Effect of Volumes of Solutions on Intraocular Pressure During Intravitreal Injection of Low Dose Gentamicin in Horses With Recurrent Uveitis: A Randomized Controlled Study.

Horses with recurrent uveitis can be treated by intravitreal injection of low dose gentamicin under sedation and after local anesthetic techniques including the retrobulbar nerve block. Since it is reported that retinal degeneration can be secondary to an acute increase of intraocular pressure (IOP), the current randomized controlled study was carried out in order to investigate the changes in IOP following retrobulbar anesthesia, with two different volumes of local anesthetic (lidocaine) solution (10 and 5 mL), and intravitreal injection of 6 mg gentamicin in two different volumes of solution (0.3 and 0.15 mL). Multivariate regression showed that IOP was significantly lower in the pathologic eye at baseline (estimated effect size -6.1 mmHg; P = .0001) and after sedation (estimated effect size -9.4 mmHg; P < .0001). The IOP was significantly higher after a 10 mL block (P .0002) but this effect was very small (+0.5 mmHg). There was no significant difference in IOP after the injection of 0.15 or 0.3 mL solution of gentamicin. There was no significant combined effect of the volume of local anesthetic used for the block and the volume of the gentamicin solution. Since the expected anesthetic effects (desensitization and akinesia) were met in all cases, the smaller volume of 5 mL of lidocaine solution would be preferable for retrobulbar block for intravitreal injections, while intravitreal injections volumes of 0.15 and 0.30 mL can be used indifferently.

Clinical outcome of intravitreal gentamicin injection for the treatment of end-stage glaucoma in five rabbits (eight eyes).

Background: Glaucoma is a painful and blinding condition that occurs in many species, including rabbits. When medication is no longer effective in maintaining intraocular pressure (IOP), enucleation is the recognized treatment for rabbits with end-stage glaucoma. However, this procedure carries risks relating to the procedure and the anesthesia. Aim: The aim of this retrospective study was to report the efficacy of intravitreal gentamicin injection in controlling IOP in blind eyes of rabbits with end-stage glaucoma. Ocular and non-ocular complications were retrospectively assessed. Methods: Medical record review was performed to identify five client-owned rabbits (eight eyes) that were treated by intravitreal injection of 6-20 mg of gentamicin per eye (median 7.18 mg/kg) for chronic, end-stage glaucoma. Treatment was unilateral in two and bilateral in three rabbits. IOP control was assessed via rebound tonometry readings performed approximately 2 weeks, 1 month, 3 months, and 6 months after injection. Total follow-up was between 313 and 1,111 days. Ocular complications were recorded and systemic health was estimated by the owner-answered questionnaire and changes in body weight. Results: IOP was <25 mmHg in 87.5% of eyes 3 months post-injection. The most common ocular complications were cataracts (62.5%), anterior uveitis (25%), retinal detachment (12.5%), and corneal erosion (12.5%). There were no behavioral or body weight changes suggestive of systemic complications. Conclusion: 87.5% of rabbit eyes treated with intravitreal gentamicin had controlled IOP 3 months after injection. All eyes were blind at the time of injection. Ocular side effects were common. Investigation of the safety and systemic effects of intravitreal gentamicin injection is required; however, no overt complications were identified in treated rabbits in this study.

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

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.

Use of Intravitreal Injection of Gentamicin in 71 Horses With Equine Recurrent Uveitis.

We report a retrospective evaluation of intravitreal gentamicin (6 mg in 0.3 mL solution) injection in 71 horses with equine recurrent uveitis between 2010 and 2016. Aqueous flare and hyalitis were scored at the baseline in all horses, then at 15, 30, 60, 90, 180, 365, and 730 in 37, 46, 30, 25, 22, 18, and 11 horses, respectively. Forty-two animals had a global score of inflammation (sum of scores for aqueous flare and hyalitis) of zero at the last examination (number of re-examinations per horse ranged from 1 to 5). Among the 29 remaining horses, four were not reassessed after the intervention. The individual inflammation scores of the remaining 25 horses improved in 21 cases, whereas it slightly deteriorated in four cases (number of re-examinations ranged from 0 to 6). Ocular hypotension, lens opacities, and retinal folds were observed, respectively, in 92%, 78%, and 28% of the 71 eyes at the baseline, and in 80%, 90%, and 36% of the 11 eyes re-evaluated at 2 years. A telephone inquiry about all horses among owners and referring veterinarians conducted in 2016 at least 6 months after the more recent injections indicated that 70 horses did not develop a new observable episode of inflammation and did not need ocular medication. Although the results of this study should be discussed with reservation, it indicated that low-dose intravitreal injection of gentamicin could be a useful treatment to maintain ocular quiescence in equine recurrent uveitis.

