ABSTRACT OF THE WEEK

Veterinary ophthalmology
Volume 24 | Issue Suppl 1 (March 2021)

Pharmacologic ciliary body ablation for chronic glaucoma in dogs: A retrospective review of 108 eyes from 2013 to 2018.

Vet Ophthalmol. March 2021;24(Suppl 1):125-130.

Martha E Julien¹, Simone A Schechtmann², Tammy M Michau³, Anja Welihozkiy⁴, Terri L Baldwin⁵, Jessica M Stine⁶

¹ BluePearl Veterinary Partners, Tampa, FL, USA.; ² BluePearl Veterinary Partners, Tampa, FL, USA.; ³ BluePearl Veterinary Partners, Tampa, FL, USA.; ⁴ BluePearl Veterinary Partners, Sarasota, FL, USA.; ⁵ BluePearl Veterinary Partners, Clearwater, FL, USA.; ⁶ BluePearl Veterinary Partners, Clearwater, FL, USA.

Abstract

OBJECTIVE:To evaluate the long-term outcome and efficacy of intravitreal injection of gentamicin and dexamethasone sodium phosphate (IVGD) or triamcinolone in end-stage glaucoma patients and determine pre-procedure prognostic indicators of success and post-operative complications.

PROCEDURE:Medical records were reviewed for 108 dogs (108 eyes) treated with intravitreal gentamicin with or without dexamethasone sodium phosphate or triamcinolone for glaucoma between 2013 and 2018 with 3 months of minimum follow-up. Signalment and clinical findings, including type of glaucoma, pre-procedure intraocular pressure (IOP), chronicity, procedure protocol, and outcome were recorded. Success was defined as an intraocular pressure of ≤25 mm Hg at the time of last re-examination or no ocular hypotensive medications at 3 months or longer post-injection.

RESULTS:The overall success rate for pharmacologic ablation was 95%. The success rate for dogs receiving no ocular hypotensive medications was 86%. Seventy-six eyes (70.4%) had primary glaucoma, and 32 eyes (29.6%) had secondary glaucoma. Age at the time of injection had no effect on initial success but did in final success (P =-.03) for dogs requiring repeat injections. Cocker Spaniels required the most repeat 2nd and 3rd injections (3/12 dogs) and (2/4 dogs), respectively. No preoperative variable significantly affected the success rate. The most common complications were phthisis bulbi (59.2%), corneal edema (25.9%), and ulcerative keratitis (22.3%). Uncontrolled IOP resulted in enucleation in two dogs (1.8%).

CONCLUSIONS:Pharmacologic ablation has a high overall success rate in lowering IOP to ≤25 mm Hg short-term in blind, glaucomatous canine eyes. Type of glaucoma, pre-procedure IOP, chronicity, and protocol did not affect success.

Companion Notes

Retrospective report on pharmacologic ciliary body ablation for chronic glaucoma in 108 dogs

- intravitreal gentamicin and dexamethasone sodium phosphate or triamcinolone

Introduction on the treatment of chronic glaucoma

- primary glaucoma is typically genetic

(bilateral with predisposition for certain breeds)

- has 2 main forms based on gonioscopy of the drainage angle

- primary open angle glaucoma

- primary closed angle glaucoma

- secondary glaucoma is associated with ocular and systemic diseases

- painful and difficult to manage with medical and surgical intervention

- pharmacologic ablation of the ciliary body or ciliary body ablation (CBA)

- generally doesn’t require anesthesia

- owners may prefer it cosmetically compared to enucleation or evisceration

- procedure involves vitreocentesis

- followed by an injection of dexamethasone sodium phosphate

- in conjunction with a recommended dose of 15-30 mg gentamicin

- gentamicin is toxic to the ciliary body epithelium

- previously reported success rate in lowering IOP: 65%

- 86.4% reported more recently for ciliary body ablation with gentamicin

Study design

- study population: dogs seen at ophthalmology service of 4 referral hospitals

- inclusion criteria:

- end-stage glaucoma

- chronic glaucomatous, avisual eyes refractory to medical therapy

- diagnosis of chronic glaucoma was based on the following:

- IOP ≥ 25 mm Hg

- absent menace response and dazzle reflexes

- ocular changes, including the following:

- episcleral injection

- buphthalmos

- corneal edema

- secondary lens luxation or subluxation

- posterior segment changes noted included the following:

- optic nerve atrophy

- optic disk cupping

- retinal vascular attenuation

- intravitreal gentamicin

- with or without dexamethasone sodium phosphate or triamcinolone

- 3 month minimum followup

- exclusion criteria:

- previous glaucoma surgery

- previous diagnosis of intraocular neoplasia

- history and signalment

- mean age of the 108 dogs in study at time of the procedure:

- 9.5 ± 2.7 years with a range of 2-16 years

- breeds represented by 5 or more cases

- cocker spaniel, overrepresented with 24 cases

- shih tzu, 8

- Labrador retriever, 6

- Siberian husky, 5

- Bichon Frise, 5

- procedure: records between 2013 and 2018 retrospectively reviewed

- 1 eye from bilateral cases randomly selected for analysis

- success defined as intraocular pressure ≤ 25 mm Hg at last re-examination

- or no ocular hypotensive medications at 3 months or longer post-injection

- diagnosis of canine primary glaucoma based on the following:

- elevated intraocular pressure

- optic nerve changes

- lack of readily identifiable concurrent ocular or systemic diseases

(on routine ophthalmic examination)

- causes of secondary glaucoma included the following:

- hypermature cataracts

- lens luxation

- pigmentary uveitis

- cataract surgery

- retinal detachment

- chronic uveitis

- lipid uveitis

- trauma

- procedure (dogs had sedation or anesthesia for bilateral procedures)

- intended eye(s) aseptically prepared with 0.5% betadine solution

- topical proparacaine hydrochloride 0.5% applied

- followed by topical phenylephrine 2.5%

- for conjunctival and episcleral hemostasis

- vitreocentesis using 25 gauge, 1-inch hypodermic needle

- inserted 6-8 mm posterior to the limbus to reduce IOP

- 0.5-0.6 mL of vitreous aspirated

- followed by 30-50 mg of gentamicin (100 mg/mL)

(1 ophthalmologist based dose on dog’s weight and another used

a standard dose of 30 mg)

- combined with 1 of the following:

(for injection-related inflammation)

- 0.4 mg of dexamethasone sodium phosphate (4 mg/mL)

- 1-2 mg of triamcinolone (2 mg/mL)

- immediate post-injection IOP recorded

- if IOP remained ≥ 25 mm Hg, aqueocentesis performed

- using 27-30 gauge, 1-inch hypodermic needle

Results

- overall success rate: 95%

- success rate for dogs receiving no ocular hypotensive medications: 86%

- type of glaucoma in the 108 eyes

- 76 eyes (70.4%) had primary glaucoma

- 32 (29.6%) had secondary glaucoma

- cataract surgery, 14 eyes

- hypermature cataracts, 6

- pigmentary uveitis, 4

- retinal detachment, 3

- anterior lens luxation, 2

- single eyes with either anterior uveitis, trauma, or lipid uveitis, 0.9%

- effect of age at the time of injection

- no effect on initial success

- did effect final success for dogs requiring repeat injections

- all cases that needed repeat injections were 6 years or older

- 12 dogs required a 2^nd intravitreal injection

- at a mean of 208 ± 157.9 days after the first

- 3^rd injection, 4 dogs

- cocker spaniels required the most repeat injections

(3 of 12 required a 2^nd injection and 2 of 4 required a 3^rd injection)

- no preoperative variable found to significantly affect the success rate

- including type of steroid used and the dose of both steroid and gentamicin

- complications

- phthisis bulbi, 59.2%

- corneal edema, 25.9%

- ulcerative keratitis, 22.3%

- subconjunctival hemorrhage, 9.2%

- hyphema, 8.3%

- cataracts, 6.4%

- endophthalmitis, 3%

- enucleation due to uncontrolled IOP, 2 dogs

“Primary versus secondary glaucoma cases did not show a difference in the success rate. Moreover, neither lens luxation as a cause of secondary glaucoma nor chronicity of disease affected the success rate.”

Keywords

canine; ciliary body ablation; gentamicin; glaucoma; intravitreal injection; pharmacologic ablation;

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