Long-term vision outcomes and breed differences of Ahmed Glaucoma Valve implantation in 132 eyes of 122 dogs.

OBJECTIVE: To evaluate the long-term vision outcomes of Ahmed glaucoma valve (AGV) implantation in dogs. PROCEDURES: The medical records of dogs that underwent AGV implantation from January 2010 to December 2019 were reviewed to assess the duration of post-surgical vision preservation (PVP). The relationship between PVP and the underlying cause of glaucoma, implant placement, and preoperative intraocular pressure was evaluated. RESULTS: One hundred and thirty-two eyes of 122 dogs (mean age, 8.3 ± 2.6 years) were included. The mean ± standard error of PVP for all eyes was 57.5 ± 3.9 months. PVP in the dogs with primary acute glaucoma and prior history of cataract surgery was 56.4 ± 4.7 and 59.3 ± 5.9 months, respectively (p = .712). The PVP of the Shiba Inu, American Cocker Spaniel, and other breeds was 63.1 ± 5.5, 33.7 ± 5.3, and 59.1 ± 6.3 months, respectively (p < .05). The PVP in dogs with medial implantation was 61.9 ± 4.7 months, and in those with lateral implantation was 45.4 ± 6.4 months (p = .034). Among the 132 eyes investigated, 48 (36.4%) lost vision by the last follow-up, and 18 eyes retained vision for more than 5 years. Two of the total number of eyes retained their vision for more than 8 years. CONCLUSIONS: The vision outcomes regarding the use of AGV for the management of canine glaucoma were favorable in dogs.

Efficacy of biodegradable collagen matrix (Ologen® CM) in augmenting the success rate of Ahmed glaucoma valve implantation in canine glaucoma.

OBJECTIVE: To prospectively assess the efficacy of a biodegradable collagen matrix (ologen) in dogs with uncontrolled glaucoma receiving an Ahmed glaucoma valve (AGV) implant. ANIMAL STUDIED: Five client-owned dogs with glaucoma (five eyes). PROCEDURES: Five eyes treated for uncontrolled glaucoma underwent AGV implantation with ologen. Ologen was placed on the AGV plate and tube with a scleral flap. Complete ophthalmological examinations were performed preoperatively and at 1 and 3 days, 1 and 2 weeks, and 1, 2, 3, and 6 months postoperatively. Surgical outcomes were assessed based on the intraocular pressure (IOP), vision, frequency of anti-glaucoma eye drops, and bleb morphology; complications, if any, were recorded. The number of dogs with an IOP <20 mmHg with or without topical medications were tabulated and compared to those with an IOP ≥20 mmHg or those requiring surgery to maintain the IOP at <20 mmHg. RESULTS: The IOP significantly decreased from 47.00 ± 5.09 mmHg preoperatively to 17.00 ± 0.71 mmHg 6 months postoperatively (p = .008). IOP was controlled (<20 mmHg) in 5/5 dogs at 6 months postoperatively. Brief periods of elevated IOP (IOP ≥ 20 mmHg, IOP spike) occurred in one eye (case 5) at 1 month (35 mmHg) and 2 months (33 mmHg) postoperatively. The anti-glaucoma eye drop frequency decreased from 3.2 ± 0.44 preoperatively to 1.6 ± 0.90 at 6 months postoperatively (p = .007). CONCLUSIONS: To our knowledge, this is the first study to assess the potential safety of AGV implantation with ologen for canine glaucoma. This method effectively controlled the IOP, without any adverse effects.

Outcomes of baervedlt implant surgery in 17 dogs (20 eyes) with primary closed-angle glaucoma (2013-2019).

