Search Results

You are looking at 1 - 10 of 31 items for

  • Author or Editor: Daniel A. Ward x
  • Refine by Access: All Content x
Clear All Modify Search
Author:

Abstract

Objective

To compare the relative efficacies of 4 topical nonsteroidal anti-inflammatory drugs at preventing blood-aqueous barrier (BAB) disruption in dogs.

Design

1 eye of each dog was treated with 1 % suspensions of diclofenac, flurbiprofen, suprofen, or tolmetin, or with control solution. After 4 applications of eyedrops at 10-minute intervals, BAB disruption was induced in the treated eye by anterior chamber paracentesis. The severity of BAB disruption was measured by anterior chamber fluorophotometry.

Animals

40 ocular-normal dogs.

Procedure

After pretreatment with eyedrops, rapid, 100-μl nonleaking anterior chamber paracentesis was performed in 1 eye of each dog to induce BAB disruption. 1 day after paracentesis, 1 ml of 10% fluorescein sodium was injected IV. The amount of fluorescein entering the anterior chamber of each eye was measured 30 to 60 minutes later by use of a computerized scanning fluorophotometer. The degree of BAB disruption was determined by comparing the amount of fluorescein entering the aqueous humor of the paracentesed eye with that of the nonparacentesed eye.

Results

At postparacentesis day 1, the order of statistically significant BAB-stabilizing efficacy among groups was: diclofenac > flurbiprofen > suprofen > tolmetin = control solution.

Conclusions

Topically applied 1% suspensions of diclofenac, flurbiprofen, and suprofen are effective at preventing BAB disruption after paracentesis in dogs, indicating their potential usefulness for treatment of prostaglandm-mediated ocular disease. 1 % tolmetin is no more effective than control solution. (Am J Vet Res 1996;57:875–878)

Free access
in American Journal of Veterinary Research

Abstract

Objective—To determine tear volume, turnover rate, and flow rate in ophthalmologically normal horses by use of fluorophotometry.

Animals—12 mares free of ophthalmic disease.

Procedures—2 μL of 10% sodium fluorescein was instilled onto 1 eye of each horse, and tear samples were collected via microcapillary tubes from the inferonasal conjunctival culde-sac at 0, 2, 4, 6, 10, 15, and 20 minutes after instillation. Collected tear samples were then measured for fluorescein concentrations with a computerized scanning ocular fluorophotometer. A decay curve plot of concentration changes over time was used to determine tear flow rate and volume through 2 different mathematical treatments of the data (the including method and the excluding method).

Results—Fluorescein concentration in tears decreased in a first-order manner. The including method yielded a mean tear volume of 360.09 μL, a turnover rate of 12.22%/min, and a flow rate of 47.77 μL/min. The excluding method yielded values of 233.74 μL, 13.21%/min, and 33.62 μL/min, respectively. Mean ± SD correlation coefficients for the natural logarithm of the fluorescein concentration versus time were 0.93 ± 0.12 for the including method and 0.98 ± 0.03 for the excluding method.

Conclusions and Clinical Relevance—The excluding method yielded more accurate results. A tear flow rate of 33.62 μL/min and a tear volume of 233.74 μL imply a complete recycling of the tear volume in approximately 7 minutes and suggest that increased dosing regimens or constant infusion methods for topical administration of ophthalmic drugs may be indicated when treating horses for corneal disease in which high ocular surface concentrations are needed.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine aqueous humor flow rate (AHFR) in an avian species by use of anterior segment fluorophotometry.

Animals—9 healthy red-tailed hawks (Buteo jamaicensis; 4 males and 5 females) that ranged from 8 months to 8 years of age.

Procedures—A protocol was developed for fluorophotometric determination of AHFR. Topical administration of 10% fluorescein was used to load the corneas, and corneal and aqueous humor fluorescein concentrations were measured approximately 5, 6.5, and 8 hours later. Concentration-versus-time plots were generated, and slopes and cornea-to-aqueous humor concentration ratios from these plots were used to manually calculate flow rates.

Results—Mean ± SD AHFRs for the right eye, left eye, and both eyes were 3.17 ± 1.36 μL/min (range, 1.67 to 6.21 μL/min), 2.86 ± 0.88 μL/min (range, 2.04 to 4.30 μL/min), and 2.90 ± 0.90 μL/min (range, 1.67 to 4.42 μL/min), respectively. The AHFRs were similar for right and left eyes. These flow rates represented a mean aqueous humor transfer coefficient of 0.0082/min, which is similar to that of mammalian species.

