Systemic absorption and gastrointestinal adverse effects from topical ketorolac and diclofenac ophthalmic solutions in healthy dogs

OBJECTIVE

To investigate systemic absorption and gastrointestinal (GI) adverse effects of topical ketorolac 0.5% and diclofenac 0.1% ophthalmic solutions.

ANIMALS

11 healthy purpose-bred Beagles.

METHODS

Dogs were randomly assigned to receive either ketorolac (n = 6) or diclofenac (5), 1 drop in both eyes 4 times daily for 28 days. Upper GI endoscopy was performed on days 0 and 29 with mucosal lesion scores (0 to 7) assigned to each region evaluated. Plasma samples were collected on days 14, 21, and 28 for measurement of diclofenac and ketorolac using high-performance liquid chromatography-mass spectrometry.

RESULTS

GI erosions and/or ulcers developed in all ketorolac-treated dogs and 1 of 5 diclofenac-treated dogs. Post-treatment mucosal lesion score for the antrum was higher in the ketorolac group than in the diclofenac group (P = .006) but not significantly different for any other region. Post-treatment antral mucosal lesion scores were significantly related to plasma ketorolac concentrations (P < .001). Ketorolac and diclofenac were detected in the plasma at all time points (median ketorolac day 14, 191 ng/mL; day 21, 173.5 ng/mL; and day 28, 179.5 ng/mL; and median diclofenac day 14, 21.1 ng/mL; day 21, 20.6 ng/mL; day 28, 27.5 ng/mL). Vomiting and decreased appetite events were observed uncommonly and were not significantly different between treatment groups.

CLINICAL RELEVANCE

GI ulceration and erosion developed after ophthalmic administration of ketorolac and diclofenac, with higher plasma concentrations and more severe GI lesions associated with ketorolac. Clients should be alerted to this potential risk with ophthalmic use and informed to watch for systemic clinical signs that would warrant veterinary reevaluation.

Incidence of concurrent systemic injuries with traumatic proptosis and its effect on outcome - 100 dogs

Objective

To evaluate the incidence of concurrent systemic injuries in dogs with traumatic ocular proptosis and their effect on survival to discharge. Additionally, to evaluate for associations between the type of trauma, each presenting vital signs, minimum laboratory database findings including packed cell volume, total solids, plasma glucose and lactate concentrations, and the diagnosis of concurrent systemic injury and survival.

Design

Retrospective study between the years 2017 and 2022.

Setting

One university teaching hospital and one large, private practice.

Animals

One hundred dogs presenting to the hospital with a diagnosis of traumatic ocular proptosis.

Measurements and main results

Medical records were retrospectively reviewed; signalment, breed, sex, age, weight, date of presentation, type of trauma sustained, time from trauma to presentation, vitals on presentation, and minimum laboratory database findings including packed cell volume (PCV), total solids (TS), plasma glucose concentration, and plasma lactate concentration were recorded. A modified animal trauma triage (ATT) score was retrospectively calculated. A total of 17 dogs (17%) had concurrent systemic injury. Compared to dogs without systemic injuries, dogs with systemic injuries had a significantly lower body temperature [median 101.1F (38.3C) vs. 101.6F (38.6C); P = 0.008], significantly higher plasma glucose concentrations (125 mg/dL, 6.9 mmol/L vs. 112 mg/dL, 6.2 mmol/L; P = 0.012) and approaching statistical significance, lower PCV values (median 40 vs. 46%; P = 0.051).

Conclusions

Dogs presenting with traumatic ocular proptosis do present with concurrent systemic, non-ocular injuries; however, these concurrent injuries do not seem to be associated with survival to discharge.

Retrospective evaluation of the incidence of gastrointestinal bleeding in dogs receiving ophthalmic nonsteroidal anti-inflammatory drugs

OBJECTIVES

To report the incidence of gastrointestinal (GI) bleeding and associated risk factors in a population of dogs receiving ophthalmic nonsteroidal anti-inflammatory drugs (NSAIDs).

ANIMAL STUDIED

Medical records of dogs prescribed ophthalmic NSAIDs (cases), dogs receiving systemic NSAIDs alone and dogs receiving systemic prednisone alone (controls).

PROCEDURES

Data were collected retrospectively from the medical records of 204 dogs prescribed ophthalmic NSAIDs (diclofenac, ketorolac, or flurbiprofen), which were subdivided based on if they received any concurrent systemic NSAIDs or glucocorticoids, 136 dogs receiving a systemic NSAID (carprofen or meloxicam) alone, and 151 dogs receiving a systemic glucocorticoid (prednisone) alone at a referral hospital from 2015 to 2019.

RESULTS

Gastrointestinal bleeds developed in 8/79 (10.1%) of topical NSAID-only cases, 10/136 (7.4%) of systemic NSAID controls, and 14/151 (9.3%) of systemic glucocorticoid controls, with no significant difference between the three groups (p = .6103). There were no significant differences in GI bleed rates between cases treated with ketorolac, diclofenac, or flurbiprofen (p = .160), although severe GI bleeding was only seen in ketorolac-treated dogs. Presence of a known concurrent risk factor for GI bleeding was significantly associated with the development of GI bleed in dogs on ophthalmic NSAIDs (p = .032).

CONCLUSIONS

Dogs treated with ophthalmic NSAIDs developed GI bleeding at a frequency comparable to dogs receiving systemic NSAIDs or systemic glucocorticoids alone, suggesting that dogs receiving ophthalmic NSAIDs may be at increased risk of GI bleeding.

Increased drug concentration and repeated eye drop administration as strategies to optimize topical drug delivery: A fluorophotometric study in healthy dogs

OBJECTIVES

Determine tear film kinetics with different fluorescein concentrations and repeated eye drop administration at various time intervals.

ANIMALS STUDIED

Six healthy Beagles.

PROCEDURES

Six experiments were conducted on separate days: single eye drop administration (control) or two separate eye drops administered at 30 s, 1, 2, 5, and 10 min intervals. For each experiment, one eye received 0.3% fluorescein solution while the other eye received 1% fluorescein solution, and tear fluid was collected with capillary tubes at 0, 1, 5, 10, 20, 30, 40, 50, 60, 90, 120, and 180 min. Fluorescein concentrations were measured using automated fluorophotometry.

RESULTS

Compared with 0.3% solution, eyes receiving 1% fluorescein solution had significantly higher tear film concentrations (p ≤ .046) and the area-under-the-fluorescein-time curve was twofold greater (p = .005). Compared with control: (i) Tear film concentrations were significantly higher for up to 20 min when repeating administration 30 s to 5 min after the first drop (p ≤ .006); (ii) The highest increase in area-under-the-curve was obtained with 2 and 5 min intervals for 0.3% (+109%-130%) and 1% solutions (+153%-157%); (iii) The highest increase in median precorneal retention time (defined as tear film concentration < 5% from baseline values) was obtained with 5 min intervals for 0.3% (55 min vs. 15 min in control) and 2-5 min intervals for 1% solutions (50 min vs. 25 min in control).

CONCLUSIONS

Drug delivery to the ocular surface can be enhanced by using more concentrated formulations and/or by repeating eye drop administration 2-5 min after the first dose.

Precorneal retention time of ocular lubricants measured with fluorophotometry in healthy dogs

OBJECTIVE

Determine the precorneal retention time of five different ocular lubricants commonly used in dogs.

