital glaucoma and 123 dogs were diagnosed with primary glaucoma. For the primary glaucomas the overall male to female ratio (M:F) was 1:1.41 and the age of onset ranged from 0.12 to 18.3 years with a mean of 7.3 ± 3.6 years. Data suggested a predisposition for primary glaucoma in the Siberian Husky, Magyar Vizsla and Newfoundland from 2004 to 2009. Conclusion The report presents the epidemiology of canine congenital and primary glaucomas presented to the UZH from 1995 to 2009. A previous suspicion of predisposition for primary glaucoma in the Newfoundland dog (n = 6) and the Magyar Vizsla breed (n = 8) was confirmed.     

Prevalence of the breed-related glaucomas in pure-bred dogs in North America

Objective To determine the prevalence of the breed‐related glaucomas in pure‐bred dogs presented to the veterinary medical teaching hospitals in North America that participate in the Veterinary Medical Data Base (VMDB). Materials and methods In this retrospective study, age of first diagnosis, breed, and gender data for all breeds of dogs were collected from the VMDB with the clinical diagnosis of primary glaucoma (glaucoma‐NOS) at 5–10 year intervals from 1964 to 2002. The prevalence for each breed (affected dogs compared to all dogs of each breed), any changes over the 38 years, and any gender differences for these glaucomas were determined. Results The prevalence of the primary breed‐related glaucomas has gradually increased from 0.29% (1964–1973); 0.46% (1974–1983); 0.76% (1984–1993); to 0.89% (1994–2002). Breeds that consistently featured among the highest 10 for glaucoma prevalence from four different periods (1964 to 2002) included American Cocker Spaniel, Basset Hound, Wire Fox Terrier, and Boston Terrier. During the last observation period (1994–2002), 22 different breeds had 1% or higher prevalence of the glaucomas. The highest prevalence of glaucomas in 1994–2002 by breed included: American Cocker Spaniel (5.52%); Basset Hound (5.44%); Chow Chow (4.70%); Shar‐Pei (4.40%); Boston Terrier (2.88%); Wire Fox Terrier (2.28%); Norwegian ElkHound (1.98%); Siberian Husky (1.88%); Cairn Terrier (1.82%); and Miniature Poodle (1.68%). A predominance of females with glaucoma occurred in the American Cocker Spaniel, Basset Hound, Cairn Terrier, Chow Chow, English Cocker Spaniel, Samoyed, and perhaps the Siberian Husky, and a predominance of males in the Australian Cattle dog and St Bernard. Age affected the time for first presentation of the glaucomas in the pure‐bred dog. In the majority of breeds the glaucomas were presented for initial diagnosis in dogs between 4 and 10 years of age. Conclusion Breed‐related glaucomas in pure‐bred dogs are frequently presented to the veterinary medical teaching hospitals in North America. The prevalence of the breed‐related glaucomas in the dog appears similar to humans, and in some breeds exceeds that in humans. In many breeds the high prevalence of the glaucomas suggests a genetic basis.     

Secondary glaucomas in the dog in North America

OBJECTIVE: To determine the prevalence of secondary glaucomas in dogs associated with cataract formation, lens luxation or displacement, cataract surgery, uveitis, hyphema and intraocular neoplasia. METHODS: Information was obtained from the Veterinary Medical Data Base (VMDB) from all veterinary medical teaching hospitals in North America from March 1964 to March 2003. Secondary glaucomas were diagnosed at the same examination or after the primary diagnosis was made, and included those associated with cataract formation, lens luxation, cataract surgery, uveitis of unknown cause, hyphema of unknown cause, and intraocular neoplasia. The data were evaluated by decade, breed, gender and age of presentation. RESULTS: A total of 1 592 831 dogs were presented, and 9695 canine secondary glaucomas. Secondary glaucoma associated with cataract formation represented 81% of all the canine secondary glaucomas. Breeds (n = 7890 dogs) predisposed to secondary glaucoma and cataracts had an overall prevalence of 0.5%, but nearly 20% of all the cataractous dogs developed secondary glaucoma in at least one eye. For the years 1994-2003, these breeds included the American Cocker Spaniel; Boston Terrier; Toy, Miniature and Standard Poodle; English Springer Spaniel; Bichon Frise; and Labrador Retriever. The other forms of secondary glaucoma occurred less frequently, and included those glaucomas with lens luxation or displacement (779 dogs; 12.0%), postcataract surgery (528 dogs; 5.1%), with uveitis from unknown cause (399 dogs; 7.1%), with hyphema from unknown cause (117 dogs; 7.3%), and with intraocular neoplasia (19 dogs; 3.5%). The risk of the secondary glaucomas from 1984 to 2002 was highest after the intracapsular lens extraction (ICLE), less in the extracapsular technique (ECLE), and lowest for the phacoemulsification/phacofragmentation method. CONCLUSION: Prevalence of the canine secondary glaucomas ranges from 0.25% (1964-1973), 0.46% (1974-1983), 0.79% (1984-1993), to 0.80% (1994-2003) and are as frequent as the primary or breed-related glaucomas during these same time periods.     