OBJECTIVE: To report outcomes and follow-up of Baerveldt implant surgery in dogs with primary closed-angle glaucoma (PCAG). MATERIALS AND METHODS: Record review of client-owned dogs with PCAG that underwent Baerveldt implant surgery during a 6-year period. Postoperative intraocular pressure (IOP), vision and daily number of anti-glaucoma drops at fixed time points (3, 12, and 24 months) were compared with preoperative values; complications were recorded. Success was defined as IOP <20 mm Hg and a positive menace response and navigation/tracking ability. RESULTS: Twenty eyes (17 dogs) were included. Mean follow-up was 575 days (range 30-1767 days) from implant surgery to last examination. Three months postoperatively 15/20 (75%) eyes had IOP <20 mm Hg and 14/20 (70%) eyes had vision. Twelve months postoperatively 11/17 (65%) eyes had IOP <20 mm Hg and 12/19 (63%) eyes had vision. Twenty-four months postoperatively 8/14 (57%) eyes had IOP <20 mm Hg and 7/15 (47%) eyes had vision. Denominators differ between time points as eyes were included when duration after surgery reached the relevant postoperative time point or failure was documented earlier. Within 3 months postoperatively 16/20 (80%) eyes had ≥1 complication, including transient IOP >20 mm Hg (14/20; 70% eyes), fibrin (12/20; 60% eyes), and hypotony (4/20; 20% eyes). After 3 months, postoperatively 13/16 (81%) eyes had ≥1 complication, including cataracts (13/16; 81% eyes), bleb fibrosis (3/16; 19% eyes), and conjunctival wound breakdown (1/16; 6% eyes). One patient (1 eye) was euthanized for blindness and 5/20 (25%) eyes were enucleated. CONCLUSIONS: The technique was effective in controlling IOP and maintaining vision in most dogs in this study.

A new, minimally invasive procedure for dogs with encapsulated Ahmed drainage implants and elevated intraocular pressures: A case series.

OBJECTIVE: To describe a novel, minimally invasive method for re-establishing aqueous humor outflow in dogs with refractory glaucoma after fibrous encapsulation of their Ahmed drainage implants. PROCEDURE: Three dogs (4 eyes) underwent trans-capsular implantation of an Alcon EX-PRESS® glaucoma filtration device under sedation (2 dogs) or general anesthesia (1 dog). After rotating the eye downwards, a 2 mm incision was made in the conjunctiva/Tenon's capsule overlying the encapsulated Ahmed plate, and later closed with absorbable suture. All eyes received subconjunctival mitomycin-C 0.02 mg. RESULTS: Mean post-operative follow-up was 341 days (range: 77-530). All eyes were hypertensive pre-operatively (mean IOP: 31.25 ± 7.14 mmHg) despite receiving topical latanoprost (4/4), timolol (4/4), carbonic anhydrase inhibitors (4/4), and demecarium bromide (2/4). Two eyes (dogs 1 and 2) were visual pre-operatively, while 2 eyes (dog 3) displayed equivocal or no vision. Post-operatively, all eyes received timolol and a carbonic anhydrase inhibitor. Other anti-hypertensive medications were discontinued. Immediately following surgery, all eyes were mildly hypotensive (mean IOP: 5.75 ± 1.71 mm Hg). Two of 4 eyes were normotensive and visual until days 90 (dog 2) and 530 (dog 1) (IOP range: 10-16 mm Hg). One eye (dog 3) was normotensive for approximately 150 days, and then hypertension returned. One eye (dog 3) from the start displayed severe uveitis, hypertensive episodes, and was phthisical by the end of follow-up. CONCLUSIONS: Trans-capsular EX-PRESS® implantation is a minimally invasive procedure for treatment of refractory glaucoma in dogs with encapsulated Ahmed drainage implants, and further investigation is warranted.

The impact of conjunctival flap method and drainage cannula diameter on bleb survival in the rabbit model.