ANIMALS STUDIED

Six healthy Beagle dogs (n = 12 eyes).

PROCEDURES

Five ocular lubricants were studied: Artificial Tears Solution® (1.4% polyvinyl alcohol), I-Drop® Vet Plus (0.25% hyaluronate), Optixcare® Eye Lube Plus (0.25% hyaluronate), Systane® Ultra (0.4% polyethylene glycol 400 and 0.3% propylene glycol), and Artificial Tears Ointment® (mineral oil/white petrolatum). Each lubricant was mixed with 10% sodium fluorescein to achieve 1% fluorescein formulations. Following topical administration of 35 mg in each eye, tear fluid was collected with capillary tubes at selected times (0, 1, 5, 10, 20, 30, 40, 50, 60, 90, 120, 180 min) and fluorescein concentrations were measured with a computerized scanning ocular fluorophotometer.

RESULTS

Tear fluorescence was significantly greater with Artificial Tears Ointment® compared with other lubricant formulations from 1 to 20 min post-administration. Median (range) precorneal retention times were significantly different among the 5 lubricants, ranging from 40 minutes (20-90 min) for Artificial Tears Ointment®, 35 min (20-90 min) for Systane® Ultra, 30 min (10-60 min) for I-Drop® Vet Plus, 25 min (10-60 min) for Optixcare® Eye Lube Plus, and 10 min (10-20 min) for Artificial Tears Solution®. Precorneal retention time was significantly lower for Artificial Tears Solution® compared with the other 4 formulations.

CONCLUSIONS

This study established normative data for the retention time of common lubricants on the ocular surface of dogs, which may be used to guide clinicians with their choice of lubricant and frequency of administration.

Impact of multi-drug resistance on clinical outcomes of dogs with corneal ulcers infected with Staphylococcus pseudintermedius

Objective

Compare characteristics and clinical outcomes of dogs with infectious keratitis from Staphylococcus pseudintermedius considered to be multidrug-resistant (MDR) or not.

Procedures

Staphylococcus pseudintermedius isolated as the primary pathogen from canine patients with ulcerative keratitis were considered MDR if resistant to at least one agent in three or more classes of antibiotics. Medical records were reviewed for history, patients' characteristics, clinical appearance, therapeutic interventions, and clinical outcomes.

Results

Twenty-eight dogs (28 eyes) were included. Compared to non-MDR cases, MDR diagnosis was significantly more common in dogs with recent (≤30 days) anesthesia (7/15 vs. 1/13, P = 0.038) and more common in non-brachycephalic dogs (8/15 vs. 2/13, P = 0.055). Clinical appearance (ulcer size/depth, anterior chamber reaction, etc.) did not differ significantly between groups (P ≥ 0.055). Median (range) time to re-epithelialization was longer in MDR vs. non-MDR eyes [29 (10-47) vs. 22 (7-42) days] but the difference was not significant (P = 0.301). Follow-up time was significantly longer in dogs with MDR keratitis [47 (29-590) vs. 29 (13-148) days, P = 0.009]. No other significant differences were noted between MDR and non-MDR eyes in regard to time for ulcer stabilization [4 (1-17) days vs. 4 (1-12), P = 0.699], number of eyes requiring surgical stabilization (7/15 vs. 7/13, P = 0.246) or enucleation (1/15 vs. 2/13, P = 1.000), success in maintaining globe (14/15 vs. 11/13, P = 0.583) or success in maintaining vision (12/15 vs. 10/13, P = 1.000).

Conclusions

MDR infections may prolong corneal healing time but did not appear to affect overall clinical outcomes in dogs with bacterial keratitis. Further research is warranted in a larger canine population and other bacterial species.

Culture and characterization of canine and feline corneal epithelial organoids: A new tool for the study and treatment of corneal diseases

In this study, we isolated and cultured canine and feline 3D corneal organoids. Samples derived from corneal limbal epithelium from one canine and one feline patient were obtained by enucleation after euthanasia. Stem cell isolation and organoid culture were performed by culturing organoids in Matrigel. Organoids were subsequently embedded in paraffin for further characterization. The expression of key corneal epithelial and stromal cell markers in canine and feline organoids was evaluated at the mRNA level by RNA-ISH and at the protein level by immunofluorescence (IF) and immunohistochemistry (IHC), while histochemical analysis was performed on both tissues and organoids using periodic-acid Schiff (PAS), Sirius Red, Gomori's Trichrome, and Colloidal Iron stains. IF showed consistent expression of AQP1 within canine and feline organoids and tissues. P63 was present in canine tissues, canine organoids, and feline tissues, but not in feline organoids. Results from IHC staining further confirmed the primarily epithelial origin of the organoids. Canine and feline 3D corneal organoids can successfully be cultured and maintained and express epithelial and stem cell progenitor markers typical of the cornea. This novel in vitro model can be used in veterinary ophthalmology disease modeling, corneal drug testing, and regenerative medicine.

Kinetics and minimal inhibitory concentrations of ceftiofur in tear film following extended-release parenteral administration (Excede®) in dogs

Purpose

Describe the pharmacokinetics of extended-release parenteral ceftiofur (Excede^®) in canine tear film and compare these concentrations to minimal inhibitory concentrations (MICs) of ceftiofur against common ocular pathogens in dogs.

Method

Six dogs of various breeds were enrolled. Disruption of blood-tear barrier was achieved with histamine-induced conjunctivitis to ensure clinical relevance of the results. Each dog received a single subcutaneous injection of 5 mg/kg Excede^®, followed by tear collection with Schirmer strips at times 0, 0.25, 0.5, 1, 2, 4, 8, 12, 24, 36, 48, 72, 96, 120, 144, 168, 192, 216 and 240 h. Drug quantification was performed with liquid chromatography-mass spectrometry. MICs were determined for Staphylococcus pseudintermedius, Streptococcus canis and Pseudomonas aeruginosa by assessing bacterial growth (n = 10 per bacterial species) in the presence of ceftiofur at increasing concentrations.

Results

Blood-tear barrier breakdown provided tear film concentrations of ceftiofur 3.2–28.9-fold higher than in the contralateral healthy eye (n = 1 dog, pilot experiment). In all six dogs, ceftiofur concentrations in tears varied from 2.3 to 637.5 ng/mL and were detectable up to 10 days (240 h) after subcutaneous injection. However, tear levels always remained below MICs for common ocular isolates (≥640 ng/mL).

Conclusions

Ceftiofur reached the tear compartment (for up to 10 days) after a single parenteral injection, however tear concentrations were extremely variable and too low to be effective against common bacterial pathogens in dogs. Further studies with different ceftiofur dosage or other long-acting injectable antibiotics are warranted.

Variable accuracy, precision, and consistency of compounded famciclovir formulated for management of feline herpesvirus-1 in cats

OBJECTIVE

To evaluate compounded famciclovir suspensions for accuracy, precision, and consistency in drug content.

PROCEDURES

Two compounded famciclovir concentrations were evaluated (250 and 400 mg/mL, 30 preparations total from nine 503A compounding pharmacies) with U.S. Food and Drug Administration (FDA)-approved famciclovir tablets as control. Drug quantification via high-performance liquid chromatography (with famciclovir reference standard and pramipexole internal standard) was performed at 0, 14, and 28 days with concentrations of 90%-110% of labeled dose considered acceptable (US Pharmacopoeia standards).