Evaluation of risk factors for development of secondary glaucoma in dogs: 156 cases (1999-2004)

OBJECTIVE: To determine the immediately antecedent cause of secondary glaucoma and the prevalence of secondary glaucoma with anterior uveitis or lens dislocation in dogs. DESIGN: Retrospective case series. ANIMALS: 156 dogs with secondary glaucoma. PROCEDURES: Cause of glaucoma was determined from records. Breed, age, sex, and neuter status of all dogs with secondary glaucoma were compared with the general hospital population. The prevalence of secondary glaucoma in dogs with a primary diagnosis of lens dislocation or anterior uveitis during the same period was determined. RESULTS: Secondary glaucoma was diagnosed in 156 of 2,257 (6.9%) dogs examined because of ophthalmic disease and was bilateral in 33 (21.2%) of those dogs. In 31 (94%) bilaterally affected dogs, the antecedent cause was the same in both eyes. Common causes of secondary glaucoma were non-surgical anterior uveitis (44.9%), anterior uveitis associated with prior phacoemulsification (15.8%), and lens dislocation (15.2%). Parson Russell Terriers, Poodles, Boston Terriers, Cocker Spaniels, Rhodesian Ridgebacks, and Australian Cattle Dogs had diagnoses of secondary glaucoma more often than expected, compared with the reference population. Age, sex, neuter status, and laterality were not associated with secondary glaucoma. The prevalence of secondary glaucoma in dogs with lens dislocation or uveitis was 15% or 17%, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Glaucoma develops secondary to many intraocular diseases, particularly uveitis and lens dislocation. Diagnosis of these diseases should prompt frequent monitoring of intraocular pressure, regardless of signalment.     

Characterization of Hepatoportal Microvascular Dysplasia in a Kindred of Cairn Terriers

Hepatoportal microvascular dysplasia (MVD), a congenital disorder of the hepatic vasculature, is described in a kindred of Cairn Terrier dogs. Cairn Terrier dogs (n = 165) were evaluated using the serum bile acid test. Affected dogs, identified by abnormal fasting or postprandial serum bile acid concentrations, were divided into 2 groups. Group 1 dogs (n = 147) were used for pedigree analysis. Group 2 dogs (n = 18) were characterized on the basis of history, physical examination, clinicopathologic studies, diagnostic imaging of the liver and portal circulation, and hepatic histopathology. Group 2 contained control dogs (n = 2), dogs with hepatoportal MVD (n = 11), and dogs with macroscopic portosystemic vascular anomalies (PVSA) (n = 5). With the exception of high serum bile acid concentrations, dogs with hepatoportal MVD were indistinguishable from control dogs on the basis of history, physical examination, clinicopathologic findings, survey abdominal radiography, abdominal ultrasound, or transcolonic scintigraphy. Contrast portography in dogs with MVD revealed abnormalities of terminal twigs of the portal vasculature with out large intrahepatic or extrahepatic shunting vessels. Histopathologic abnormalities in dogs with hepatoportal MVD were similar to those reported for dogs with PSVA. Pedigree analysis suggested an autosomal inheritance for MVD. Dogs with MVD had high serum bile acid concentrations, abnormal indocyanine green clearance, and hepatic pathology suggestive of PSVA, but they lacked characteristic clinical findings of PSVA. The clinical significance of MVD is unclear. Dogs with MVD were clinically normal when evaluated but long-term follow-up is not yet available. Dogs with hepatoportal MVD should be identified at an early age to avoid confusion in future diagnostic evaluations. J Vet Intern Med 1996:10:219–230. Copyright © 1996 by the American College of Veterinary Internal Medicine .     

