A review of the pharmacology of carbonic anhydrase inhibitors for the treatment of glaucoma in dogs and cats

Glaucoma is a heterogeneous group of disorders usually associated with elevated intraocular pressure (IOP), leading to optic nerve damage, retinal ganglion cell death and irreversible vision loss. Therefore, medications that lower IOP are the mainstay of glaucoma therapy. Carbonic anhydrase inhibitors (CAIs) are some of the principal drugs used in the management of canine and feline glaucoma. This paper summarises current knowledge of the mechanism of action of these agents and their effect on IOP in dogs and cats. It also discusses potential harmful side effects of CAIs and presents current opinions about their role and place in the medical management of glaucoma in small animals.     

Surgical procedures for glaucoma: what the general practitioner needs to know

Glaucoma can be treated by medical and surgical options. Most ophthalmologists believe that patients with glaucoma are best treated with surgery. Early recognition of clinical signs and selection of the most effective type of surgery depending on the stage of glaucoma and the underlying cause are important factors in glaucoma surgery. Several surgical procedures exist for dogs with primary glaucoma, which may include a cyclodestructive technique or an aqueous outflow bypass procedure or a combination of both procedures. Salvage procedures such as enucleation, evisceration with an intrascleral prosthesis, or chemical intravitreal injection may be advised for chronically blind eyes with no hope of vision. Client compliance and expectations, therapeutic goals, status of vision (visual versus blind), financial constraints, surgical expertise, and underlying systemic disorders should be considered in the selection of the most appropriate surgical option for each patient.     

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.     

Pharmacology of topical prostaglandin F2α analogs and their place in the treatment of glaucoma in small animals

A distinguishing feature of the most common types of glaucoma is an increased intra‐ocular pressure (IOP), which has a damaging effect on optic nerve axons, leading to the progressive loss of retinal ganglion cells. Therefore, IOP‐lowering medications are the mainstay of glaucoma therapy. Topical prostaglandin F₂α analogs (PGAs) are a relatively new class of ocular hypotensive drugs, which have made a huge impact on the treatment of glaucoma in dogs. This study summarizes the current state of knowledge on the mechanism of action of these agents and their effect on IOP in dogs and cats. It also discusses potential harmful side effects of PGAs and presents contemporary opinions about their role and place in the medical management of glaucoma in small animals.     

The effect of 0.12% unoprostone isopropyl (rescula) on intraocular pressure in normotensive dogs

Rescula (0.12% unoprostone isopropyl) is the first docosanoid compound approved for treatment of glaucoma in humans. It is commercially available in Japan, and is undergoing clinical testing elsewhere. The aim of this study was to evaluate the effect of Rescula on intraocular pressure (IOP) in normotensive dogs. After establishing a baseline diurnal IOP curve, six dogs were unilaterally treated with Rescula while the contralateral eye was treated with a placebo. Applanation tonometry was performed in both eyes, and pupil size was evaluated, 30 min after treatment, and at 1-hr intervals for the next 9 hr. Rescula caused a significant (p=0.014) and long-lasting decrease in IOP, from 20.49+/-2.02 mm Hg in control eyes to 15.49+/-0.69 mm Hg in treated eyes. These results suggest that Rescula is potentially efficacious in treatment of canine glaucoma.     

Diagnosis and treatment of glaucoma in client-owned rabbits (Oryctolagus cuniculus): 16 eyes from 11 rabbits (2008–2019)