RESULTS

FDA-approved tablets from three different manufacturers were found to be accurate and precise with acceptable drug content. A significantly greater mean deviation from labeled content was noted for 400 mg/mL suspensions (-52.9%) compared to 250 mg/mL suspensions (-18.0%). When assessing time points separately, 15/63 (24%) samples of 250 mg/mL and 0/27 (0%) samples of 400 mg/mL suspensions met the acceptance standards. Coefficients of variation (CV) in drug content among pharmacy batches ranged from 0.5% to 29%, with 5/10 formulations having significantly lower CV% compared to control (decreased precision). Similarly, drug content changed over time (0-28 days) in all compounded formulations, with both downward and upward trends observed (variable consistency).

CONCLUSIONS

Most compounded famciclovir formulations were inaccurate, imprecise, and inconsistent. FDA-approved famciclovir tablets may be preferred over compounded famciclovir formulations for the management of feline herpesvirus-1. If compounded famciclovir is used in practice, a concentration of 250 mg/mL is preferred over 400 mg/mL given the lower accuracy of the higher concentration.

Novel use of a combination of extracellular matrices for wound healing following resection of a large inferior eyelid mass in a miniature Hereford

CASE DESCRIPTION

A 9-month-old miniature Hereford heifer was evaluated for a mass on the right inferior eyelid that had progressed in size over 3 months.

CLINICAL FINDINGS

Physical examination revealed a firm, ulcerated, pedunculated mass on the right inferior eyelid that extended from the medial quarter to beyond the lateral canthus of the eye. The base of the mass measured 7.4 × 6.7 cm, and the dorsal margin of the base of the mass was approximately 3 mm ventral to the inferior eyelid margin. Histologic evaluation of incisional biopsy specimens from the mass was consistent with fibrosarcoma.

TREATMENT AND OUTCOME

The mass was surgically resected with care taken to preserve the eyelid margin. The resulting 10 × 8.5-cm surgical wound was treated with adjunct CO₂ laser therapy and closed by primary closure at its medial and central aspects and placement of a 4.6 × 2.6-cm lyophilized equine amnion multilayer graft and 2 sheets of 4-ply porcine small intestinal submucosa at its lateral aspect. The grafts were kept moist by alternating topical antimicrobial and artificial tear ointments for 3 weeks. The wound healed without complications, resulting in a functional and aesthetically pleasing outcome despite the development of moderate ectropion at the lateral aspect of the inferior eyelid.

CLINICAL RELEVANCE

Results suggested that a combination of extracellular matrix scaffolds may be an alternative to extensive skin flaps for management of large dermal wounds, particularly wounds resulting from blepharoplasty where preservation of an eyelid margin is desired.

Influence of Schirmer strip wetness on volume absorbed, volume recovered, and total protein content in canine tears

OBJECTIVE

Determine the protein content and volume of tears sampled by Schirmer strips wetness ranging from 20 to 35 mm.

ANIMALS STUDIED

Ten healthy beagle dogs.

PROCEDURES

Each dog underwent 20 tear collections per day (10 sessions in each eye, spaced by ≥1 h) for 4 separate days, providing 200 tear samples for each length of wetness evaluated: 20, 25, 30, and 35 mm. A Schirmer strip was placed in each eye until the selected mm-mark was reached, calculating the volume absorbed (VA) as the difference between the post- and pre-collection weight (assuming 1 mg~1 µL for tear fluid), and the volume recovered (VR) as the amount pipetted from the tube following centrifugation. Total protein content (TPC) was measured with infrared spectroscopy. Outcome measures were compared with the Kruskal-Wallis test.

RESULTS

Median values for VA (µL), VR (µL) and TPC (mg/mL) were as follows: 20 mm (18, 10, 5.94), 25 mm (22, 12.5, 5.97), 30 mm (25.5, 16, 5.89), and 35 mm (31, 22.5, 7.13). Both VA and VR were significantly greater (p < .001) for Schirmer strips wetness of 35»30»25»20 mm. TPC was significantly greater (p < .001) for 35 > 20-30 mm, but not among other groups (p = 1.000).

CONCLUSIONS

The study established normative data to consider when canine studies use Schirmer strips to collect tears for bioanalytical purposes (eg, proteomics, pharmacokinetics). Although 35 mm yielded higher VA and VR, the higher TPC could be explained by greater disruption of ocular surface homeostasis. Absorption to 20-30 mm is the suggested length of strip wetness for bioanalytical tear collection in dogs.

Case Report: Successful Management of Refractory Keratomycosis in an Alpaca Using Penetrating Keratoplasty and Combination Antifungal Therapy (Caspofungin 0.5% and Terbinafine 1%)

Fungal keratitis is a common disease in certain parts of the world and affects several species, including equids, camelids, and homo sapiens, leading to blindness or loss of the eye if the infection is not adequately controlled. Reports of clinical use of antifungals caspofungin and terbinafine are limited across both veterinary and human medical literature. The alpaca presented in this case demonstrates that deep keratomycosis can be caused by Scopulariopsis brevicaulis and Fusarium verticillioides, two previously unreported fungi to cause keratomycosis in camelids. This report demonstrates successful management with a combination of surgery and topical ophthalmic treatment with caspofungin 0.5% solution and terbinafine 1% dermatologic cream, after initially failing treatment with topical voriconazole 1% solution. Combination therapy appears more effective than monotherapy with some fungal organisms, and synergy between antifungal agents is thought to play a role in the success of combination therapy. Surgery to remove the bulk of the fungal infection is especially helpful in cases that fail initial medical therapy.

Bacterial Cross-Contamination in a Veterinary Ophthalmology Setting

The present study describes the prevalence of bacterial cross-contamination in a veterinary ophthalmology setting, a serious issue that can result in healthcare-associated (or nosocomial) infections among patients and staff. Retrospective (n = 5 patients) and prospective (n = 23 patients) studies evaluated bacterial isolates in companion animals presenting with ulcerative keratitis, sampling the patients' cornea and surrounding examination room, including the environment (exam table, countertop, floor) and ophthalmic equipment (slit lamp, transilluminator, direct ophthalmoscope, indirect headset, tonometer). Results of bacterial culture and antibiotic susceptibility testing were recorded, and degree of genetic relatedness was evaluated in six pairs of isolates (cornea + environment or equipment) using pulse-field gel electrophoresis (PFGE). Overall contamination rate of ophthalmic equipment, environment, and examination rooms (equipment + environment) was 42.9% (15/35 samples), 23.7% (9/38 samples) and 32.9% (24/73 samples), respectively. Methicillin-resistant Staphylococcus pseudintermedius (MRSP), a multi-drug resistant (MDR) pathogen with zoonotic potential, was isolated in 8.2% (6/73) of samples. The patient's cornea was likely the source of cross-contamination in 50% (3/6) of MRSP pairs as evaluated by PFGE; notably, two of the three similar bacterial strains did not have an exact match of their antibiotic susceptibility profiles, highlighting the importance of advanced diagnostics such as PFGE to assess cross-contamination in healthcare facilities. Future work could examine the contamination prevalence of specific equipment or the efficacy of cleaning protocols to mitigate cross-contamination in veterinary practice.