Effects of risk factors and prophylactic treatment on primary glaucoma in the dog

Seventy dogs from 26 breeds were admitted with primary glaucoma between January 1979 and December 1983. Compared with mixed-breed dogs, 8 breeds were at higher risk (P less than 0.01) of developing glaucoma: Basset Hound, Beagle, Boston Terrier, Cocker Spaniel, Dalmatian, Miniature Poodle, Norwegian Elkhound, and Siberian Husky. Dogs between the ages of 5 and 10 years were at increased risk (P less than 0.001). There was no predisposition for either eye to be affected first (P greater than 0.55). Females were at twice the risk of males (P less than 0.01). Fourteen dogs had bilateral glaucoma. Among 46 dogs for which the number of months that the second eye remained normal was available, 24 were treated prophylactically and 22 were not treated or had treatment stopped. Prophylactic treatment significantly extended the interval between diagnosis in the first eye and development of glaucoma in the second eye for dogs in predisposed breeds (P less than 0.01). Prophylactic treatment did not make a difference when all breeds were considered (P greater than 0.19), nor did gender affect this interval (P greater than 0.37).     

Responses of atopic dogs to regional allergens: 268 cases (1981-1984)

Responses of atopic dogs to intradermal challenge with 60 allergens were determined and compared for 4 regions of the United States Twenty-seven allergens incited significantly higher responses in atopic dogs residing in northern Florida, when compared with dogs in Illinois; responses to 28 allergens were more significant in dogs residing in southern Florida vs Illinois. Only 1 allergen caused more responses in atopic dogs in northern Florida, compared with dogs in southern Florida. Females had a higher tendency to develop clinical signs of atopy. Dogs of the West Highland White Terrier, Cairn Terrier, English Setter, Irish Setter, Dalmatian, Lhasa Apso, Golden Retriever, and Labrador Retriever breeds were found to be predisposed to develop clinical signs of atopy. Dogs of the Poodle, Pug, German Shepherd Dog, Cocker Spaniel, Bulldog, Schnauzer, Doberman Pinscher breeds, of mixed breeding, and of terrier breeds other than the 2 aforementioned were not found to have a higher prevalence, when compared with the general hospital population. Of the atopic dogs evaluated in Florida, 79% had a significant response to flea antigen, compared with only 9% of atopic dogs evaluated in Illinois.     

Myocilin protein levels in the aqueous humor of the glaucomas in selected canine breeds

Objective To compare aqueous humor myocilin protein levels in dogs with the primary glaucomas to those with the secondary glaucomas, primary cataracts, and diabetic cataracts. Materials and methods Four groups were selected, based on diagnosis by the attending veterinary ophthalmologists and included: primary glaucoma (primary open‐angle glaucoma (POAG) and primary closed angle glaucoma (PCAG); n = 155); secondary glaucoma (n = 94); primary (presumed inherited) cataract (n = 142), and diabetic cataract (n = 83). A total of 474 samples (187 males, 263 females, 24 unreported) with average ages of 117 months for the males and 101 months for the females were analyzed. Myocilin protein was measured using the Coomassie staining and Western blot methods relative to a myocilin control. Results Differences were seen between nonglaucomatous (cataractous) and glaucomatous dogs with myocilin levels in glaucomatous eyes being many times higher than those in the cataractous dogs. Primary glaucomatous dogs were found to have an aqueous humor myocilin protein level of 17.30 ± 1.03 units. Secondary glaucomas had the highest level of myocilin in the aqueous humor with 19.27 ± 1.41 units. Diabetic cataractous dogs had the lowest levels of myocilin reported with 6.60 ± 0.88 (mean ± SEM) units. Normal (cataractous) dogs had a myocilin level in the aqueous humor of 8.05 ± 0.86 units. Conclusion Aqueous humor protein levels were elevated, relative to the myocilin control, in both the primary and secondary glaucoma groups compared to the cataract and diabetic cataract groups. Like in the Beagle POAG, aqueous humor myocilin protein levels are increased. Further studies are indicated to investigate the exact role of the aqueous humor myocilin protein in the genesis in increased IOP in these primary glaucomatous breeds.     