PURPOSE: To examine the effect of cannula diameter and conjunctival flap method on bleb survival in rabbits undergoing cannula-based glaucoma filtration surgery (GFS). METHODS: Twelve New Zealand White rabbits underwent GFS in both eyes. The twenty-four eyes were divided into four groups. Two of the four groups (N = 12) received limbus-based conjunctival flaps (LBCF), and the other two (N = 12) received fornix-based conjunctival flaps (FBCF). Six FBCF rabbit eyes were implanted with 22-gauge drainage tubes, and the other six were implanted with 26-gauge tubes. Likewise, six LBCF rabbits received 22-gauge drainage tubes and six received 26-gauge tubes. Filtration blebs were evaluated every three days by a masked observer. Bleb failure was defined as the primary endpoint in this study and was recorded after two consecutive flat bleb evaluations. RESULTS: Group 1 (LBCF, 22- gauge cannula) had a mean bleb survival time (Mean ± SD) of 18.7 ± 2.9 days. Group 2 (LBCF, 26-gauge cannula) also had a mean bleb survival time of 18.7 ± 2.9 days. Group 3 (FBCF, 22-gauge cannula) had a mean bleb survival time of 19.2 ± 3.8 days. Group 4 (FBCF, 26-gauge cannula) had a mean bleb survival time of 19.7 ± 4.1 days. A 2-way analysis of variance showed that neither surgical approach nor cannula gauge made a statistically significant difference in bleb survival time (P = 0.634 and P = 0.874). Additionally, there was no significant interaction between cannula gauge and conjunctival flap approach (P = 0.874), suggesting that there was not a combination of drainage gauge and conjunctival flap method that produced superior bleb survival. CONCLUSION: Limbus and fornix-based conjunctival flaps are equally effective in promoting bleb survival using both 22 and 26-gauge cannulas in the rabbit model. The 26-gauge drainage tube may be preferred because its smaller size facilitates the implantation process, reducing the risk of corneal contact.

Comparison of diode laser trans-scleral cyclophotocoagulation versus implantation of a 350-mm2 Baerveldt glaucoma drainage device for the treatment of glaucoma in dogs (a retrospective study: 2010-2016).

OBJECTIVE: To compare outcomes following trans-scleral cyclophotocoagulation (TSCP) and 350-mm2 Baerveldt implantation in the treatment of canine refractory glaucoma. DESIGN: Retrospective case study. CASE SELECTION: Client owned dogs undergoing surgical treatment of glaucoma within a veterinary referral hospital. PROCEDURES: Eighty-six glaucoma surgeries were performed on 83 eyes (69 dogs) diagnosed with primary or secondary glaucoma. Medical records were retrieved, and baseline data, surgery, medications, intraocular pressures (IOPs), vision, and complications were extracted. RESULTS: Fifty-four eyes (44 dogs) were treated with TSCP and placement of an anterior chamber suture shunt; 28 eyes (24 dogs) were implanted with a Baerveldt glaucoma drainage device (GDD); and four eyes (4 dogs) underwent GDD implantation after failure of TSCP to manage IOP. Following TSCP, IOP control (<20 mmHg) and vision retention occurred in 81.5% and 42.6%, respectively, for 16.1 ± 1.36 months. Following GDD implantation, 71.4% maintained IOP <20 mmHg and 69.6% maintained vision for 11.0 ± 0.94 months. IOP control without loss of vision was more likely following Baerveldt implantation (17/28; 60.7%) than TSCP (19/54; 35.2%) (P = 0.027). One eye had functional vision restored following GDD placement. IOP control without adjunctive medications was more likely following Baerveldt implantation (P = 0.02). CONCLUSIONS: In this study, eyes treated with Baerveldt GDD implantation were more likely to maintain IOP control and retain vision compared to eyes treated with TSCP and placement of an anterior chamber suture shunt. Lack of formal randomization, inconsistencies in surgical techniques and TSCP protocols, and potential unmeasured confounders must be considered when extrapolating from this retrospective study.

Use of a 350-mm2 Baerveldt glaucoma drainage device to maintain vision and control intraocular pressure in dogs with glaucoma: a retrospective study (2013-2016).

OBJECTIVE: To evaluate the 350-mm2 Baerveldt glaucoma drainage device (GDD) in dogs with refractory glaucoma when modifications to address postoperative hypotony (extraluminal ligature; intraluminal stent) and the fibroproliferative response (intraoperative Mitomycin-C; postoperative oral colchicine and prednisolone) are implemented as reported in human ophthalmology. DESIGN: Retrospective case series. ANIMALS: Twenty-eight client-owned dogs (32 eyes) including seven dogs (nine eyes) with primary glaucoma and 21 dogs (23 eyes) with secondary glaucoma. METHODS: The medical records of all dogs undergoing placement of a 350-mm2 Baerveldt GDD at a veterinary ophthalmology referral service between 2013 and 2016 were reviewed. Signalment, diagnosis, duration and previous treatment of glaucoma, previous intraocular surgery, IOP, visual, and surgical outcomes were recorded. RESULTS: IOP was maintained <20mmHg in 24 of 32 (75.0%) eyes. Fourteen eyes (43.8%) required no adjunctive treatments to maintain this IOP control. Fewer doses of glaucoma medication were required following surgery. Vision was retained in 18 of 27 (66.7%) eyes with vision at the time of surgery. No eyes that were blind at the time of surgery (n = 5) had restoration of functional vision. Complications following surgery included hypotony (26/32; 81.3%), intraocular hypertension (24/32; 75.0%), and fibrin formation within the anterior chamber (20/32; 62.5%). The average follow-up after placement of the GDD was 361.1 days (median 395.6 days). CONCLUSION: Efforts to minimize postoperative hypotony and address the fibroproliferative response following placement of a 350-mm2 Baerveldt GDD showed an increased success rate to other reports of this device in dogs and offers an alternative surgical treatment for controlling intraocular pressure in dogs with glaucoma.