Histologic effects of MicroPulse™ transscleral cyclophotocoagulation in normal equine eyes

OBJECTIVE

Determine the immediate post-operative effects of MicroPulse^™ transscleral cyclophotocoagulation (MP-TSCPC) in healthy equine eyes.

ANIMALS STUDIED

Ten adult horses.

METHODS

MP-TSCPC was performed on sedated horses in 12 eyes (4 groups) using the following parameters (power, duration, duty cycle): (1) 2000 mW, 180 seconds, 31.3%; (2) 3000 mW, 180 seconds, 31.3%; (3) 3000 mW, 270 seconds, 31.3%; and (4) 3000 mW, 270 seconds, 50%. Three additional eyes were left untreated (control). Eyes were monitored clinically until euthanasia (mean = 3 hours post-procedure). Histologic sections were assessed with light microscopy and transmission electron microscopy (TEM).

RESULTS

MP-TSCPC was well tolerated by sedated horses. Adverse effects were only noted in Group 4: ocular hypertension (n = 3/3), conjunctival burns (3/3), aqueous flare (2/3), and a corneal erosion (1/3). Histologic scoring of Group 4 was statistically greater than other treated groups (1-3) and control eyes (P ≤ .021). TEM showed subtle changes to the mitochondria and plasma membrane infoldings of the basilar surface of the nonpigmented epithelium in all treated eyes.

CONCLUSIONS

MP-TSCPC does not cause immediate post-procedure adverse clinical effects or pronounced morphological changes to the ciliary body, except with the highest laser settings evaluated (power 3000 mW, duration 270 seconds, duty cycle 50%).

Prevalence and Antibiotic Susceptibility of Bacterial Isolates From Dogs With Ulcerative Keratitis in Midwestern United States

The objective of this study was to describe bacterial culture and antibiotic susceptibility results in 476 dogs presenting with suspected bacterial keratitis in Iowa and surrounding Midwestern states, further detailing trends in patient characteristics, seasonality, and antimicrobial resistance. Corneal swabs yielded 465 bacterial isolates and 220 cultures (46.2%) with no apparent growth (0–5 isolates per culture). The most frequent bacterial genera were Staphylococcus (32.3%), Streptococcus (19.1%), and Pseudomonas (12.5%), while the most common bacterial species were Staphylococcus pseudintermedius (26.7%), Streptococcus canis (12%), and Pseudomonas aeruginosa (7.5%). Compared to mixed-breed dogs, canine breeds most likely to be examined for ulcerative keratitis included Boston terrier, Cavalier King Charles spaniel, miniature pinscher, pug, rat terrier, Saint Bernard, shih tzu, and silky terriers. In summer, the likelihood to yield a negative culture was reduced while the likelihood to culture Pseudomonas species was increased. Bacteria considered multidrug resistant (MDR, resistant to ≥ 3 antibiotic classes) represented 20% of all canine isolates and were most prevalent for Staphylococcus species (33%). An alarming, escalating trend of MDR prevalence was noted between 2016 (5%) and 2020 (34%). Individual ophthalmic preparations (i.e., single antibiotics or commercially available antibiotic combinations) with highest efficacy against all bacterial isolates included chloramphenicol (83%), ceftiofur (79%), amikacin (77%), neomycin-polymyxin B-bacitracin (77%), and gentamicin (74%). Efficacy of systemic antibiotics and combinations of ophthalmic preparations was also evaluated. Based on the present findings, triple antibiotic (Neo-Poly-Bac) is recommended as empirical monotherapy for prophylactic antibiotic therapy in dogs with simple corneal ulcers, while a chloramphenicol-ciprofloxacin combination is empirically recommended for therapeutic management of infected corneal ulcers. Pending culture and susceptibility results, appropriate selection of empiric antibiotic therapy is important to enhance therapeutic outcome and reduce antibacterial resistance in dogs with corneal ulceration.

Impact of diurnal variation, sex, tear collection method, and disease state on tear protein levels in dogs

OBJECTIVE

To investigate the effects of various biological factors on total protein concentration (TPC) and serum albumin levels in canine tears.

ANIMALS STUDIED

10 healthy beagles (5 female, 5 male) were used.

PROCEDURES

Experiments were conducted on separate days, collecting tears with either capillary tubes or Schirmer strips, as follows: (i) Tear collection at 3 hours intervals (from 6 am to 12 am); and (ii) Tear collection before and 20 minutes following topical histamine application (1, 10, 375 mg/mL) to induce mild, moderate, and severe conjunctivitis, respectively. TPC and serum albumin were measured with infrared spectroscopy and ELISA, respectively.

RESULTS

Tear film TPC and serum albumin ranged from 9.7-26.1 mg/mL and 6.4-1662.6 µg/mL, respectively. Protein levels did not differ significantly among time points (P ≥ .080). Median coefficient of variation (CV%) was lower with Schirmer strips compared to capillary tubes for both TPC (12% vs 15%, P = .020) and serum albumin (57% vs 78%, P = .232). TPC (P < .001), but not serum albumin was greater in male vs. female dogs. Serum albumin, but not TPC (P ≥ .099), increased significantly with each grade of conjunctivitis severity (P < .001), with no differences between collection devices (P ≥ .322); median increase was 106%, 1389%, and 2871% in eyes with mild, moderate, and severe conjunctivitis, respectively.

CONCLUSIONS

There is no apparent diurnal variation in canine tear protein levels. Blood-tear barrier breakdown with conjunctivitis allows serum albumin to leak into the tear film at high concentrations. Schirmer strips compare well with capillary tubes for bioanalytical purposes in healthy and diseased eyes, and this collection method may offer improved reproducibility for protein quantification.

Serum albumin and total protein concentration in the tear film of horses with healthy or diseased eyes

OBJECTIVE

To determine total protein content (TPC) and serum albumin levels in the tears of horses with healthy or diseased eyes.

ANIMALS STUDIED

Forty-two horses with healthy eyes and 11 horses with unilateral (n = 10) or bilateral (n = 1) ocular disease.

PROCEDURE

Each eye underwent an ophthalmic examination including detailed conjunctivitis scoring and tear collection with Schirmer strips. TPC and serum albumin levels were quantified in tear samples and compared among healthy eyes, affected eyes, and contralateral unaffected eyes. The impact of the following variables on lacrimal protein levels were assessed: age, breed, and sex (healthy eyes), as well as conjunctivitis score (diseased eyes).

RESULTS

Lacrimal TPC ranged from 7.0 to 19.5 mg/mL in healthy eyes, while serum albumin ranged from 71.1 to 711.3 µg/mL (~1.6% of TPC) and was higher in tears of aged and female horses (P ≤ .033). Eyes with ocular disease had significantly greater (P ≤ .001) serum albumin in tears (median 679.6 µg/mL) compared to contralateral unaffected eyes (130.0 µg/mL) and eyes of the reference population (200.7 µg/mL). However, lacrimal TPC did not differ significantly among the 3 groups. Scoring of palpebral conjunctival hyperemia trended toward a positive association with serum albumin in tears (r = 0.49, P = .062).

CONCLUSIONS

The protein profile in equine tears differs in health and disease. Serum albumin in tears increases with ocular disease and, similar to other species, might serve as a biomarker for ocular insult in horses. Future studies could investigate the protein levels in horses with specific ocular conditions and help determine the biological importance of albumin on the equine ocular surface.