Conclusions and Clinical Relevance—The AHFR in red-tailed hawks was similar to that of most mammalian species, and the fractional egress was almost identical to that of other species. This information will allow a greater understanding of aqueous humor flow in avian eyes, which is crucial when evaluating diseases that affect avian eyes as well as medications that alter aqueous humor flow.

Full access
in American Journal of Veterinary Research
in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine aqueous humor flow rate in clinically normal dogs, using fluorophotometry.

Animals—20 clinically normal Beagles.

Procedure—A study was performed on 5 dogs to establish an optimal protocol for fluorophotometric determination of aqueous humor flow rate. This protocol then was used to measure aqueous humor flow rate in 15 dogs. Corneas were loaded with fluorescein by topical application, and corneal and aqueous humor fluorescein concentrations were measured 5, 6.5, and 8 hours after application. Concentration-versus- time plots were generated, and slopes and ratios of the fluorescein concentration in the cornea and aqueous humor from these graphs were used to calculate flow rates. Calculations were performed by use of automated software provided with the fluorophotometer and by manual computation, and the 2 calculation methods were compared.

Results—The protocol established for the 5 dogs resulted in semilogarithmic and parallel decay of corneal and aqueous humor concentrations. Manually calculated mean ± SD aqueous humor flow rates for left, right, and both eyes were 5.58 ± 2.42, 4.86 ± 2.49, and 5.22 ± 1.87 μl/min, respectively, whereas corresponding flow rates calculated by use of the automated software were 4.54 ± 3.08, 4.54 ± 3.10, and 4.54 ± 2.57 μl/min, respectively. Values for the left eye were significantly different between the 2 computation methods.

Conclusions and Clinical Relevance—Aqueous humor flow rates can be determined in dogs, using fluorophotometry. This technique can be used to assess pathologic states and medical and surgical treatments that alter aqueous humor dynamics. (Am J Vet Res 2001;62:853–858)

Full access
in American Journal of Veterinary Research

Abstract

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 μl 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 μl/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. (Am J Vet Res 2001;62:859–863)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate the hemodynamic effects of orally administered carvedilol in healthy dogs with doses that might be used to initiate treatment in dogs with congestive heart failure.

Animals—24 healthy dogs.

Procedure—Dogs were randomly allocated to receive carvedilol PO at a dose of 1.56, 3.125, or 12.5 mg, twice daily for 7 to 10 days; 6 dogs served as controls. Investigators were blinded to group assignment. Hemodynamic variables were recorded prior to administration of the drug on day 1 and then 2, 4, and 6 hours after the morning dose on day 1 and days 7 to 10. Change in heart rate after IV administration of 1 µg of isoproterenol/kg and change in systemic arterial blood pressure after IV administration of 8 µg of phenylephrine/kg were recorded 2 and 6 hours after administration of carvedilol.

Results—Administration of carvedilol did not significantly affect resting hemodynamic variables or response to phenylephrine. The interaction of day and carvedilol dose had a significant effect on resting heart rate, but a significant main effect of carvedilol dose on resting heart rate was not detected. Increasing carvedilol dose resulted in a significant linear decrease in heart rate response to isoproterenol.

Conclusions and Clinical Relevance—In healthy conscious dogs, orally administered carvedilol at mean doses from 0.08 to 0.54 mg/kg given twice daily did not affect resting hemodynamics. Over the dose range evaluated, there was a dose-dependent attenuation of the response to isoproterenol, which provided evidence of β-adrenergic receptor antagonism. (Am J Vet Res 2005;66:637–641)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine effects of commonly used ophthalmic antibiotics on cellular morphologic characteristics and migration of canine corneal epithelium in cell culture.

Sample Population—Corneal epithelial cells harvested from corneas of 12 euthanatized dogs and propagated in cell culture.

Procedure—Cells were treated with various antibiotics after a defect was created in the monolayer. Cellular morphologic characteristics and closure of the defect were compared between antibiotic-treated and control cells.

Results—Cells treated with ciprofloxacin and cefazolin had the greatest degree of rounding, shrinkage, and detachment from plates. Cells treated with neomycin-polymyxin B-gramicidin and gentamicin sulfate had rounding and shrinkage but with less detachment. Cells treated with tobramycin and chloramphenicol grew similarly to control cells. On the basis of comparisons of defect circumference between control cells and cells exposed to antibiotics, tobramycin affected cellular migration the least.