Incidence of canine glaucoma with goniodysplasia in Japan : a retrospective study

The incidence of primary and secondary glaucoma in dogs was investigated. A total of 1244 dogs received ophthalmologic examinations, including tonometry and gonioscopy. Goniophotographs were taken using a goniolens to evaluate the iridocorneal angle (ICA) as well as pectinate ligament (PL). The anterior width of the ciliary cleft and the total distance from the origin of the PL to the anterior corneal surface were measured from the goniophotographs. Glaucoma was diagnosed based on the cupping of the optic nerve head, clinical signs, ocular changes, and high IOP, and it was synchronized with gonioscopic grades to differentiate between primary and secondary glaucoma. We investigated 1244 dogs of 29 breeds, including the mixed breed; among these, glaucoma was diagnosed in 127 dogs (162 eyes). Of 162 eyes, primary glaucoma was diagnosed in 129 eyes and secondary glaucoma in 33 eyes. Shiba Inu dogs (42 dogs, 33%) showed the highest incidence of glaucoma, followed by Shih-Tzu (21 dogs, 16.5%). Furthermore, all the glaucomatous Shiba Inu dogs had primary glaucoma with abnormal ICA grades and dysplastic PLs. The findings of our study reveal that the Shiba Inu breed in Japan may have a hereditary predisposition to glaucoma.     

Inherited congenital extrahepatic portosystemic shunts in Cairn terriers

The pathogenesis of congenital portosystemic shunt (CPSS) in dogs still is incompletely understood. In Irish Wolfhounds and Yorkshire Terriers, CPSS is reported to be hereditary. The aim of this study was to investigate a possible genetic basis and the mode of inheritance of CPSS in Cairn Terriers. Between July 1990 and July 2001, 6-week-old pups of the Dutch Cairn Terrier population were screened by measuring venous ammonia concentrations and in the presence of hyperammonemia by ultrasonography, autopsy, portal vein angiography, or exploratory celiotomy. The same successfully operated female was used 3 times in test matings with an unrelated affected male, her unaffected sire, and an affected offspring. The prevalence of CPSS in the general Cairn Terrier population, the direct progeny of frequently used males, and the offspring of the test matings were tested for significant differences. In total, 6,367 Cairn Terriers were screened; 32 males and 26 females had CPSS. In 3 large family groups, significantly higher prevalences were found compared with the general population (P < .0001, P < .0001, and P < .044). The prevalence of CPSS in the offspring of the test matings was significantly higher (P < .002) than in the general population. No sex predisposition occurred among the affected dogs. The higher prevalence of CPSS in the test matings and the 3 family groups compared with the general population indicates that CPSS in Cairn Terriers is a genetic disease. The inheritance is autosomal and most likely polygenic or monogenic with variable expression.     

Development of glaucoma after phacoemulsification for removal of cataracts in dogs: 22 cases (1987-1997)

OBJECTIVE: To determine factors contributing to glaucoma after lens extraction via phacoemulsification in dogs. DESIGN: Retrospective study. ANIMALS: 22 dogs (29 eyes) with glaucoma and 21 dogs (30 eyes) without glaucoma after phacoemulsification. PROCEDURE: Medical record review. RESULTS: Eyes at increased risk for glaucoma included those of Boston Terriers, those with uveal or retinal abnormalities before surgery, and those with intraoperative intraocular hemorrhage. Significant differences between groups were not detected for incidence of preoperative lens-induced uveitis, presence of an intraocular lens, or frequency of an acute postoperative increase in intraocular pressure. Glaucoma developed (mean +/- SD) 12.8+/-14.1 months (median, 10 months; range, 0.25 to 55 months) after surgery. Eighteen of 29 (62%) eyes with potential for vision after onset of glaucoma retained vision for a mean of 16.5+/-12.8 months (median, 10.8 months; range, 1.5 to 37 months) after glaucoma was diagnosed. Most of these eyes still had vision at the conclusion of the study period. CONCLUSIONS AND CLINICAL RELEVANCE: Risk factors identified by this study will aid in preoperative counseling of clients and refining selection criteria for candidates for phacoemulsification. Careful follow-up for the remainder of the dog's life after surgery may improve long-term success rates by permitting early intervention before intraocular pressure increases substantially and vision is irreversibly lost. Surgery for cataracts may still be worthwhile in dogs with increased risk of glaucoma, especially if elderly, because of the lengthy period to onset of glaucoma after surgery and the beneficial effects of treatment after glaucoma develops.     