Impact of acute conjunctivitis on ocular surface homeostasis in dogs

OBJECTIVE

To investigate the effects of acute conjunctivitis on tear film characteristics and corneal sensitivity in dogs.

ANIMALS STUDIED

Eight female spayed Beagle dogs (1.5-2 years old, 7.5-10 kg).

PROCEDURES

On two consecutive days, one randomly selected eye in each dog received 1 or 375 mg/mL histamine solution to induce mild or severe conjunctivitis, while the contralateral eye served as control. Diagnostic tests were performed in the following order: fluorescein instillation and repeated tear collection over 20 minutes (to determine tear volume [TV] and turnover rate [TTR] by fluorophotometry), Schirmer tear test-1 (STT-1), tear ferning, corneal esthesiometry, and tear film breakup time (TFBUT).

RESULTS

Results are presented as median values for severe conjunctivitis, mild conjunctivitis, and control eyes. Eyes with severe conjunctivitis had significantly higher STT-1 (24, 19.5, 17.5 mm/min; P = .002) and significantly lower TFBUT (10.5, 13.5, 15.5 s; P = .002), but no changes were noted in corneal tactile sensation (2, 2.5, 2.5 cm) or tear ferning (grades 2, 2, 2.5). Severe conjunctivitis significantly increased TV by nearly 10-fold (631, 97, 65 µL) initially (reflex tearing), although basal TV returned rapidly (<5 minutes) in all eyes (46, 58, 48 µL). Finally, there was a nonsignificant trend for higher reflex TTR in the conjunctivitis vs control eyes (68, 58, 43%/min).

CONCLUSIONS

Experimentally induced conjunctivitis increases tear quantity and decreases tear quality in dogs, but has no impact on corneal sensitivity. Changes in tear film dynamics could affect ocular pharmacology (eg, precorneal retention time), although homeostasis of lacrimal volume and drainage is rapidly restored.

Comparison of topically administered 0.05% difluprednate and 1% prednisolone acetate for inhibition of aqueocentesis-induced breakdown of the blood-aqueous barrier in healthy dogs

OBJECTIVE

To compare the efficacy of 0.05% difluprednate ophthalmic emulsion and 1% prednisolone acetate ophthalmic suspension for controlling aqueocentesis-induced breakdown of the blood-aqueous barrier in healthy dogs.

ANIMALS

34 healthy dogs.

PROCEDURES

Dogs were allocated to 5 groups (6 to 8 dogs/group) to receive 0.05% difluprednate, 1% prednisolone acetate, or saline (0.9% NaCl) solution (control treatment) in both eyes 2 or 4 times daily. Eye drops were administered topically for 5 consecutive days. Anterior chamber paracentesis (aqueocentesis) was performed in 1 eye on the third day. Automated fluorophotometry was performed immediately before and 20 minutes and 24 and 48 hours after aqueocentesis. Relative fluorescence (RF), defined as fluorescence of the eye that had undergone aqueocentesis divided by fluorescence of the contralateral eye, was calculated to help control for variation among dogs.

RESULTS

Mean RF was significantly lower at 24 hours after aqueocentesis in dogs treated twice daily with 0.05% difluprednate or 4 times daily with 1% prednisolone acetate than in dogs receiving the control treatment. At 48 hours after aqueocentesis, mean RF was significantly lower in dogs treated 4 times daily with 1% prednisolone acetate than in control dogs. Mean RF differed over time in dogs treated 4 times daily with 0.05% difluprednate but did not differ over time for any of the other treatments.

CONCLUSIONS AND CLINICAL RELEVANCE

All 4 treatments were effective for reducing aqueocentesis-induced anterior uveitis in healthy dogs regardless of the drug or frequency of administration. Topical ophthalmic administration of 0.05% difluprednate may be a viable treatment option for dogs with anterior uveitis and warrants further study.

Kinetics of Fluorescein in Tear Film After Eye Drop Instillation in Beagle Dogs: Does Size Really Matter?

The study aimed to determine the impact of drop size on tear film pharmacokinetics and assess important physiological parameters associated with ocular drug delivery in dogs. Two separate experiments were conducted in eight healthy Beagle dogs: (i) Instillation of one drop (35 μl) or two drops (70 μl) of 1% fluorescein solution in each eye followed by tear collections with capillary tubes from 0 to 180 min; (ii) Instillation of 10 to 100 μl of 0.1% fluorescein in each eye followed by external photography with blue excitation filter (to capture periocular spillage of fluorescein) and tear collections from 1 to 20 min (to capture tear turnover rate; TTR). Fluorescein concentrations were measured in tear samples with a fluorophotometer. The TTR was estimated based upon non-linear mixed-effects analysis of fluorescein decay curves. Tear film pharmacokinetics were not superior with instillation of two drops vs. one drop based on tear film concentrations, residual tear fluorescence, and area under the fluorescein-time curves (P ≥ 0.163). Reflex TTR varied from 20.2 to 30.5%/min and did not differ significantly (P = 0.935) among volumes instilled (10-100 μl). The volumetric capacity of the canine palpebral fissure (31.3 ± 8.9 μl) was positively correlated with the palpebral fissure length (P = 0.023). Excess solution was spilled over the periocular skin in a volume-dependent manner, predominantly in the lower eyelid, medial canthus and lateral canthus. In sum, a single drop is sufficient for topical administration in dogs. Any excess is lost predominantly by spillage over the periocular skin as well as accelerated nasolacrimal drainage.

Nerve growth factor in dogs: Assessment of two immunoassays and selected ocular parameters following a nicergoline challenge per os

Impairment of corneal nerves can result in the development of ocular surface diseases such as aqueous tear deficiency and neurotrophic keratopathy. This study investigates oral nicergoline, an α-adrenoceptor antagonist shown to enhance endogenous secretion of nerve growth factor (NGF) by the lacrimal gland, as a potential therapy for these conditions. Five female spayed Beagle dogs received a 2-week course of oral nicergoline (10 mg twice daily). Drug safety was evaluated with ophthalmic and physical examinations, blood pressure monitoring, bloodwork, and urinalysis. The effect of nicergoline on the ocular surface was assessed with corneal esthesiometry, Schirmer tear test-1, and tear film breakup time. Drug effect on NGF levels was assessed by collecting tears and blood at baseline and completion of therapy using a bead-based immunoassay and an enzyme-linked immunosorbent assay. Although nicergoline was well tolerated in all dogs, it did not have a significant impact on corneal sensitivity, tear production, or tear stability. Of note, NGF was below the limit of quantification in all tear samples and was only detected in 8/20 serum samples with no significant difference between levels at baseline (189.4 ± 145.1 pg/mL) and completion of therapy (149.4 ± 79.4 pg/mL). Further validation of NGF analytical assays is warranted before nicergoline is investigated in clinical patients.

Fluorophotometric Assessment of Tear Volume and Turnover Rate in Healthy Dogs and Cats

Purpose: The study establishes normative data of tear volume (TV) and tear turnover rate (TTR) in healthy dogs and cats, 2 species commonly used for translational research in ophthalmology.

Methods: Thirty-six dogs and 24 cats were enrolled, encompassing a variety of breeds with diverse skull conformations (brachycephalic, mesocephalic, and dolichocephalic). Two microliters of 10% fluorescein were instilled onto the upper bulbar conjunctiva of both eyes, followed by tear collection with 2-μL capillary tubes at 0, 2, 4, 6, 10, 15, and 20 min. Fluorescein concentrations were measured with a computerized scanning ocular fluorophotometer. The TV and TTR were estimated based upon nonlinear mixed-effects analysis of fluorescein decay curves.