BackgroundAlthough rabbits are commonly used as laboratory models for human glaucoma, management of this disease in pet rabbits has received little attention in the current literature. Spontaneous congenital glaucoma was initially described in New Zealand Whites as an autosomal recessive trait manifesting early in life. Glaucoma may also develop secondary to cataracts, uveitis, or other ocular pathologies. Findings associated with glaucoma in rabbits include elevated intraocular pressure (IOP), corneal edema, loss of vision, optic nerve head cupping, and progressive buphthalmia. Topical medications, intravitreal gentamicin injections, and various surgical techniques have been used to manage glaucoma in rabbits. This case series details the presentation, diagnosis, treatment, and clinical progression of glaucoma in rabbits at Cummings Veterinary Medical Center at Tufts University and VCA South Shore (Weymouth) Animal Hospital from 2008-2019.MethodsThe records of Cummings Veterinary Medical Center at Tufts University and VCA South Shore (Weymouth) Animal Hospital were retrospectively reviewed to identify records of rabbits diagnosed with glaucoma by a board-certified veterinary ophthalmologist or ophthalmology resident between 2008-2019.ResultsGlaucoma was diagnosed in 16 eyes from 11 rabbits. Median IOP at diagnosis was 39 mmHg (26-55 mmHg) with various clinical signs at presentation including vision loss (11 rabbits, 16 eyes), buphthalmia (8 rabbits, 11 eyes), corneal edema (4 rabbits, 5 eyes), and optic nerve head cupping (5 rabbits, 6 eyes). Other ocular examination findings included cataracts (5 rabbits, 8 eyes) and uveitis (4 rabbits, 8 eyes). Two rabbits were seropositive for Encephalitozoon cuniculi. All eyes were initially treated with topical medications, with 10 eyes from 7 rabbits refractory to initial medical management. Two rabbits (3 eyes) showed progressive reduction in IOPs with long-term continuing topical therapy. Two rabbits (2 eyes) underwent unilateral enucleation and 3 rabbits (5 eyes) received intravitreal gentamicin injections.ConclusionsEtiology of glaucoma in rabbits is likely more varied than previously thought, as many of the cases described were not consistent with primary congenital glaucoma. Topical treatments were effective in many rabbits. In those refractory to medical management, enucleation or intravitreal gentamicin injection were successful in decreasing IOP as second-line therapy when performed.     

Intracapsular lensectomy and sulcus intraocular lens fixation in dogs with primary lens luxation or subluxation

Objective  To evaluate the postoperative results of lensectomy and sulcus intraocular lens fixation (SIOLF) via an ab interno approach in dogs with progressive lens subluxation or early luxation.
Study design  Retrospective study.
Animals studied  Twenty eyes from 19 dogs presented to the Animal Eye Clinic for lens luxation or subluxation between 1999 and 2006.
Methods  Medical records were reviewed to evaluate preoperative lens position, vision status, intraocular pressure (IOP), and whether surgery was performed on an emergent or elective nature. Lensectomy and SIOLF were performed and postoperative status including vision, glaucoma, and retinal detachment was assessed.
Results  Average age was 8.6 years (range 4–14 years) and 55% (11/20) were terriers. Patients were followed a mean of 29.2 months (range 1–92 months) after surgery. Retinal detachment or secondary glaucoma was observed in 1 of 20 (5%) and 5 of 20 (20%) eyes, respectively, with 1 of 20 (5%) exhibiting both. Mean preoperative IOP was 16 mmHg and preoperative lens position was equally divided between luxated and subluxated lenses. Surgery was performed more frequently as an elective procedure (18/20; 90%) due to normalized IOP vs. an emergency procedure (2/20; 10%). Vision was retained in 70% (14/20) of eyes with a mean time to vision loss of 41 months in the remaining eyes due to glaucoma, retinal detachment, or retinal degeneration.
Conclusions  Complications of glaucoma and retinal detachment after SIOLF in this study were less when compared with previously reported incidence rates in the literature for lensectomy alone which may reflect improved patient selection.     

