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- Author or Editor: Steven R. Hollingsworth x
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Abstract
Objective—To measure the dimensions of the eyes of living snakes by use of high-frequency ultrasound imaging and correlate those measurements with age, length, and weight.
Animals—14 clinically normal snakes.
Procedures—Species, age, length, weight, and horizontal spectacle diameter were recorded, and each snake underwent physical and ophthalmic examinations; ultrasonographic examination of both eyes was performed by use of a commercially available ultrasound unit and a 50-MHz transducer. Ultrasonographic measurements included spectacle thickness, subspectacular space depth, corneal thickness, anterior chamber depth, lens thickness, vitreous cavity depth, and globe length. All measurements were made along the visual axis.
Results—2 corn snakes, 5 California king snakes, 1 gopher snake, and 6 ball pythons were examined. There were no significant differences within or between the species with regard to mean spectacle thickness, corneal thickness, or subspectacular space depth. However, mean horizontal spectacle diameter, anterior chamber depth, and axial globe length differed among the 4 species; for each measurement, ball pythons had significantly larger values than California king snakes.
Conclusions and Clinical Relevance—Spectacle thickness, subspectacular space depth, and corneal thickness were similar among the species of snake examined and did not vary significantly with age, length, or weight. Measurements of these dimensions can potentially serve as baseline values to evaluate snakes of these species with a retained spectacle, subspectacular abscess, or subspectacular fluid accumulation. Anterior chamber depth and axial length appeared variable among species, but axial length did not vary with age, length, or weight in the species studied.
Abstract
Objective—To compare aesthesiometer-determined corneal sensitivity between diabetic and nondiabetic dogs and to investigate the correlation between corneal sensitivity and duration of diabetes or status of glycemic control, as estimated by use of glycated blood protein concentrations.
Animals—23 diabetic and 29 nondiabetic normoglycemic dogs.
Procedure—A Cochet-Bonnet aesthesiometer was used to measure corneal touch threshold (CTT) in 5 corneal regions of each dog. At the time of ocular examination, duration of diabetes mellitus was estimated from the history, and blood was drawn for assessment of blood glycosylated hemoglobin and serum fructosamine concentrations.
Results—Median CTT for central, nasal, dorsal, temporal, and ventral corneal regions in nondiabetic dogs (1.6, 2.3, 2.8, 2.8, and 5.1 g/mm2, respectively) was significantly lower than in diabetic dogs (2.8, 4.0, 5.1, 5.1, and 6.6 g/mm2, respectively). Median regional CTT in diabetic dogs was not significantly correlated with estimated duration of diabetes mellitus or blood glycated protein concentrations. No significant difference was found in regional CTT between eyes of normoglycemic dogs with unilateral cataracts.
Conclusion and Clinical Relevance—Diabetic dogs have significantly reduced corneal sensitivity in all regions, compared with nondiabetic normoglycemic dogs. Regional variation in corneal sensitivity is similar in diabetic and normoglycemic dogs. Neither glycemic control nor duration of diabetes, as estimated, is significantly correlated with corneal hyposensitivity. Corneal nerve dysfunction may be associated with recurrent or nonhealing ulcers in diabetic dogs for which no other underlying cause can be found. (Am J Vet Res 2003;64:7–11)
Abstract
Objective—To measure the effect of induced myopia on field trial performance in dogs.
Animals—7 Labrador Retrievers and 1 Chesapeake Bay Retriever trained in field trial competition.
Procedures—Dogs were commanded to retrieve targets at 137.2 m (150 yards). Each dog participated in 3 trials while their eyes were fitted with 0- (plano), +1.50-, or +3.00-diopter (D) contact lenses, applied in random order. Retrieval times were measured objectively, and dog performances were evaluated subjectively by masked judges.
Results—Retrieval times were significantly faster with plano lenses than with +1.50- or +3.00-D lenses, but there were no significant differences in times between +1.50- and +3.00-D lenses. Masked judges assigned the best performance scores to dogs with plano lenses and the lowest scores to dogs fitted with +3.00-D lenses.
Conclusions and Clinical Relevance—Even mild myopic defocusing had a significant negative impact on both the subjective and objective assessments of dogs' performances. Dogs with demanding visual tasks or signs of visual deterioration should be evaluated retinoscopically to determine the refractive state because they may have ametropia.
Abstract
Objective—To assess the effects of ketamine hydrochloride, propofol, or compounded thiopental sodium administration on intraocular pressure (IOP) and qualities of induction of and recovery from anesthesia in horses.
Animals—6 healthy adult horses.