Results: In dogs, median (interquartile range) TV, basal TTR (bTTR), and reflex TTR (rTTR) were 65.3 μL (42.3–87.9), 12.2%/min (3.7–22.1), and 50.0%/min (25.9–172.3), respectively. In cats, median (interquartile range) TV, bTTR, and rTTR were 32.1 μL (29.5–39.9), 10.9%/min (3.0–23.7), and 50.0%/min (28.4–89.4), respectively. Body weight (r = 0.44) and age (r = 0.30) were positively correlated (P ≤ 0.019) with TV in dogs. Age was negatively correlated (P ≤ 0.018) with TTR in dogs (r = −0.33) and cats (r = −0.24). However, TV and TTR were not associated with skull conformation in either species.

Conclusions: Dogs have greater TV than cats but similar basal and rTTR. Tear parameters were impacted by body weight and age, but not by skull conformation. In both clinical and research settings, successive lacrimal tests should be spaced by ≥10 min to provide sufficient time for the tear film to replenish, as bTTR is ∼11%/min–12%/min in both species.

Histamine-Induced Conjunctivitis and Breakdown of Blood-Tear Barrier in Dogs: A Model for Ocular Pharmacology and Therapeutics

Conjunctival inflammation disturbs the blood–tear barrier and thus affects the tear film stability and composition. We aimed to develop a non-invasive and reliable method to induce conjunctivitis in dogs, a large animal model for translational work on ocular surface disease in humans. Six beagle dogs underwent a randomized, vehicle-controlled, balanced crossover trial—on six separate days, one eye received topical artificial tears (vehicle), while the other eye received one of six concentrations of histamine solution (0.005–500 mg/ml). At sequential times after eyedrop administration, a conjunctivitis score was given to each eye based on the degree of palpebral and bulbar conjunctival hyperemia and chemosis, ocular pruritus, and discharge. Total protein content (TPC) and serum albumin were quantified in tear fluid at baseline and 20 min. Additionally, 13 dogs presenting for various ophthalmic diseases with associated conjunctivitis were examined. Experimentally induced conjunctivitis developed rapidly (<1 min) following topical histamine administration and lasted for 1–3 h (four lowest doses) to 6–8 h (two highest doses). The severity of conjunctivitis was dose-dependent. Histamine was overall well tolerated, although transient blepharitis, aqueous flare, and ocular hypertension occurred in a few dogs receiving histamine ≥375 mg/ml. TPC and serum albumin levels increased in tears of eyes receiving histamine ≥1.0 mg/ml, being significantly higher than vehicle and baseline in eyes receiving histamine ≥375 mg/ml. Lacrimal albumin levels were also increased in 13 dogs with naturally acquired conjunctivitis, up 2.7–14.9 fold compared to contralateral healthy eyes. Histamine-induced conjunctivitis represents a robust model for translational work on the ocular surface given the low cost, non-invasiveness, self-resolving nature, ability to adjust the duration and severity of the disease, and shared features with naturally occurring ocular diseases. Histamine solutions of 1, 10, and 375 mg/ml induce mild, moderate, and severe conjunctivitis in dogs, respectively. Leakage of serum albumin in tear fluid of eyes with conjunctivitis suggests a breakdown of the blood–tear barrier.

Tear Fluid Pharmacokinetics Following Oral Prednisone Administration in Dogs With and Without Conjunctivitis

Purpose: To describe the pharmacokinetics (PK) of prednisone and prednisolone in tear fluid of dogs receiving oral prednisone at anti-inflammatory to immunosuppressive doses and to assess the impact of induced conjunctivitis on lacrimal drug levels. Methods: Six healthy Beagle dogs were administered 4 courses of prednisone at 0.5, 1.0, 2.0, and 4.0 mg/kg given orally once a day for 5 days. At steady state, topical histamine was applied to induce mild (1 mg/mL) or severe (375 mg/mL) conjunctivitis in 1 eye of each dog and tear samples were collected from both eyes at selected times. Prednisone and prednisolone were quantified in tears by liquid chromatography-mass spectrometry. Results: Lacrimal prednisone and prednisolone concentrations ranged from 2 to 523 ng/mL and 5 to 191 ng/mL, respectively. Drug concentrations were overall greater in dogs receiving higher doses of prednisone, but were not correlated with tear flow rate. Eyes with conjunctivitis often had larger amounts of prednisone and prednisolone in tear fluid compared to control eyes (up to +64%), but differences were not statistically significant. Significantly greater, but clinically insignificant, levels of prednisolone were found in eyes with severe versus mild conjunctivitis for oral prednisone doses ≥1.0 mg/kg. Conclusions: Disruption of the blood-tear barrier with conjunctivitis did not significantly affect drug levels in tears. Based on drug PK in tears, oral prednisone is likely safe for the management of reflex uveitis and ocular surface diseases. However, further prospective trials using systemic corticotherapy in diseased animals are warranted to confirm findings from this preclinical study.

Evaluation of microbial contamination of canine plasma eyedropper bottles following clinical use in canine patients

OBJECTIVE

To investigate microbial contamination of canine plasma eye drops when used clinically and to compare the effect of two different eyedropper bottles on contamination rate.

METHODS

Forty-six bottles containing plasma were randomly dispensed for use on 42 dogs with ulcerative keratitis. Of these, 23 were standard eyedropper bottles and 23 were Novelia^® bottles designed to prevent contamination. After use for up to 2 weeks, samples for bacterial culture were obtained from a drop of plasma, the bottle tip, the plasma inside the bottle, and the corneal surface. Fungal culture was performed from a drop of plasma.

RESULTS

The overall microbial contamination rate was 17.4% (8/46 bottles); however, only one bottle had growth from the plasma inside the bottle. There was a lower contamination rate of Novelia^® bottles (3/23 = 13.0%) compared to standard bottles (5/23 = 21.7%), but this difference was not statistically significant (P = .57). There were also no significant differences in contamination rate of bottles used greater than 7 days compared to less than or equal to 7 days, or in bottles used greater than 4 times daily compared to 4 times daily or less. Three corneal samples (6.5%) had bacterial growth, but none matched contamination from the bottles.

CONCLUSIONS

Novelia^® bottles may decrease contamination of plasma eye drops used clinically. However, while microbial contamination of plasma bottles was documented, no clinically relevant complications were observed. This study supports safe use of plasma eye drops for up to 2 weeks when refrigerated and dispensed from either Novelia^® or standard eyedropper bottles.

Metastatic intraocular hemangiopericytoma in a dog

A 10-year-old Labrador Retriever who had been undergoing therapy for a recurrent hemangiopericytoma of the right flank presented to the Kansas State University Ophthalmology service for evaluation of a painful left eye. Examination revealed secondary glaucoma and irreversible blindness of the affected eye and multifocal chorioretinal lesions in the fellow eye. Therapeutic and diagnostic enucleation of the left eye was performed and histopathologic examination demonstrated the presence of a presumed metastatic spindle cell sarcoma. Further immunohistochemical staining confirmed the intraocular neoplasia to be metastatic spread from the previously removed flank mass. Rapid progression in size and number of chorioretinal lesions in the right eye was noted in the post-operative period until the patient was euthanized one month after surgery. This case report is the first to document intraocular metastasis of hemangiopericytoma in a veterinary patient.

