Daniel A. Ward

Normal Ocular Parameters and Characterization of Ophthalmic Lesions in a Group of Captive Bald Eagles (Haliaeetus leucocephalus)

Abstract: Sixteen adult captive bald eagles (Haliaeetus leucocephalus) underwent a complete bilateral ocular examination to assess normal ocular parameters and describe ophthalmic lesions. Tear production was measured with the Schirmer tear test 1 and intraocular pressure was measured with applanation tonometry. The menace response was normal bilaterally in 13 of 16 eagles. Two birds had normal menace responses despite having fundic lesions, and 2 birds with an inconsistent or absent menace response did not have appreciable ophthalmic lesions. Mean (SD) tear production was 14 ± 2 mm/min (range, 8–19 mm/min). Mean intraocular pressure was 21.5 ± 1.7 mm Hg (range, 15–26 mm Hg). At least 1 ocular lesion was present in 50% of examined eyes. Cataracts, the most common lesion observed, were present in 8 eyes of 5 birds. Three of 4 known geriatric birds were or had been affected with bilateral cataracts. Overall, ocular lesions are common in captive bald eagles, and cataracts appear to be more prevalent in geriatric bald eagles. An obvious positive menace response is present in most visual birds but may be absent in some eagles that are either normal or that do not have appreciable ophthalmic lesions. Applanation tonometry and the Schirmer tear test 1 can be performed easily on adult bald eagles and provide reproducible results.

The effect of a single dose of topical 0.005% latanoprost and 2% dorzolamide/0.5% timolol combination on the blood-aqueous barrier in dogs: a pilot study

OBJECTIVE To determine the effects of 0.005% latanoprost and 2% dorzolamide/0.5% timolol on the blood-aqueous barrier (BAB) in normal dogs. ANIMALS STUDIED Eight mixed-breed and pure-breed dogs. PROCEDURES Baseline anterior chamber fluorophotometry was performed on eight normal dogs. Sodium fluorescein was injected and the dogs were scanned 60-90 min post-injection. Seventy-two hours following the baseline scan, one eye received one drop of latanoprost. Fluorophotometry was repeated 4 h after drug administration. Following a washout period, the identical procedure was performed 4 h after the administration of dorzolamide/timolol. The degree of BAB breakdown was determined by comparing the concentrations of fluorescein within the anterior chamber before and after drug administration. BAB breakdown was expressed as a percentage increase in the post-treatment fluorescein concentration over the baseline concentration: %INC [Fl] = {([Fl](post)-[Fl](baseline))/[Fl](baseline)} x 100. The percentage increase in fluorescein concentration in the treated eye was compared to that in the nontreated eye using a paired t-test with significance set at P < or = 0.05. RESULTS Following administration of latanoprost, the fluorescein in the treated eyes increased 49% (+/- 58%) from baseline compared to 10% (+/- 31%) in the untreated eyes (P = 0.016). Following administration of dorzolamide/timolol, the fluorescein concentration increased 38% (+/- 54%) compared to baseline vs. 24% (+/- 38%) in the untreated eyes (P = 0.22). CONCLUSIONS The results of this study show that topical latanoprost may cause BAB disruption in normal dogs while topical dorzolamide/timolol may have no effect on the BAB in normal dogs.

Screening ADAMTS10 in dog populations supports Gly661Arg as the glaucoma-causing variant in beagles.