The Treatment of Acute Glaucoma in Dogs and Cats

Objective: Glaucoma is an optic nerve disease that may result in rapid loss of vision. Early detection of acute glaucoma and aggressive treatment is important to preserve vision. Continued treatment is indicated in chronic glaucoma to alleviate discomfort associated with chronic elevated intraocular pressure.
Etiology: In primary glaucoma, an abnormal iridocorneal angle results in obstruction to outflow of aqueous humor. In secondary glaucoma, an otherwise normal iridocorneal angle is obstructed by abnormalities such as a luxated lens, neovascular membranes or inflammatory material.
Diagnosis: The diagnosis is made by a combination of clinical signs such as corneal edema, mydriasis, decreased vision, episcleral hyperemia, and confirmed by measuring an elevation in intraocular pressure. Complete ophthalmic examination, knowledge of breed predisposition to various ocular diseases and gonioscopy will aid in distinguishing between primary and secondary glaucoma
Therapy: Aggressive medical management is important in acute glaucoma. Surgical procedures are often indicated after initial emergency medical treatment of acute glaucoma. Chronic, painful blind eyes are best treated with one of various surgical procedures.
Prognosis: The prognosis for maintaining vision or regaining temporarily lost vision in acute glaucoma is related to numerous factors including time between onset of clinical signs and appropriate treatment, etiology of the glaucoma, initial response to therapy and client compliance.     

Soft tissue sarcoma in the dog – Part 2: surgical margins,controversies and a comparative review

Soft tissue sarcoma constitutes a heterogeneous group of mesenchymal tumours. Although they are common in the dog, many uncertainties surround the best options for clinical management. Despite recent improvements in outcome, approximately one in five patients may still die as a result of their disease. There is some evidence that wide surgical excision may not be required for every soft tissue sarcoma but, conversely, complacency in treatment may adversely affect outcomes for patients with aggressive disease. The purpose of this review is to examine the issues affecting the management of canine soft tissue sarcoma, and to evaluate the human literature for lessons that may guide future treatment directions for dogs. Comparative lessons from human soft tissue sarcoma that may be important for the canine patient in the future include (1) understanding the oncogenic potential of the pseudocapsule to better predict tumour behaviour and optimal surgical margins, (2) recognising the importance of planned multi‐modality therapy for improving tumour control, (3) considering a role for compartmental resection strategies and (4) improving the accuracy of pretreatment analysis of the tumour to better predict behaviour and optimal treatment options.     

Comparison of the use of new handheld tonometers and established applanation tonometers in dogs

OBJECTIVE: To examine the practical aspects, accuracy, and reproducibility of 2 new automatic handheld tonometers in dogs and compare them with results for 2 established applanation tonometers. ANIMALS: 15 freshly enucleated canine eyes for manometric evaluation and 20 conscious research dogs, 20 client-owned dogs, and 12 dogs with acute glaucoma for clinical tonometry. PROCEDURE: Calibration curves were determined for all 4 tonometers on 15 enucleated canine eyes. Intraocular pressure (IOP) was measured with each tonometer consecutively in conscious dogs, with the MacKay-Marg applanation tonometer as the reference device. Measurements were repeated in 20 sedated dogs. An induction-impact tonometer was evaluated clinically on dogs with acute glaucoma. Additionally, measurements obtained by an experienced and an inexperienced examiner and with or without use of topical anesthesia were compared. RESULTS: The portable pneumatonometer was cumbersome and time-consuming. Compared with results for the reference applanation tonometer, and confirmed by manometry, the portable pneumatonometer increasingly underestimated actual IOP values with increasing IOP. The induction-impact tonometer provided accurate and reproducible measurement values. There was a significant strong correlation between the IOP values obtained by the 2 examiners (r2, 0.82) and also with or without topical anesthesia (r2, 0.86). In dogs with glaucoma, the fitted line comparing values for the reference applanation tonometer and induction-impact tonometer closely resembled an ideal 1:1 relationship. CONCLUSIONS AND CLINICAL RELEVANCE: Use of the portable pneumatonometer in dogs appears to have disadvantages. The induction-impact tonometer appears to provide a promising alternative to the use of applanation tonometers in dogs.     

