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Abstract

Objective—To develop and compare 3 techniques for retrobulbar injection of local anesthetic agents for ocular surgery and analgesia in dogs.

Design—Prospective study.

Animals—17 dogs (including 9 cadavers).

Procedures—Inferior-temporal palpebral (ITP), perimandibular, and combined superior-inferior peribulbar injection techniques were compared by assessing the distribution of latex after injection into the orbits of 5 canine cadavers; magnetic resonance imaging (MRI) evaluation of the distribution of contrast agent after injection in the retrobulbar space of 4 canine cadavers; and assessment of the efficacy and MRI evaluation of the anatomic distribution of injections of a lidocainecontrast agent mixture in 4 anesthetized, nonrecovery dogs. By use of the preferred technique (ITP), the ocular effects of lidocaine anesthesia were evaluated in 4 dogs; during a 2-week period after treatment, dogs underwent ophthalmic examination, Schirmer tear testing (STT), intraocular pressure (IOP) measurement, and Cochet–Bonnet esthesiometry.

Results—Of the 3 techniques, the ITP technique was the preferred method for retrobulbar administration of anesthetic agent in dogs because it was efficacious (pupil dilation and central rotation of the globe achieved in all eyes), easiest to perform, and provided thorough coverage of the intraconal retrobulbar space without complication. During the 2-week follow-up period, the ITP injection did not significantly affect STT, IOP, or Cochet-Bonnet esthesiometry values in dogs.

Conclusions and Clinical Relevance—In dogs, retrobulbar administration of anesthetic agents via the ITP technique is a potential alternative to systemic administration of neuromuscular blocking agents for ophthalmic surgery and provides the additional benefit of local ocular analgesia.

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To evaluate efficacy and safety of IP administration of high-molecular-weight carboxymethylcellulose (HMW CMC) for the prevention of postoperative intra-abdominal adhesions in ponies.

Animals—10 ponies.

Procedure—A 1% solution of HMW CMC was instilled intra-abdominally prior to surgery in 5 ponies, whereas 5 control ponies did not receive HMW CMC. Postoperative adhesions were induced by use of a bowel-abrasion method comprising laparotomy, typhlotomy, and abrasion of jejunal serosa at multiple sites with placement of 3 sutures at each site. Day of surgery was day 0. After surgery, ponies were monitored, and hematologic, serum biochemical, and peritoneal fluid analyses were performed on days 1, 2, 3, 5, 7, and 10. On day 10, ponies were euthanatized. Intra-abdominal adhesions were recorded, and tissue samples were collected for histologic examination.

Results—A significantly greater number of adhesions, number of multiple adhesions, and mean incidence of adhesions were identified in control ponies, compared with CMC-treated ponies. Mean peritoneal fluid WBC count on day 7 and serum fibrinogen concentrations on days 5 and 7 were significantly higher in control ponies, compared with CMC-treated ponies. Results of serum biochemical analyses did not differ significantly between the 2 groups.

Conclusions and Clinical Relevance—Intra-abdominal use of 1% HMW CMC during surgery was effective for preventing postoperative adhesions in ponies. Use of HMW CMC did not have detrimental effects on wound healing, intra-abdominal defenses, or patient health. A 1% solution of HMW CMC may be used routinely during abdominal surgery of horses for prevention of postoperative adhesions. (Am J Vet Res 2002;63:1448–1454)

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in American Journal of Veterinary Research

Abstract

Objective—To measure the effect of induced myopia on field trial performance in dogs.

Animals—7 Labrador Retrievers and 1 Chesapeake Bay Retriever trained in field trial competition.

Procedures—Dogs were commanded to retrieve targets at 137.2 m (150 yards). Each dog participated in 3 trials while their eyes were fitted with 0- (plano), +1.50-, or +3.00-diopter (D) contact lenses, applied in random order. Retrieval times were measured objectively, and dog performances were evaluated subjectively by masked judges.

Results—Retrieval times were significantly faster with plano lenses than with +1.50- or +3.00-D lenses, but there were no significant differences in times between +1.50- and +3.00-D lenses. Masked judges assigned the best performance scores to dogs with plano lenses and the lowest scores to dogs fitted with +3.00-D lenses.

Conclusions and Clinical Relevance—Even mild myopic defocusing had a significant negative impact on both the subjective and objective assessments of dogs' performances. Dogs with demanding visual tasks or signs of visual deterioration should be evaluated retinoscopically to determine the refractive state because they may have ametropia.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate propagation velocity of acoustic waves through the lens and vitreous body of pigs, dogs, and rabbits and determine whether there were associations between acoustic wave speed and age, temperature, and time after enucleation.