PURPOSE Previously, we mapped the disease locus in the beagle model of autosomal recessive primary open angle glaucoma (POAG) to a 4-Mb interval on chromosome 20, and identified a Gly661Arg variant in ADAMTS10 as the candidate disease-causing variant. The purpose of this study was to test the hypothesis that the Gly661Arg variant of ADAMTS10 causes glaucoma by genotyping dogs of various breeds affected and unaffected by primary glaucoma. METHODS Dogs of various breeds, affected or unaffected with primary glaucoma, were genotyped for the Gly661Arg variant of ADAMTS10, as well as 7 other nonsynonymous single nucleotide polymorphisms (SNPs) in other genes in the beagle POAG locus that segregate with disease. Alternate allele frequencies were calculated with 95% confidence intervals and comparisons made to expected allele frequency relative to disease prevalence or between cases and controls. RESULTS For the nonsynonymous SNPs other than the ADAMTS10 variant, control dogs were identified that were homozygous for the alternative alleles, ruling out those variants as causative. None of the nonsynonymous SNPs were found associated with primary glaucoma in American cocker spaniels. The Gly661Arg variant of ADAMTS10 was the only variant with minor allele frequency consistent with the prevalence of primary glaucoma in the general beagle population. The only dog found homozygous for the Gly661Arg variant of ADAMTS10 was an affected beagle, unrelated to the POAG colony. CONCLUSIONS These findings support the Gly661Arg mutation of ADAMTS10 as the likely cause of POAG in beagles.

An investigation comparing the efficacy of topical ocular application of tacrolimus and cyclosporine in dogs.

The purpose of this paper was to determine the efficacy and safety of topical tacrolimus, compared to cyclosporine, for treating keratoconjunctivitis sicca (KCS) in dogs. This study was a two-phase, randomized, controlled, masked clinical trial. Phase 1 evaluated ophthalmic 0.03% tacrolimus in normal dogs. Ocular examinations were performed daily. Phase 2 evaluated the efficacy of tacrolimus in treating KCS. Half the dogs received 2% cyclosporine A; the others received 0.03% tacrolimus, both diluted in olive oil. Four ophthalmic examinations were done over 12 weeks. There was no significant difference between groups in phase I. In phase 2, there was no significant difference in Schirmer tear test I (STT) results between the two groups, and both groups had a significant increase in STT over time. Both drugs were effective in increasing the STT in dogs naïve to lacrimostimulants. Tacrolimus was effective in increasing the STT in 4 dogs currently nonresponsive to cyclosporine.

Tear volume, turnover rate, and flow rate in ophthalmologically normal horses

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 microL 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 microL, a turnover rate of 12.22%/min, and a flow rate of 47.77 microL/min. The excluding method yielded values of 233.74 microL, 13.21%/min, and 33.62 microL/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 microL/min and a tear volume of 233.74 microL 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.

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.

Breed predisposition to congenital alacrima in dogs

OBJECTIVE To evaluate the clinical characteristics and breed predisposition of congenital alacrima in dogs. Animals studied Dogs with congenital keratoconjunctivitis sicca. PROCEDURES A search of the medical records of the University of Tennessee Veterinary Teaching Hospital from 1974-2005 and the University of California-Davis Veterinary Teaching Hospital from 1986-2006 for dogs under 1 year of age with a diagnosis of keratoconjunctivitis sicca (KCS) was performed. These cases were further reviewed for dogs with a Schirmers tear test I of <or= 5 mm/min before 6 months of age, with no known causes for KCS, which did not respond to appropriate KCS therapy; these cases were considered to have congenital alacrima. These breeds were compared to all other breeds using the Fishers exact test with correction for multiple comparisons. RESULTS Congenital alacrima was identified in 19 dogs representing 11 breeds and mixed breeds. Yorkshire Terriers and Bedlington Terriers were statistically overrepresented compared to reference populations (P < 0.01 and P = 0.04, respectively). CONCLUSIONS Yorkshire terriers are significantly at risk for congenital alacrima compared to other breeds. The significance of the increase in congenital alacrima in Bedlington Terriers in this study may not be clinically relevant and may be due to the small total number of dogs of this breed that presented to the both hospitals. Based on the poor response to therapy in humans with congenital alacrima, it may be prudent to offer guarded prognoses for KCS in juvenile Yorkshire terriers.