Myasthenia gravis in dogs with an emphasis on treatment and critical care management

Objective – To review the human and veterinary literature on the pathophysiology of myasthenia gravis (MG) and describe treatment options for clinical use in people and animals. Data Sources – Human and veterinary clinical reports, studies and reviews, textbooks, and recent research findings in MG from 1996 present, with a focus on treatment and patient management. Human Data Synthesis – MG is a well‐described condition in people with new research and treatment options available. Many of the newest therapeutic options available in veterinary medicine for MG are based on current strategies used in people with this condition. Seronegative MG is well described in people and provides insight to clinical cases encountered in veterinary medicine when the index of suspicion is high though serologic tests are negative. Veterinary Data Synthesis – Previous studies in veterinary medicine focused on the use of acetylcholinesterase inhibitors as the main form of treatment in canine MG. Recent studies, mainly case series and case reports, emphasize the use of immunomodulatory treatments as an alternative for long‐term treatment. However, there are no randomized, controlled studies on treatment with immunomodulatory therapy for MG in dogs available to assess the efficacy of this treatment strategy. Conclusions – Although early recognition of clinical signs is most important in the outcome of patients with MG, further understanding the pathophysiology of MG may lead to earlier diagnosis and novel treatment strategies. The discovery of additional autoantibodies against striated muscle proteins in dogs, should enhance our understanding of diseases affecting the neuromuscular junction. In addition, clinical data for canine MG could be applied to other autoimmune disorders.     

Combined transscleral diode laser cyclophotocoagulation and Ahmed gonioimplantation in dogs with primary glaucoma: 51 cases (1996-2004)

OBJECTIVE: To evaluate the combined diode laser cycloablation procedure and adjunctive Ahmed gonioimplant use in dogs with primary glaucoma. DESIGN: Retrospective study. ANIMALS: 48 dogs, 51 eyes with primary glaucoma. PROCEDURE: Medical records from two large private clinical ophthalmology services were reviewed. Signalment, duration of glaucoma, gonioscopic evaluation, laser power and duration settings, immediate postoperative and final intraocular pressure and visual results, short and long-term visual outcome, and surgical complications were recorded. RESULTS: The age range of affected dogs was 3.0-14.0 years, with a mean age of 7.5 +/- 2.6 years. Eleven pure breeds were represented, with the most common being the American Cocker Spaniel. The sex distribution was 22 neutered males, 1 intact male, 23 spayed females, and 2 intact female dogs. The right eye was affected in 33 cases, and the left eye in 18 cases. The average total joules, which was administered with the diode laser, was 109.6 +/- 23.6 J. Immediate surgical complications included fibrin formation in the anterior chamber (15), corneal ulcers (4), hyphema (7), and focal retinal detachment (1). Long-term complications included cataract formation (8 total, 2 of which were significant, vision-threatening), elevated intraocular pressure (IOP) (6), unstable gonioimplant (1), and glaucoma recurrence (14). Additional surgeries performed on the eyes over the course of study included: intrascleral prosthesis (4), enucleation (1), resection of fibrotic scar tissue (5), and repeat laser cycloablation (8). The dogs were examined for a mean follow-up time of 17.6 months (range: 2-83 months postoperatively). Twenty-nine cases were followed greater than one year. Vision was maintained in 42/51 eyes (82%) in the immediate short-term of this study. In all cases included in the study, good control of IOP was achieved in 39/51 (76%) of eyes, and IOP was poor or uncontrolled in 12/51 (24%) of eyes. Twenty out of 41 eyes (49%) maintained fair to excellent vision six months after surgery. Twelve months postoperative observations demonstrated that 12/29 (41%) of the eyes were still visual. CONCLUSIONS: In primary glaucoma, the combined procedure of laser diode cyclophotocoagulation and Ahmed valve implant was associated with return or maintenance of vision in 42/51 eyes (82%) in the immediate short-term of this study, and a long-term IOP control in 39/51 (76%) of the cases, with 12/29 eyes (41%) visual after 12 months.     