Measurement of plasma gentamicin concentrations postchemical ciliary body ablation in dogs with chronic glaucoma.

OBJECTIVE: To investigate the absorption of gentamicin into the plasma after an intravitreal injection in dogs and to report the success rate of this procedure in lowering the intraocular pressure. ANIMALS: Twenty-four client-owned dogs with chronic, end-stage glaucoma. PROCEDURES: Dogs received a unilateral (22) or bilateral (2) intravitreal injection of 25-40 mg of gentamicin (mean ± SD dose 2.57 ± 1.65 mg/kg and range 0.61-7.50 mg/kg) and 1 mg of dexamethasone per eye. Blood samples were collected at various time points following the intravitreal injection. Plasma concentrations of gentamicin were determined by liquid chromatography and mass spectrometry. RESULTS: The total plasma concentration of gentamicin ranged from 0.21 to 9.71 µg/mL (mean ± SD 2.15 ± 2.03). The mean gentamicin CMAX was 2.29 µg/mL at 2.54 h with a terminal half-life of 9.8 h. The success rate of the chemical ablation procedure was 86.4% (19/22 eyes) in dogs that had at least 1 month of follow-up. CONCLUSIONS: Intravitreal injection of gentamicin in eyes with chronic glaucoma resulted in detectable plasma levels in dogs and was successful in lowering the intraocular pressure in 86.4% of the eyes after the first procedure.

Transient unilateral vision loss in a dog following inadvertent intravitreal injection of bupivacaine during a dental procedure.

CASE DESCRIPTION: A 4-year-old castrated male Chihuahua was evaluated because of unilateral vision loss following extraoral administration of a caudal maxillary nerve block during a dental procedure. CLINICAL FINDINGS: The menace response was absent in the left eye, but the pupillary light reflex was intact. Vitreal hemorrhages and opacities were present on ophthalmic examination of the left eye. Ultrasonographic findings were supportive of the clinical findings. The posterior lens capsule and retina appeared to be undisturbed. TREATMENT AND OUTCOME: Treatment consisted of administration of carprofen and prophylactic administration of amoxicillin-clavulanate. Vision was clinically normal with an intact menace response 1 week later. CLINICAL RELEVANCE: Findings indicated that intravitreal injection of the local anesthetic agent should be considered as a potential complication when performing nerve blocks prior to dental procedures in dogs.

Feline ocular tumors following ciliary body ablation with intravitreal gentamicin.

Practitioners approach chemical ciliary body ablation (CBA) in cats with caution. In 1994, an academic letter proposed a potential link between intraocular gentamicin injections for glaucoma and the appearance of ocular tumors in cats (Veterinary and Comparative Ophthalmology, 4, 1994, 166). There is an historic perceived risk for the development of feline ocular post-traumatic sarcoma following gentamicin ciliary body ablation, and many clinicians refrain from chemical ablation in cats for this reason. A recent study discussed the possibility of a correlation between intravitreal gentamicin and tumor promotion in dogs (Veterinary Ophthalmology, 16, 2013, 159). We searched the Comparative Ocular Pathology Laboratory of Wisconsin (COPLOW) database for cases of cats diagnosed with ocular tumors following ciliary body ablation. Of eight cases with historic gentamicin injection, five had malignant tumors: three post-traumatic sarcomas and two melanomas.

Canine ocular tumors following ciliary body ablation with intravitreal gentamicin.

Iridociliary tumors are the second most common primary ocular tumor in dogs and are usually benign. A review of the Comparative Ocular Pathology Laboratory of Wisconsin (COPLOW) database in 2009 suggested a potential correlation between malignant iridociliary epithelial tumors and ciliary body ablation by intravitreal gentamicin injection for the treatment of glaucoma. The purpose of this case series was to determine whether there is evidence of such a correlation in the COPLOW collection. Mining of the COPLOW database revealed that a significant number (39.5%) of canine globes with a history of ciliary body ablation were subsequently diagnosed with primary ocular tumors at enucleation, most commonly iridociliary epithelial tumors and melanocytic tumors. It is possible that neoplasia was present but unrecognized at the time of ciliary body ablation. These tumors had a higher than expected incidence of malignancy. These cases underscore the importance of reserving ciliary body ablation with gentamicin for disease-free eyes.