Sample Population—9 pig, 40 dog, and 20 rabbit lenses and 16 pig, 17 dog, and 23 rabbit vitreous bodies.

Procedure—Acoustic wave velocities through the ocular structures were measured by use of the substitution technique.

Results—Mean sound wave velocities in lenses of pigs, dogs, and rabbits were 1,681, 1,707, and 1,731 m/s, respectively, at 36°C. Mean sound wave velocities in the vitreous body of pigs, dogs, and rabbits were 1,535, 1,535, and 1,534 m/s, respectively, at 38°C. The sound wave speed through the vitreous humor, but not the lens, increased linearly with temperature. An association between wave speed and age was observed in the rabbit tissues. Time after enucleation did not affect the velocity of sound in the lens or vitreous body. The sound wave speed conversion factors for lenses, calculated with respect to human ocular tissue at 36°C, were 1.024, 1.040, and 1.055 for pig, dog, and rabbit lenses, respectively.

Conclusions and Clinical Relevance—Conversion factors for the speed of sound through lens tissues are needed to avoid underestimation of the thickness of the lens and axial length of the eye in dogs during comparative A-mode ultrasound examinations. These findings are important for accurate calculation of intraocular lens power required to achieve emmetropia in veterinary patients after surgical lens extraction.

Full access
in American Journal of Veterinary Research

Abstract

Case Description—A great horned owl of estimated age < 1 year that was captured by wildlife rehabilitators was evaluated because of suspected cataracts.

Clinical Findings—Nuclear and incomplete cortical cataracts were evident in both eyes. Ocular ultrasonography revealed no evidence of retinal detachment, and electroretinography revealed normal retinal function.

Treatment and Outcome—For visual rehabilitation, cataract surgery was planned and intraocular lens design was determined on the basis of values obtained from the schematic eye, which is a mathematical model representing a normal eye for a species. Cataract surgery and intraocular lens placement were performed in both eyes. After surgery, refraction was within −0.75 diopters in the right eye and −0.25 diopters in the left eye. Visual rehabilitation was evident on the basis of improved tracking and feeding behavior, and the owl was eventually released into the wild.

Clinical Relevance—In raptors with substantial visual compromise, euthanasia or placement in a teaching facility is a typical outcome because release of such a bird is unacceptable. Successful intraocular lens implantation for visual rehabilitation and successful release into the wild are achievable.

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To assess the refractive state of eyes in various breeds of dogs to identify breeds susceptible to ametropias.

Animals—1,440 dogs representing 90 breeds.

Procedures—In each dog, 1 drop of 1% cyclopentolate or 1% tropicamide was applied to each eye, and a Canine Eye Registration Foundation examination was performed. Approximately 30 minutes after drops were administered, the refractive state of each eye was assessed via streak retinoscopy. Dogs were considered ametropic (myopic or hyperopic) when the mean refractive state (the resting focus of the eye at rest relative to visual infinity) exceeded ± 0.5 diopter (D). Anisometropia was diagnosed when the refractive error of each eye in a pair differed by > 1 D.

Results—Mean ± SD refractive state of all eyes examined was −0.05 ± 1.36 D (emmetropia). Breeds in which the mean refractive state was myopic (≤ −0.5 D) included Rottweiler, Collie, Miniature Schnauzer, and Toy Poodle. Degree of myopia increased with increasing age across all breeds. Breeds in which the mean refractive state was hyperopic (≥ +0.5 D) included Australian Shepherd, Alaskan Malamute, and Bouvier des Flandres. Astigmatism was detected in 1% (14/1,440) of adult (≥ 1 year of age) dogs; prevalence of astigmatism among German Shepherd Dogs was 3.3% (3/90). Anisometropia was detected in 6% (87/1,440) of all dogs and in 8.9% (8/90) of German Shepherd Dogs.

Conclusions and Clinical Relevance—Refractive states of canine eyes varied widely and were influenced by breed and age. In dogs expected to have high visual function (eg, performance dogs), determination of refractive state is recommended prior to intensive training.

Full access
in American Journal of Veterinary Research

Abstract

OBJECTIVE To determine the mydriatic effects of topical rocuronium bromide administration in Hispaniolan Amazon parrots (Amazona ventralis) and to identify any adverse effects associated with treatment.

DESIGN Randomized crossover study.