The use of transscleral cyclophotocoagulation with a diode laser for the treatment of glaucoma occurring post intracapsular extraction of displaced lenses: a retrospective study of 15 dogs (1995-2000)

The objective of this retrospective study was to evaluate transscleral cyclophotocoagulation (TSCP) using a diode laser for treating aphakic glaucoma that developed after intracapsular lens extraction (ICLE) had been performed for displaced lenses. Records of 15 dogs (21 eyes) were reviewed. The intraocular pressure (IOP) and the presence of vision were recorded at the time of ICLE and TSCP and at 1, 3, 6-9, 12 and 24 months post TSCP. The glaucoma was considered controlled if the IOP was less than 25 mmHg. The results indicated that the effectiveness of TSCP using a diode laser for treating aphakic glaucoma was of a short-term duration (1-3 months), with three patients needing repeat TSPC. In addition, adjunctive antiglaucoma medications were often required to maintain an adequately controlled IOP. Over the 24-month period the number of dogs requiring intrascleral prosthesis, intraocular gentamicin or enucleation, or that were lost to follow-up, increased.     

Use of a Baerveldt gonioimplant for secondary glaucoma in a horse

This case report describes the surgical placement of a Baerveldt glaucoma shunt in the right eye of a 14‐year‐old Arabian gelding. The glaucomatous right eye was refractory to aggressive medical and repeated surgical therapies yet maintained functional vision. Despite the need for intensive post operative management and continued daily topical therapy, shunt placement surgery was successful at maintaining normotension and vision for a period of 402 days. This is the first report of long‐term successful glaucoma filtration surgery in this species. Further studies are warranted to evaluate long‐term success of glaucoma shunt placement in equine glaucoma cases.     

A promising surgical approach to equine glaucoma

The preceding case report by Wilson et al. (2015) describes the surgical placement of a Baerveldt glaucoma shunt in a glaucomatous equine eye that had been refractory to aggressive medical and repeated surgical therapies yet maintained functional vision. Shunt placement surgery successfully maintained vision and intraocular pressure in the normal range in the affected eye. This is the first report of long‐term successful glaucoma filtration surgery in a horse. Glaucoma shunt placement shows promise for maintaining vision and comfort in equine eyes affected with glaucoma. There is much to be learned in terms of the most appropriate implant type for the equine eye, the risk of complications such as ocular hypotony or tube fibrosis, and the utility of combination therapy with transcleral cyclophotocoagulation and implant placement, but with the report of one case in which gonioimplant placement has been associated with intraocular pressure control for over one year, further investigations appear warranted. This case provides a glimmer of hope for long‐term treatment of a painful, blinding disease that has traditionally carried a poor prognosis in horses.     

Effects of topical application of a 2% solution of dorzolamide on intraocular pressure and aqueous humor flow rate in clinically normal dogs

OBJECTIVE: To evaluate effects of topical application of a 2% solution of dorzolamide on intraocular pressure (IOP) and aqueous humor flow rate in clinically normal dogs. ANIMALS: 15 Beagles. PROCEDURE: The IOP was measured in both eyes of all dogs for 3 days to determine baseline values. In a single-dose study, 50 microl of dorzolamide or control solution was applied in both eyes at 7:00 AM, and IOP was measured 7 times/d. In a multiple-dose study, dorzolamide or control solution was applied to both eyes 3 times/d for 6 days, and IOP was measured 4 times/d during treatment and for 5 days after cessation of treatment. Aqueous humor flow rate was measured for all dogs fluorophotometrically prior to treatment and during the multiple-dose study. RESULTS: In the single-dose study, dorzolamide significantly decreased IOP from 30 minutes to 6 hours after treatment. Mean decrease in IOP during this time span was 3.1 mm Hg (18.2%). Maximal decrease was detected 6 hours after treatment (3.8 mm Hg, 22.5%). In the multiple-dose study, dorzolamide decreased IOP at all time points, and maximal decrease was detected 3 hours after treatment (4.1 mm Hg, 24.3%). Mean aqueous humor flow rate decreased from 5.9 to 3.4 microl/min (43%) after treatment in the dorzolamide group. CONCLUSIONS AND CLINICAL RELEVANCE: Topical application of a 2% solution of dorzolamide significantly decreases IOP and aqueous humor flow rate in clinically normal dogs. Therefore, topical administration of dorzolamide should be considered for the medical management of dogs with glaucoma.     