Schirmer tear test I in dogs: results comparing placement in the ventral vs. dorsal conjunctival fornix

OBJECTIVE

To compare Schirmer tear test I (STT I) values obtained from placement of tear strips in the ventral and dorsal conjunctival fornices in dogs.

PROCEDURE

Schirmer tear test I was performed on each eye of 16 clinically normal dogs (32 eyes) in a crossover study. Initial tear strip placement site was randomized for each eye. Alternative placement site measurements were obtained after 1 week.

RESULTS

The mean (± standard deviation, SD) STT I for dorsal and ventral conjunctival fornices was 20.44 (±4.46) mm/min and 23.56 (±3.98) mm/min, respectively. STT I values obtained from the ventral conjunctival fornix were significantly greater than those obtained from the dorsal conjunctival fornix (P = 0.004).

CONCLUSIONS

Schirmer tear test I values were significantly greater with tear strips placed in the ventral conjunctival fornix.

Bioavailability and biochemical effects of diclofenac sodium 0.1% ophthalmic solution in the domestic chicken (Gallus gallus domesticus)

OBJECTIVE

To determine if topical ophthalmic diclofenac sodium 0.1% solution alters renal parameters in the domestic chicken, and to determine if the drug is detectable in plasma after topical ophthalmic administration.

ANIMALS

Thirty healthy domestic chickens.

PROCEDURES

Over 7 days, six birds were treated unilaterally with one drop of artificial tear solution (group 1), 12 birds were treated unilaterally (group 2) and 12 bilaterally (group 3) with diclofenac sodium 0.1% ophthalmic solution. Treatments were provided every 12 h in all groups. Pre- and post-treatment plasma samples from all birds were evaluated for changes in albumin, total protein, and uric acid. Post-treatment samples of all birds, collected 15 min post-administration, were analyzed by high-performance liquid chromatography with mass spectrometry for diclofenac sodium detection. A randomly selected renal sample from each group was submitted for histopathologic review.

RESULTS

Changes in pre- and post-treatment plasma albumin were significant (P < 0.05) in groups 2 and 3, but not for group 1. Pre- and post-treatment changes in total protein and uric acid were not significant for any group. Diclofenac sodium was not detectable (limit of detection = 0.10 ng/mL) in plasma samples from birds in group 1. Post-treatment concentration of diclofenac in group 3 was statistically greater than group 2 (P = 0.0008). Histopathologic changes did not identify diclofenac-induced acute renal tubular necrosis.

CONCLUSIONS

Ophthalmic diclofenac sodium 0.1% administered topically every 12 h in one or both eyes for 7 days is detectable in systemic circulation in the domestic chicken, but does not cause overt significant changes in plasma uric acid or total protein.

Retinal detachment postphacoemulsification in Bichon Frises: a retrospective study of 54 dogs

OBJECTIVE

To compare rates of retinal detachment (RD) postphacoemulsification in American Bichon Frises with and without prophylactic retinopexy.

PROCEDURES

Medical records of 54 Bichon Frises undergoing phacoemulsification with or without prophylactic retinopexy between 2003 and 2013 in one or both eyes were reviewed from five Midwestern university veterinary teaching hospitals. Inclusion criteria were preoperative ERG, at least 6 months of follow-up postphacoemulsification, and the absence of preexisting RD as determined by ophthalmic examination and/or ultrasound. Statistical analyses were performed using chi-squared test, and Wilcoxon rank-sum tests and Wilson confidence intervals with the P-value <0.05 were considered significant.

RESULTS

Phacoemulsification was performed without retinopexy in 79 eyes (42 dogs, non-PR group) and with prophylactic retinopexy in 23 eyes (12 dogs, PR group). Incidence of diabetes mellitus was 10/42 and 3/12 in the non-PR and the PR groups, respectively (P = 0.93). Intraocular lens implantation was performed in 40/42 non-PR dogs and 11/12 PR dogs (P = 0.63, 73/79 vs. 21/23 eyes). At final re-examination, RD occurred in 4/79 eyes without retinopexy, compared to 0/23 RD in the retinopexy group. There was no statistically significant difference in RD rates between the two groups (P = 0.27).

CONCLUSIONS

These data provide no statistical evidence to support prophylactic retinopexy in Bichon Frises. Due to the low rate of retinal detachment following phacoemulsification without prophylactic retinopexy, the procedure appears to offer limited benefit to offset cost, procedural risk, and risk of extended or repeated anesthesia in Bichon Frises.

A pulse-dose topical 1% 5-fluorouracil treatment regimen in a young dog with corneal squamous cell carcinoma

PURPOSE

To describe the use of a pulse-dose topical 5-fluorouracil (5-FU) treatment regimen in a Pug dog with corneal squamous cell carcinoma (SCC).

METHODS

A 1-year-old, spayed female Pug was evaluated for a corneal perforation of the right eye, which was surgically stabilized with a conjunctival pedicle graft. At the time of medial canthoplasty 7 weeks later, two areas of gray-white discoloration had developed medial and lateral to the graft. Biopsy samples were obtained via superficial keratectomy while under general anesthesia.

RESULTS

Definitive diagnosis of corneal SCC was made through histopathological examination of the surgical biopsies. Thoracic radiography and submandibular lymph node cytology revealed no evidence of metastatic neoplasia. Following healing of the corneal biopsy sites, topical 1% 5-FU ointment was applied four times daily for four consecutive days once a month, for six treatment cycles. Twenty-three months after diagnosis, the patient remains visual and comfortable with no evidence of SCC recurrence. Long-term therapy with once daily topical 1% cyclosporine solution was used to manage corneal pigmentation bilaterally.

CONCLUSIONS

The pulse-therapy 1% 5-FU protocol was a successful, convenient, and cost-effective adjunctive treatment with few adverse effects.

Electroretinogram evaluation of equine eyes with extensive 'bullet-hole' fundic lesions

OBJECTIVE

To evaluate the impact of extensive bullet-hole nontapetal fundic lesions in horses on retinal function as measured by full-field electroretinography (ERG).

MATERIALS AND METHODS

Full-field ERG was performed on two horses with numerous bullet-hole lesions in the nontapetal fundus of both eyes. The ERG was first recorded from the eye with the more extensive lesions in response to a low-intensity light stimulus (0.03 cd s/m(2) ) that was given at times (T) T = 5, 10, 15, 20 min of dark adaptation. Consecutively, combined rod-cone response was evaluated bilaterally in response to high-intensity light stimulus (3 cd s/m(2) ), followed by cone function evaluation by flicker stimulus (3 cd s/m(2) at 30 Hz). Off-line analysis of the ERG recordings was then performed.

RESULTS

Despite extensive bullet-hole lesions in the nontapetal fundus bilaterally in both horses, retinal function as measured by ERG did not show any observable deficits. The b-wave amplitude of the full-field ERG increased continuously from 5 to 20 min of dark adaptation peaking at 446 μv and 377 μv for horse number 1 and 2, respectively. The b-wave amplitudes of the combined rod-cone response were OS- 459 μv and OD- 392 μv for horse number 1 and OS- 491 μv and OD- 608 μv for horse number 2. The amplitude of the flicker ERG for horse number 1 was OS- 86 μv and OD- 110 μv and for horse number 2, OS- 80 μv and OD- 74 μv.