Abnormal ocular pigment deposition and glaucoma in the dog

The combined occurrence of ocular pigment deposition and glaucoma has been described in Cairn Terriers. Recently, this condition was also observed in two other breeds: the Boxer (two cases) and the Labrador Retriever (one case). Six dogs were referred to the Ophthalmology section of the Department of Clinical Sciences of Companion Animals and to a private referral clinic because of glaucoma or blindness in one or both eyes. In five cases ophthalmic examination showed pigment depositions in the sclera around the entire circumference of the perilimbal zone. Eight enucleated eyes (four eyes of two Cairn Terriers, three eyes of two Boxers and one eye of a Labrador Retriever) were examined microscopically. All eyes showed the same findings: an extensive infiltration of large melanin-containing cells with an eccentric nucleus, located in the iris, ciliary body, retina, choroids and sclera. Transmission electron microscopy of two of the examined eyes revealed that the morphology of most of these cells was consistent with melanophages. While reports in the veterinary literature concerning this condition are limited the cells concerned have been described to be melanocytes. Further research is needed to conclusively identify the cell type. As described in the present report, the histologic and transmission electron microscopic findings suggest a different etiology of the ocular pigment deposition and glaucoma compared with the pigment dispersal syndrome in humans.     

Use of cyclocryotherapy in management of glaucoma in dogs

In 5 cases of glaucoma (2 from trauma, 2 from narrowed drainage angles, 1 secondary to lens extraction), cyclocryotherapy was used to control intraocular pressure. In all cases the intraocular pressure decreased, with the usual result being a cosmetic and painless but blind eye.     

The future of canine glaucoma therapy

Canine glaucoma is a group of disorders that are generally associated with increased intraocular pressure (IOP) resulting in a characteristic optic neuropathy. Glaucoma is a leading cause of irreversible vision loss in dogs and may be either primary or secondary. Despite the growing spectrum of medical and surgical therapies, there is no cure, and many affected dogs go blind. Often eyes are enucleated because of painfully high, uncontrollable IOP. While progressive vision loss due to primary glaucoma is considered preventable in some humans, this is mostly not true for dogs. There is an urgent need for more effective, affordable treatment options. Because newly developed glaucoma medications are emerging at a very slow rate and may not be effective in dogs, work toward improving surgical options may be the most rewarding approach in the near term. This Viewpoint Article summarizes the discussions and recommended research strategies of both a Think Tank and a Consortium focused on the development of more effective therapies for canine glaucoma; both were organized and funded by the American College of Veterinary Ophthalmologists Vision for Animals Foundation (ACVO‐VAF). The recommendations consist of (a) better understanding of disease mechanisms, (b) early glaucoma diagnosis and disease staging, (c) optimization of IOP‐lowering medical treatment, (d) new surgical therapies to control IOP, and (e) novel treatment strategies, such as gene and stem cell therapies, neuroprotection, and neuroregeneration. In order to address these needs, increases in research funding specifically focused on canine glaucoma are necessary.     

Lichtmikroskopische Untersuchungen über das Glaukom der Katze

In the paper presented, the histological findings in four cats with glaucoma are reported by means of HE-stained paraffin embedded sections. To each case a clinical anamnesis is given. The authors describe primary glaucomas as well as secondary glaucomas of different aetiology. A dysplastic pectinate ligament can be identified for the first time in a cat. Clinical and histological findings are discussed and compared to the findings in dogs.     