Conclusion and Clinical Relevance—Effects of ciprofloxacin and cefazolin on morphologic characteristics of canine corneal epithelial cells in vitro should be taken into consideration before using these antibiotics for first-line of treatment for noninfected ulcers. Of the antibiotics tested that have a primarily gramnegative spectrum of coverage, gentamicin inhibited corneal epithelial cell migration and had greater cytopathologic effects than tobramycin did. For antibiotics with a gram-positive coverage, chloramphenicol had no cytopathologic effects on cells in comparison to cefazolin, which caused most of the cells to shrink and detach from the plate. Polymyxin B-neomycingramicidin was midrange in its effects on cellular morphologic characteristics and migration. (Am J Vet Res 2001;62:xxx–xxx)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine the duration of effect and the effect of multiple doses of topical ophthalmic application of 0.5% proparacaine hydrochloride on corneal sensitivity in clinically normal dogs.

Animals—8 clinically normal dogs.

Procedure—Dogs were randomly allocated to treatment order in a 2 × 2 (period × treatment) crossover study. Treatments consisted of topical application of ophthalmic 0.5% proparacaine (1 drop or 2 drops at a 1-minute interval); treatments were applied to both eyes. A Cochet-Bonnet aesthesiometer was used to determine corneal touch threshold (CTT) before corneal application, 1 and 5 minutes after corneal application, and at 5-minute intervals thereafter for 90 minutes.

Results—The CTT value before treatment differed significantly from CTT values after treatment until 45 minutes after application in the 1-drop group and until 55 minutes after application in the 2-drop group. As determined by use of the Cochet-Bonnet aesthesiometer, a significantly greater anesthetic effect was detected for the 2-drop treatment, compared with the effect for the 1-drop treatment, at 30, 35, 40, 45, 50, and 55 minutes after application. Maximal anesthetic effect lasted for 15 minutes for the 1-drop treatment and 25 minutes for the 2-drop treatment.

Conclusions and Clinical Relevance—Duration of corneal anesthetic effect induced by topical ophthalmic application of 0.5% proparacaine in dogs of this study is considerably longer than that reported elsewhere. Serial application of doses of 0.5% proparacaine increases the duration and magnitude of corneal anesthetic effects. (Am J Vet Res 2005;66:77–80)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine ocular tissue drug concentrations after topical ocular administration of 0.3% ciprofloxacin and 0.5% moxifloxacin in ophthalmologically normal horses.

Animals—24 ophthalmologically normal adult horses.

Procedures—0.3% ciprofloxacin and 0.5% moxifloxacin solutions (0.1 mL) were applied to the ventral conjunctival fornix of 1 eye in each horse as follows: group 1 (n = 8) at 0, 2, 4, and 6 hours; group 2 (8) at 0, 2, 4, 6, and 10 hours; and group 3 (8) at 0, 2, 4, 6, 10, and 14 hours. Tears, cornea, and aqueous humor (AH) were collected at 8, 14, and 18 hours for groups 1, 2, and 3, respectively. Drug concentrations were determined via high-performance liquid chromatography.

Results—Median (25th to 75th percentile) concentrations of ciprofloxacin for groups 1, 2, and 3 in tears (μg/mL) were 53.7 (25.5 to 88.8), 48.5 (19.7 to 74.7), and 24.4 (15.4 to 67.1), respectively; in corneal tissue (μg/g) were 0.95 (0.60 to 1.02), 0.37 (0.32 to 0.47), and 0.48 (0.34 to 0.95), respectively; and in AH were lower than the limit of quantification in all groups. Concentrations of moxifloxacin for groups 1, 2, and 3 in tears (μg/mL) were 188.7 (44.5 to 669.2), 107.4 (41.7 to 296.5), and 178.1 (70.1 to 400.6), respectively; in corneal tissue (μg/g) were 1.84 (1.44 to 2.11), 0.78 (0.55 to 0.98), and 0.77 (0.65 to 0.97), respectively; and in AH (μg/mL) were 0.06 (0.04 to 0.08), 0.03 (0.02 to 0.05), and 0.02 (0.01 to 0.04), respectively. Corneal moxifloxacin concentrations were significantly higher in group 1 than groups 2 and 3.

Conclusions and Clinical Relevance—After topical ocular administration, fluoroquinolones can reach therapeutic concentrations in tears and corneal tissue of horses, even when there is an intact epithelium.

Full access
in American Journal of Veterinary Research