CONCLUSIONS

Extensive bullet-hole chorioretinal lesions do not appear to compromise outer retinal function in these horses.

Corneal sensitivity in healthy bovine calves

OBJECTIVE

To evaluate corneal sensitivity as measured by the corneal touch threshold in healthy bovine calves.

ANIMALS STUDIED

Twelve clinically normal male calves with predominantly Holstein genetics and a median age of 76.5 days (range, 67-92 days).

PROCEDURES

Corneal touch threshold (CTT) of the central cornea was measured in both eyes of each calf using a Cochet-Bonnet aesthesiometer.

RESULTS

The mean ± standard deviation corneal touch threshold of all eyes was 1.33 ± 1.1 g/mm(2) (range, 0.62-66.15 g/mm(2) ), corresponding to a filament length of 34.56 ± 8.02 mm (range, 14-47.5 mm). There was no significant difference between fellow eyes.

CONCLUSIONS

Cochet-Bonnet aesthesiometry was well tolerated in all 12 calves using a modified head restraint. Calves in this study may have a relatively sensitive central cornea compared to adult cattle and some other species; however, wide variation among individuals and eyes may be possible. Studies utilizing larger calf populations are necessary to establish reference ranges.

Effects of oral administration of anti-inflammatory medications on inhibition of paracentesis-induced blood-aqueous barrier breakdown in clinically normal cats

OBJECTIVE

To assess inhibitory effects of orally administered anti-inflammatory medications on paracentesis-induced intraocular inflammation in clinically normal cats.

ANIMALS

30 clinically normal domestic shorthair cats.

PROCEDURES

Cats were randomly assigned to a control group and 4 treatment groups. Cats in the treatment groups received an anti-inflammatory medication orally once daily at 7 AM (acetylsalicylic acid [40.5 mg/cat], meloxicam [0.1 mg/kg], prednisone [5 mg/cat], or prednisolone [5 mg/cat]) for 5 days beginning 2 days before paracentesis-induced breakdown of the blood-aqueous barrier (BAB) and continuing until 2 days after paracentesis. Paracentesis of the anterior chamber was performed in 1 randomly selected eye of each cat. Fluorophotometry was performed in both eyes of each cat immediately before (time 0) and 6, 24, and 48 hours after paracentesis.

RESULTS

At 24 and 48 hours after paracentesis, fluorescein concentration in the eye subjected to paracentesis in the cats receiving prednisolone was decreased, compared with that in the control cats. At 48 hours, a decrease in the fluorescein concentration was also apparent in the eye subjected to paracentesis in the cats receiving meloxicam, compared with that in the control cats. There was no evidence of treatment effects for acetylsalicylic acid or prednisone. There was no evidence of treatment effects in eyes not subjected to paracentesis.

CONCLUSIONS AND CLINICAL RELEVANCE

Orally administered prednisolone and meloxicam significantly decreased intraocular inflammation in clinically normal cats with paracentesis-induced BAB breakdown. Oral administration of prednisolone or meloxicam may be an effective treatment for cats with uveitis.

Investigation into the impact of audience response devices on short- and long-term content retention

Audience Response Systems (ARSs) may enhance short-term knowledge retention. Long-term knowledge retention is more difficult to demonstrate. According to previous studies, ARS questions requiring application of knowledge or peer interaction are more effective in maintaining student attention. The purpose of this study was to determine if peer discussion or individual-knowledge questions enhance short- and/or long-term knowledge retention. Third-year veterinary students responded to ARS questions posed in individual knowledge (n=3 questions) and peer discussion (n=3 questions) format from six different instructors. To test short-term memory, the same questions were delivered during the course examination (within 21 days). To test long-term retention, these questions were posed during a retention exercise (four months later). On the course examination, students had a higher (p<.01) probability (±SE) of correctly answering ARS individual-knowledge questions (93.8 ± 1.8%) compared to novel (previously unseen, non-ARS control) course examination questions (87.5 ± 3.1%), but the probability of correctly answering examination questions previously posed using ARS peer discussion format (89.5 ± 3.0%) did not differ from individual knowledge or novel examination questions. The positive impact of ARS-knowledge questions was not maintained through the retention exercise. Neither individual knowledge (70.5 ± 6.4%) nor peer-discussion questions (67.5 ± 6.9%) performed better on the retention exercise than the questions that appeared only on the course examination (68.6 ± 6.1%). Curricular strategies that emphasize content review may be more powerful than strategies that strengthen initial learning for long-term content retention.

Effects of ocular administration of ophthalmic 2% dorzolamide hydrochloride solution on aqueous humor flow rate and intraocular pressure in clinically normal cats

OBJECTIVE

To determine the effects of ocular administration of ophthalmic 2% dorzolamide hydrochloride solution on aqueous humor flow rate (AHFR) and intraocular pressure (IOP) in clinically normal cats.

ANIMALS

20 clinically normal domestic shorthair cats.

PROCEDURES

Following an acclimation period, IOP was measured in each eye of all cats 5 times daily for 3 days to determine baseline values. Fifteen cats received 1 drop of 2% dorzolamide solution and 5 cats received 1 drop of control solution in each eye every 8 hours for 5 days (treatment phase). The IOP of each eye was measured 5 times during each day of the treatment phase. Prior to and after the treatment phase, AHFR in both eyes of each cat was measured via fluorophotometry.

RESULTS

Prior to treatment, AHFR or IOP did not differ between the treatment and control groups. In dorzolamide-treated cats, mean AHFR after the treatment phase (3.47 ± 1.5 μL/min) was significantly lower than the value prior to treatment (5.90 ± 2.2 μL/min) and mean IOP during the treatment phase (11.1 ± 1.0 mm Hg) was significantly lower than the baseline mean IOP (14.9 ± 1.0 mm Hg). In the control group, IOP values did not differ before or during the treatment phase and AHFRs did not differ before and after the treatment phase.

CONCLUSIONS AND CLINICAL RELEVANCE

Ocular administration of 2% dorzolamide solution significantly decreased AHFR and IOP in clinically normal cats. Application of 2% dorzolamide solution may be an effective treatment in cats with glaucoma.

Repeated anterior chamber fluorophotometric evaluation of the eyes of ophthalmologically normal dogs

OBJECTIVE

To perform repeated anterior chamber fluorophotometry on both eyes of ophthalmologically normal dogs to measure fluorescein concentrations over a 5-day period and identify any change in the degree of anterior chamber fluorescence over time or difference between eyes.

ANIMALS

9 healthy adult dogs (18 eyes).

PROCEDURES

Each dog received an IV injection of 10% fluorescein solution, and anterior chamber fluorophotometry was performed 1 hour later on both eyes. This procedure was repeated at the same time each day for 5 consecutive days.

RESULTS

A significant increase in fluorescein concentration was evident in the anterior chamber on day 5 in the right eye and days 2, 3, 4, and 5 in the left eye. There was no significant difference in concentration between the left and the right eyes on any day.

CONCLUSIONS AND CLINICAL RELEVANCE

The increase in ocular fluorescein concentration in the study dogs was unlikely to be of clinical importance and is only pertinent for subsequent research studies. This is a limitation that should be considered when reporting fluorophotometry data as fluorescein concentration or as change in fluorescein concentration from baseline.