Multiple ciliary body cysts and secondary glaucoma in the Great Dane: a report of nine cases

Between 1989 and 1995 nine Great Danes were presented to the small animal clinic of the University of Zurich Teaching Hospital with glaucoma and multiple cysts in the anterior and posterior chamber. In four of the nine dogs cysts were present in both eyes; however, bilateral glaucoma was seen in one case only. Mean intraocular pressure (IOP) at initial presentation was 42 mmHg measured by applanation tonometry. With the exception of one dog, all animals were treated medically for a minimum of 13 days. Two animals were subsequently lost to follow up. Two dogs underwent evisceration with implantation of a silicone prosthesis. The glaucomatous globe was enucleated in three dogs. One owner declined surgery and the dog remained buphthalmic with a poorly controlled IOP. One animal remained visual after trans-scleral diode laser cyclophotocoagulation. Histopathology of the three enucleated globes showed multiple cysts originating from the ciliary body epithelium. The mechanism of IOP elevation is probably by anterior displacement of the iris with narrowing of the angle and collapse of the ciliary cleft. A delicate pre-iridal fibrovascular membrane was also seen in each case, which could have also contributed to the elevation of IOP. The high odds ratio of 2.23 (CI 95% 1.14, 3.99) for glaucoma and 37.01 (CI 95% 16.42, 77.81) for ciliary body cysts suggests they are both inherited in this breed. Pedigree analysis of the affected dogs failed to definitely reveal the mode of inheritance.     

Comparative Doppler imaging of the ophthalmic vasculature in normal Beagles and Beagles with inherited primary open-angle glaucoma

The objective of this study was to compare orbital and ocular vasculature velocity, measured by Doppler imaging, in normal Beagles and Beagles with inherited primary open-angle glaucoma. Eight normal Beagles and 13 Beagles with different stages of primary open-angle glaucoma were evaluated twice with a 2–4-week period between measurements. Doppler imaging was performed with the dogs anesthetized, and the Doppler transducer applied directly on the corneal surface. The majority of the orbital vasculature (external ethmoidal artery; internal ophthalmic artery and vein; and external ophthalmic artery and vein) and ocular blood vessels (anterior ciliary artery and veins; long posterior ciliary arteries; short posterior ciliary arteries; primary retinal arteries; and the vortex veins) were identified and Doppler blood velocity parameters were determined. The glaucomatous dogs demonstrated significant differences in the Doppler velocity parameters of several orbital vessels (external ethmoidal, external ophthalmic, and internal ophthalmic arteries), and several ocular vessels (anterior ciliary, short posterior ciliary, and long posterior ciliary arteries). These differences included decreased blood velocities, and increased pulsatility and resistive indexes. The Doppler blood flow velocities of the primary retinal arteries were unchanged between the normal and glaucomatous dogs. In the glaucomatous dogs, the Doppler imaging suggests increased vascular resistance downstream in both the orbital and ocular vasculature. These blood velocity parameter changes may be primary or secondary, and may offer therapeutic opportunities to increase perfusion, prolong the retina and optic nerve head function, and maintain vision in the canine glaucomas.     

Combined cycloablation and gonioimplantation for treatment of glaucoma in dogs: 18 cases (1992-1998)

OBJECTIVE: To evaluate a combined cycloablative and gonioimplantation technique for treatment of glaucoma in dogs. DESIGN: Retrospective study. ANIMALS: 18 adult dogs with glaucoma. PROCEDURE: Medical records of dogs that received a valved gonioimplant and a cyclodestructive procedure (cyclocryoablation or diode laser cyclophotocoagulation) during a 6-year period were reviewed. Retention of vision and intraocular pressure control were assessed, as well as number and nature of complications. RESULTS: 19 eyes of 18 dogs received a valved gonioimplant and either cyclocryoablation (n = 12) or diode laser cyclophotocoagulation (7). At > or = 1 year after surgery, 11 of 19 eyes had vision and 14 of 19 eyes had intraocular pressure < 25 mm Hg. Two dogs (2 eyes) were lost to follow-up 3 and 6 months after surgery. Despite the alternative route for aqueous humor flow created by the gonioimplant, 7 eyes had increased intraocular pressure (27 to 61 mm Hg) < 24 hours after surgery. Other complications included excessive intraocular fibrin, focal retinal detachment, corneal ulcer, retinal hemorrhage, cataract, and implant migration. CONCLUSIONS AND CLINICAL RELEVANCE: Combined cycloablation and gonioimplantation appears to be a promising technique for retention of vision and control of intraocular pressure in dogs with glaucoma.     