Surgical Treatment of Canine Glaucoma: Filtering and End-Stage Glaucoma Procedures.

Canine glaucoma is a common cause of vision loss associated with raised intraocular pressure, and leads to damage of the retina and optic nerve head. In most cases, medical treatment alone cannot provide long-term management of intraocular pressure control and preservation of vision. Surgical intervention is usually recommended to either decrease aqueous humor production, or increase its outflow. Among the current available procedures, filtering techniques are aimed at increasing aqueous humor outflow. Proper surgical timing and a combination of cyclodestructive and filtering procedures have been recently suggested to improve the long-term success of surgical treatment in dogs. Bleb fibrosis and surgical failure are still common occurrences in filtration surgery with relapse of glaucoma and vision loss. End stage procedures, such as enucleation, evisceration with intrascleral prosthesis, and chemical ablation of the ciliary bodies are then recommended to address chronic discomfort in buphthalmic and blind eyes.

Long-term evaluation of the use of Ahmed gonioimplants in dogs with primary glaucoma: nine cases (2000-2008).

OBJECTIVE: To evaluate the outcome and describe the complications associated with use of an Ahmed gonioimplant in the treatment of glaucoma in dogs. DESIGN: Retrospective case series. ANIMALS: 9 client-owned sighted dogs (median age, 9 years) with primary glaucoma. Procedures-Medical records of dogs with primary glaucoma that underwent unilateral gonioimplant placement (in 2000 through 2008), during which a temporalis muscle fascia graft (n = 8) or porcine intestinal submucosa (1) was used to cover the implant tube as it exited the globe, were reviewed. All dogs were treated with mitomycin C in the conjunctival pocket intraoperatively and with tissue plasminogen activator immediately after surgery; 1% prednisolone acetate was applied to the implanted eye daily until failure of the implant. Medical intervention or additional surgery was performed when intraocular pressures (IOPs) were > 20 mm Hg or progressively increasing values were detected. RESULTS: After gonioimplant placement, IOP was controlled for a variable period in all dogs. Subsequently, IOP exceeded 20 mm Hg in 7 dogs (median postoperative interval, 326 days). Median interval to vision loss despite interventional surgery was 518 days (range, 152 to 1,220 days). Surgical intervention was necessary in 4 dogs to maintain satisfactory IOP. Implant extrusion attributable to conjunctival dehiscence or necrosis occurred in 4 dogs. At 365 days after surgery, 8 dogs retained vision, and 5 dogs retained vision throughout follow-up. CONCLUSIONS AND CLINICAL RELEVANCE: In dogs with medically refractory primary glaucoma, placement of a gonioimplant appears to be effective in maintaining vision.

Ahmed valve implantation to control intractable glaucoma after phacoemulsification and intraocular lens implantation in a dog.

An 11-year-old spayed female Miniature Poodle presented with bilateral senile cataracts. Treatment was cataract removal by phacoemulsification and intraocular lens implantation. Five hours after surgery the operated right eye was partially closed and painful. The right pupil was fully dilated, there was generalized corneal edema, and intraocular pressure (IOP) was increased. After 12 h of medication IOP was controlled. Ten weeks after surgery the owners reported cloudiness of right eye, and the dog was again evaluated. The IOP was again increased and an Ahmed valve was implanted. This case describes describe the progression of this case and benefits of controlling postcataract surgery glaucoma by the implantation of an Ahmed valve.

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.

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.