Objective—To determine whether epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor 2 (HER2) are expressed in periocular squamous cell carcinomas (SCCs) of horses.
Sample—Biopsy specimens of SCCs from 46 horses.
Procedures—Pathology records were searched retrospectively for biopsy specimens of periocular SCCs obtained from horses. Slides of the specimens were reviewed histologically to confirm the SCC diagnosis and stained for EGFR and HER2 by immunohistochemical methods. For both EGFR and HER2, the immunohistochemical staining intensity and percentage of stain-positive cells on the slides were determined.
Results—43 of 46 (93%) SCCs were immunoreactive for EGFR. The median score for EGFR staining intensity was 4 (range, 2 to 12), and the median number of mitotic figures was 8 mitotic figures/10 hpfs (range, 0 to 34 mitotic figures/10 hpfs). Mitotic index was not correlated with the percentage of EGFR stain–positive cells or staining intensity. Of the 43 EGFR-immunoreactive SCCs, 38 had stain present primarily in the cytoplasm and 5 had stain equally distributed between the cytoplasm and cell membranes. Thirty-five of 46 (76%) SCCs were immunoreactive for HER2. Mitotic index was not correlated with the percentage of HER2 stain–positive cells or staining intensity. Of the 35 HER2-immunoreactive SCCs, the stain was present primarily in the cytoplasm and 7 had stain equally distributed between the cytoplasm and cell membranes.
Conclusions and Clinical Relevance—Results indicated that most periocular SCCs of horses expressed EGFR and HER2, which suggested that equine periocular SCCs might respond to treatment with EGFR inhibitors.
Objective—To determine magnitude and duration of
the effect of oral administration of methazolamide at
2 dosages on intraocular pressure (IOP) in dogs in single-
dose and multiple-dose trials and to determine
aqueous humor flow rate (AHFR) by use of anterior
segment fluorophotometry before and during treatment.
Animals—25 healthy adult Beagles.
Procedure—Baseline IOPs and AHFRs were determined
on days 0 and 1, respectively. On day 2, the
single-dose trial was initiated with oral administration
of 25 or 50 mg of methazolamide at 7 AM to 2 groups
of 10 dogs each. Five dogs served as controls. In the
multiple-dose trial, the same dogs received 25 or 50
mg of methazolamide at 7 AM and at 3 and 11 PM on
days 3 through 9.
Results—Intraocular pressures varied diurnally with
highest IOPs in the morning. In the single-dose trial,
IOP decreased significantly at 3 to 6 hours after treatment
and then increased significantly at later time
points, compared with baseline values. In the multipledose
trial, dogs in both treatment groups had significantly
lower IOPs during the treatment period at 10 AM
and 1 PM but not at 6 and 9 PM, compared with baseline
values. In both treatment groups morning IOPs
had returned to baseline values by the first day after
treatment. Evening IOPs were significantly increased
by 2 to 3 days after treatment, compared with baseline
values. The AHFRs in both treatment groups were significantly
lower than pretreatment AHFRs.
Conclusions and Clinical Relevance—Oral administration
of methazolamide decreases IOPs and AHFRs
in clinically normal dogs, with effectiveness diminishing
in the evening. (Am J Vet Res 2003;64:183–187)
OBJECTIVE To evaluate the tear film osmolality and electrolyte composition in healthy horses.
ANIMALS 15 healthy adult horses.
PROCEDURES Each horse was manually restrained, and an ophthalmic examination, which included slit-lamp biomicroscopy, indirect ophthalmoscopy, and a Schirmer tear test, was performed. Tear samples were collected from both eyes with microcapillary tubes 3 times at 5-minute intervals. The tear samples for each horse were pooled, and the osmolality and electrolyte concentrations were measured. The mean (SD) was calculated for each variable to establish preliminary guidelines for tear film osmolality and electrolyte composition in healthy horses.
RESULTS The mean (SD) tear film osmolality was 283.51 (9.33) mmol/kg, and the mean (SD) sodium, potassium, magnesium, and calcium concentrations were 134.75 (10), 16.3 (5.77), 3.48 (1.97), and 1.06 (0.42) mmol/L, respectively. The sodium concentration in the tear film was similar to that in serum, whereas the potassium concentration in the tear film was approximately 4.75 times that of serum.
CONCLUSIONS AND CLINICAL RELEVANCE Results provided preliminary guidelines with which tear samples obtained from horses with keratopathies can be compared. Measurement of tear film osmolality in these horses was easy and noninvasive. The tear film concentration of divalent cations was greater than expected and was higher than the divalent cation concentrations in the tear films of rabbits and humans. These data may be clinically useful for the diagnosis and monitoring of hyperosmolar ocular surface disease in horses.
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.
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
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)
Objective—To evaluate effects of topical application
of a 2% solution of dorzolamide on intraocular pressure
(IOP) and aqueous humor flow rate in clinically
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
Objective—To determine effects of commonly used
ophthalmic antibiotics on cellular morphologic characteristics
and migration of canine corneal epithelium in
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
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.
OBJECTIVE To describe qualitative blinking patterns and determine quantitative kinematic variables of eyelid motion in ophthalmologically normal horses.
ANIMALS 10 adult mares.
PROCEDURES High-resolution videography was used to film blinking behavior. Videotapes were analyzed for mean blink rate, number of complete versus incomplete blinks, number of unilateral versus bilateral blinks, and subjective descriptions of blinking patterns. One complete blink for each horse was analyzed with image-analysis software to determine the area of corneal coverage as a function of time during the blink and to calculate eyelid velocity and acceleration during the blink.
RESULTS Mean ± SD blink rate was 18.9 ± 5.5 blinks/min. Blinks were categorized as minimal incomplete (29.7 ± 15.6%), moderate incomplete (33.5 ± 5.9%), complete (30.8 ± 13.1%), and complete squeeze (6.0 ± 2.8%); 22.6 ± 9.0% of the blinks were unilateral, and 77.3 ± 9.1% were bilateral. Mean area of exposed cornea at blink initiation was 5.89 ± 1.02 cm2. Mean blink duration was 0.478 seconds. Eyelid closure was approximately twice as rapid as eyelid opening (0.162 and 0.316 seconds, respectively). Deduced maximum velocity of eyelid closure and opening was −16.5 and 7.40 cm/s, respectively. Deduced maximum acceleration of eyelid closure and opening was −406.0 and −49.7 cm/s2, respectively.
CONCLUSIONS AND CLINICAL RELEVANCE Kinematic variables of ophthalmologically normal horses were similar to values reported for humans. Horses had a greater percentage of complete squeeze blinks, which could increase tear film stability. Blinking kinematics can be assessed as potential causes of idiopathic keratopathies in horses.