Cullen frontal sinus valved glaucoma shunt: preliminary findings in dogs with primary glaucoma

PURPOSE: To evaluate the efficacy of a novel, professionally manufactured, frontal sinus valved glaucoma shunt in maintaining normal intraocular pressure (IOP) and vision in dogs with primary glaucoma. METHODS: Three eyes of three dogs diagnosed with primary glaucoma were included in this prospective clinical study. A Cullen frontal sinus valved glaucoma shunt was implanted into each glaucomatous globe. Dogs were treated postoperatively with topical neomycin/polymyxin B/0.1% dexamethasone and 0.03% flurbiprofen every 6 h tapered over 8-12 weeks, and meloxicam at 0.1 mg/kg orally every 24 h for 7-10 days. IOP, intracameral shunt position and apparent patency, and vision were assessed twice daily for up to 4 (n= 3 eyes) and 10 (n= 2 eyes) days postoperatively, and then at re-examination periods of up to 36 weeks (n= 1 eye). Postoperative complications were recorded and documented photographically. RESULTS: Normal IOP was maintained in all shunted globes (range 10-29 mmHg; mean = 16.7 mmHg at 24 h; IOP = 23 mmHg at 36 weeks) postoperatively for 2 days (3/3 eyes), 8 weeks (2/2 eyes), and 36 weeks (1/1 eye) without additional antiglaucoma therapies. Photopic vision and shunt position and patency were maintained in all shunted globes for all follow-up periods. Postoperative complications included mild aqueous flare and fibrin (n= 3 eyes for 3-10 days postoperatively); intracameral shunt occlusion with fibrin (n= 1 eye at days 2 and 4); partial anterior chamber tube extrusion (n= 1 eye at day 4), and focal corneal edema (n= 1 eye at 18 weeks). Tissue plasminogen activator injected intracamerally through the silicone tube near the frontal sinus effectively resolved the fibrinous shunt occlusion. CONCLUSIONS: The Cullen frontal sinus valved glaucoma shunt shows promise for the management of canine primary glaucoma.     

Light-microscopy evaluation of zonular fiber morphology in dogs with glaucoma: secondary to lens displacement

Lens displacement resulting in secondary glaucoma is common in terrier breeds. This study was carried out to evaluate whether light microscopy was useful in detecting abnormal patterns in zonular fiber protein. Eyes from 63 dogs with glaucoma secondary to lens displacement were evaluated for the presence of abnormal zonular fiber morphology using the following stains: hematoxylin and eosin, periodic acid Schiff (PAS), Masson's trichrome and Verhoeff's elastin stains. Two distinct forms of abnormal zonular fiber morphology were recognized and designated as zonular fiber dysplasia (ZFD) and zonular fiber collagenization (ZFC). ZFD protein morphology was characterized by being tightly adherent to the nonpigmented ciliary body epithelium, exhibiting a distinct lamellar and cross-hatched pattern and staining strongly positive with PAS and trichrome stains, and staining negative with elastin stains. ZFD was predominant in terrier breeds (18 of 29) and Shar-Pei dogs (4 of 29). ZFC abnormality was characterized by excessive zonular fiber that was not tightly adherent to the ciliary body epithelium and staining positive with PAS, trichrome (blue for collagen) and elastin stains. Only 7 of 19 dogs with ZFC changes were terrier breeds, and there was no pattern in the breeds affected. Fifteen of the 63 dogs used in the study had normal appearing zonular fibers. The staining pattern in these dogs matched normal controls by staining positive with PAS and Verhoeff's elastin stains and had only minimal positive staining with Masson's trichrome stain. Results suggest that light microscopy is useful in detecting breed-related changes in zonular fiber morphology in cases of glaucoma secondary to lens displacement. These changes may correlate with the presence of abnormal zonular fiber proteins and might be important in the pathogenesis of primary lens displacement in terrier and Shar-Pei dogs.