Light at the end of the tunnel? Advances in the understanding and treatment of glaucoma and inherited retinal degeneration

Glaucoma and inherited retinal degeneration/dystrophy are leading causes of blindness in veterinary patients. Currently, there is no treatment for the loss of vision that characterizes both groups of diseases. However, this reality may soon change as recent advances in understanding of the disease processes allow researchers to develop new therapies aimed at preventing blindness and restoring vision to blind patients. Elucidating the molecular mechanisms of retinal ganglion cell death in glaucoma patients has led to the development of neuroprotective drugs which protect retinal cells and their function from the disastrous effects of elevated pressure. Identification of the genetic mutation responsible for inherited degenerations and dystrophies of the outer retina has enabled researchers using gene therapy to restore vision to blind dogs. Other patients may benefit from retinal transplantation, stem cell therapy, neuroprotective drugs, nutritional supplementation and even retinal prostheses. It is possible that soon it will be possible to restore sight to some blind patients.     

Uveitic glaucoma in the horse

Glaucoma is a serious complication of anterior uveitis that can result in significant ocular discomfort and loss of vision. As glaucoma is insidious and mostly asymptomatic until late in the course of disease, it is often undiagnosed. Equine recurrent uveitis is the most common underlying disorder: it is a disease of high prevalence, characterised by recurrent‐remitting episodes of ocular inflammation. Here, the inflammatory cells and mediators they release alter the normal anatomic structure of the anterior chamber and aqueous drainage pathways of the eye. These changes alter the homeostatic mechanisms of intraocular pressure control. Management of glaucoma secondary to uveitis can be challenging due to the difficulties of managing the underlying disorder and its effects on the eye. This article reviews the pathogenesis of uveitic glaucoma in the horse and medical and surgical management options.     

Parenteral Anticholinergics in Dogs With Normal and Elevated Intraocular Pressure

Dogs given parenteral anticholinergic drugs have been thought to be at risk for development or exacerbation of elevated intraocular pressure (IOP). In a randomized, blinded, placebo-controlled study, we evaluated the effect of intramuscular glycopyrrolate (0.01 mg/kg) on pupil diameter and IOP in unanesthetized normal dogs. Treatment with glycopyrrolate did not change pupil diameter or IOP from baseline, nor were there differences between glycopyrrolate and saline-treated (control) dogs. In addition, the authors retrospectively reviewed the medical records of 2,828 dogs undergoing general anesthesia between April 1987 and September 1990 to determine if there was an association between parenteral anticholinergic medication and postanesthetic elevation in IOP. The authors also determined the frequency of bradycardia requiring anticholinergic therapy during anesthesia in dogs with glaucoma. Of the 2,828 cases reviewed, the records of 46 dogs coded for glaucoma were examined in detail. The 46 dogs underwent 62 episodes of anesthesia, with 23 episodes including exposure to an anticholinergic drug. An increase in IOP from preanesthetic to postanesthetic measurement occurred in three dogs. One of these dogs received anticholinergic medication for bradycardia during anesthesia. The postanesthetic elevation in IOP in this dog was probably not drug related. Preanesthetic anticholinergic administration did not affect the incidence of anticholinergic administration for bradycardia during the anesthetic episode. Anticholinergic therapy during anesthesia was more frequent when the preanesthetic medication included an opiate drug. These studies do not indicate an association between parenteral anticholinergic administration and elevations in IOP.     

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.