Effects of one-week versus one-day preoperative treatment with topical 1% prednisolone acetate in dogs undergoing phacoemulsification

OBJECTIVE To compare the effects of 2 preoperative anti-inflammatory regimens on intraocular inflammation following phacoemulsification. DESIGN Randomized controlled trial ANIMALS 21 dogs with immature cataracts. PROCEDURES All dogs had cataract surgery via phacoemulsification, and most received prosthetic intraocular lenses. Dogs were randomly divided into 2 groups. Group A dogs were treated topically with prednisolone acetate for 7 days prior to surgery, whereas prednisolone acetate treatment commenced the evening prior to surgery in group B dogs. Postoperative care was identical for both groups. Blood-aqueous barrier breakdown was quantified by use of anterior chamber fluorophotometry, with fluorescein entry into the anterior chamber measured 2 and 9 days after surgery compared with baseline scans obtained prior to surgery. Ophthalmic examinations were performed before surgery and 1 day, 9 days, 3 weeks, 7 weeks, 3 months, and 6 months after surgery. A subjective inflammation score was established at each examination. Intraocular pressures were measured 4 and 8 hours after surgery and at each follow-up examination. RESULTS There was no difference in the extent of blood-aqueous barrier disruption between the groups at 2 or 9 days after surgery. Subjective inflammation scores were also similar at most time points. Dogs in group A developed postoperative ocular hypertension at a higher frequency (60%) than did those in group B (18%). CONCLUSIONS AND CLINICAL RELEVANCE In dogs that underwent cataract surgery via phacoemulsification, a full week of topical prednisolone acetate treatment prior to surgery did not decrease postoperative inflammation, compared with commencement of topical prednisolone acetate treatment the evening prior to surgery, and was associated with a greater incidence of postoperative ocular hypertension.

Effects of a topically applied 2% delta-9-tetrahydrocannabinol ophthalmic solution on intraocular pressure and aqueous humor flow rate in clinically normal dogs

OBJECTIVE To determine the effects of topically applied 2% delta-9-tetrahydrocannabinol (THC) ophthalmic solution on aqueous humor flow rate (AHFR) and intraocular pressure (IOP) in clinically normal dogs. ANIMALS 21 clinically normal dogs. PROCEDURES A randomized longitudinal crossover design was used. Following acquisition of baseline IOP (morning and evening) and AHFR (afternoon only) data, dogs were randomly assigned to 2 treatment groups and received 1 drop of either 2% THC solution or a control treatment (olive oil vehicle) to 1 randomly selected eye every 12 hours for 9 doses. The IOPs and AHFRs were reassessed after the final treatment. Following a washout period of ≥ 7 days, dogs were administered the alternate treatment in the same eye, and measurements were repeated. RESULTS Mean ± SD IOPs in the morning were 15.86 ± 2.48 mm Hg at baseline, 12.54 ± 3.18 mm Hg after THC treatment, and 13.88 ± 3.28 mm Hg after control treatment. Mean ± SD IOPs in the evening were 13.69 ± 3.36 mm Hg at baseline, 11.69 ± 3.94 mm Hg after THC treatment, and 12.13 ± 2.99 mm Hg after control treatment. Mean IOPs were significantly decreased from baseline after administration of THC solution but not the control treatment. Changes in IOP varied substantially among individual dogs. Mean ± SD AHFRs were not significantly different from baseline for either treatment. CONCLUSIONS AND CLINICAL RELEVANCE Topical application of 2% THC ophthalmic solution resulted in moderate reduction of mean IOP in clinically normal dogs. Further research is needed to determine efficacy in dogs with glaucoma.

Conjunctival xanthoma in a blue and gold macaw (Ara ararauna).

A 17-year-old female blue and gold macaw (Ara ararauna) presented for evaluation of a discreet, conjunctival mass of the OD. No other abnormalities were found on ophthalmic or physical examination. A heterophilic leukocytosis was present on the complete blood count, and elevated aspartate aminotransferase activity, creatinine kinase activity and cholesterol were present on the plasma biochemistry panel. Surgical removal of the mass was complete and no recurrence has occurred by six months after excision. Reduction of dietary fats was recommended to reduce serum cholesterol levels and reduce the likelihood of future occurrence of xanthomas in this bird.