ANIMALS 8 healthy adult Hispaniolan Amazon parrots.

PROCEDURES Rocuronium bromide (20 μL/eye; 10 mg/mL) or saline (20 μL/eye; 0.9% NaCl) solution was administered in both eyes of each bird with a 26-day washout period. The birds were manually restrained in lateral recumbency with the apex of the cornea positioned upward for 2 minutes following administration in each eye. Infrared pupillometry and direct pupillary light reflex measurements were used to evaluate the mydriatic effects. Pupillary measurements were recorded prior to administration and every 20 minutes for 2 hours after administration, then hourly for a total of 7 hours. A brief physical examination was performed, direct pupillary light reflex was tested, and fluorescein staining was performed on each eye of each bird 24 hours after administration.

RESULTS A significant difference in pupillary diameter for the active versus control treatment group was noted from 20 to 360 minutes after drug administration, but not at 420 minutes. Minimal adverse effects were noted. Three birds had transient inferior eyelid paresis noted in both eyes after receiving rocuronium; 24 hours after the treatment, no differences in ocular measurements existed between the active and control treatments.

CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that topical rocuronium bromide administration may be safely used for pupillary dilation in Hispaniolan Amazon parrots and could be used for clinical evaluation, fundus imaging, and surgical interventions involving the lens and posterior segment in this species.

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To characterize healing of corneal epithelial defects in horses and to evaluate the ability of epidermal growth factor (EGF) to modulate rate of corneal epithelial healing in horses.

Sample Population—20 eyes in 12 adult horses.

Procedure—Corneal epithelial wounds were created by mechanically debriding the limbus. Corneal healing was recorded for 3 treatment groups: 50 µg of EGF/ml (n = 5 eyes), 5 µg of EGF/ml (7), and PBS solution (8). Corneal healing was recorded once daily after instillation of fluorescein stain by use of photography and calculating the area of the wound, using imaging software.

Results—After corneal debridement, re-epithelialization was rapid and progressed in a linear fashion for the first 5 to 7 days after surgery in all groups. After that period, rates of healing decreased. A profound increase in the degree of inflammation, neovascularization, melanosis, and scarring was observed in eyes treated with the high dose of EGF (50 µg/ml), but there was not a statistical difference in mean healing time or in mean decrease in radius during the linear phase between the control and either EGF treatment groups. However, for all 8 horses in which both eyes were debrided, the first eye healed significantly faster than the second eye, regardless of treatment.

Conclusions and Clinical Relevance—Beneficial effects of topical administration of a high dose of EGF for acceleration of healing of corneal defects in eyes of horses are outweighed by the intensity of the associated inflammatory response. (Am J Vet Res 2000; 61:1150–1155)

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in American Journal of Veterinary Research

Abstract

Objective—To characterize the clinical and morphologic aspects of aqueous humor misdirection syndrome (AHMS) in cats and provide a hypothesis regarding its pathogenesis on the basis of detailed analysis of affected cats.

Design—Retrospective study.

Animals—32 cats (40 eyes).

Procedure—Medical records of cats in which AHMS was diagnosed from July 1997 to August 2003 were reviewed. In certain cats, results of additional diagnostic testing were also obtained, including A-scan, B-scan, and high-resolution ultrasonography; streak retinoscopy; video keratometry; and infrared neutralizing videoretinoscopy as well as results of analysis of flash-frozen sections and histologic examination of enucleated globes.

Results—Cats had a uniformly shallow anterior chamber, intact lens zonules, and a narrowed approach to an open iridocorneal angle. Mean age of affected cats was 11.7 years (range, 4 to 16 years), and female cats were significantly more often affected than male cats. Clinical signs included mydriasis, decreased pupillary light reflex, decreased menace response, and blindness. Glaucomatous changes to the optic nerve, incipient cataracts, and eventual blindness were seen. Intraocular pressure was ≥ 20 mm Hg (range, 12 to 58 mm Hg) in 32 of 40 eyes. Ultrasonography and histologic examination revealed a thickened anterior vitreal face interposed between the lens and ciliary body, partial ciliary cleft collapse, and cavitated vitreal regions. Various treatment modalities were used.

Conclusions and Clinical Relevance—AHMS affects older cats, especially females, and may result in glaucoma, vision loss, and signs of ocular pain. Topical administration of carbonic anhydrase inhibitors decreased intraocular pressure. (J Am Vet Med Assoc 2005;227:1434–1441)

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in Journal of the American Veterinary Medical Association