Procedures—Horses were sedated with xylazine hydrochloride (0.5 mg/kg), and anesthesia was induced with guaifenesin followed by ketamine (2 mg/kg), propofol (3 mg/kg), or thiopental (4 mg/kg) in a crossover study with ≥ 1 week between treatments. For each horse, IOP in the right eye was measured with a handheld applanation tonometer before and after xylazine administration, at the time of recumbency, and every 3 minutes after induction of anesthesia until spontaneous movement was observed. Cardiorespiratory responses and venous blood measurements were recorded during anesthesia. Induction of and recovery from anesthesia were subjectively evaluated by investigators who were unaware of the anesthetic treatment of each horse. Data were analyzed via a repeated-measures ANOVA with Holm-Ŝidák post hoc comparisons.
Results—Compared with findings after xylazine administration (mean ± SD, 17 ± 3 mm Hg), thiopental decreased IOP by 4 ± 23%, whereas propofol and ketamine increased IOP by 8 ± 11% and 37 ± 16%, respectively. Compared with the effects of ketamine, propofol and thiopental resulted in significantly lower IOP at the time of recumbency and higher heart rates at 3 minutes after induction of anesthesia. No other significant differences among treatments were found.
Conclusions and Clinical Relevance—These findings support the use of thiopental or propofol in preference to ketamine for horses in which increases in IOP should be minimized.
Abstract
Objective—To characterize heritability and mode of inheritance of cataracts and primary lens luxation in Jack Russell Terriers.
Animals—872 Jack Russell Terriers from which buccal epithelial cells were collected and phenotypes for cataracts and lens luxation were determined and an additional 1,898 Jack Russell Terriers without phenotypic information used to complete pedigree relationships and that were included in the analyses.
Procedures—Narrow-sense heritabilities and genetic correlation for cataracts and lens luxation were modeled by use of threshold analysis, whereas complex segregation analysis was used to characterize mode of inheritance. For the analyses, dogs < 6 years old, unless confirmed as having cataracts or lens luxation, were classified as an unknown phenotype. The possible involvement of an HSF4 mutation in cataracts was determined by DNA sequencing.
Results—Cataracts and primary lens luxation were highly heritable and genetically correlated, and neither was controlled by a single gene. Cataracts were not associated with an HSF4 mutation.
Conclusions and Clinical Relevance—Analysis of the data indicated that concerted selection against both cataracts and primary lens luxation when choosing breeding animals can be used to improve ocular health in Jack Russell Terriers.
Abstract
Objective—To describe clinical and diagnostic imaging features of zygomatic sialadenitis in dogs.
Design—Retrospective case series.
Animals—11 dogs with zygomatic sialadenitis and 20 control dogs without evidence of retrobulbar disease.
Procedures—Medical records were searched for dogs with zygomatic sialadenitis that underwent some combination of magnetic resonance imaging (MRI), computed tomography (CT), and ultrasonography. Signalment, clinical signs, results of clinicopathologic tests, cytologic and histologic diagnosis, treatment, qualitative disease features, and disease course were recorded. Images obtained via MRI or CT were analyzed for pre- and postcontrast signal intensity or density, respectively; zygomatic salivary gland area was determined. Results were compared with those of control dogs that underwent the same imaging procedures (n = 10/method). Ultrasonographic images of affected dogs were assessed qualitatively.
Results—Most (9/11) affected dogs were medium- or large-breed males (mean age, 8 years) with unilateral disease. Affected dogs had clinical signs of retrobulbar disease and cytologic or histologic evidence of zygomatic sialadenitis. Sialoceles were detected in 7 affected glands. Compared with values for control dogs, MRI findings in affected dogs (n = 7) included gland enlargement, T1-weighted hypointensity, T2-weighted hyperintensity, and increased contrast enhancement; CT features in affected dogs (2) included gland enlargement and hypodensity on unenhanced images. Retrobulbar masses were identified via ultrasonography in 9 of 10 orbits examined, and zygomatic salivary gland origin was detected in 4.
Conclusions and Clinical Relevance—Visualization of anatomic structures for diagnosis of zygomatic sialadenitis and evaluation of adjacent structures was excellent via MRI and CT Ultrasonography was less definitive but useful for sample collection.
Abstract
OBJECTIVE
To compare intraocular pressures (IOPs) estimated by rebound and applanation tonometry for dogs with lens instability.
ANIMALS
66 dogs.
PROCEDURES
Medical records of dogs examined between September 2012 and July 2018 were reviewed for diagnoses of anterior (ALL) or posterior (PLL) lens luxation or lens subluxation.
RESULTS
Estimates of IOP obtained with rebound and applanation tonometry significantly differed from each other for all types of lens instability considered collectively (mean ± SE difference between tonometric readings, 8.1 ± 1.3 mm Hg) and specific types of lens instability considered individually (mean ± SE difference between tonometric readings: ALL, 12.8 ± 2.5 mm Hg; PLL, 5.9 ± 1.7 mm Hg; subluxation, 2.8 ± 0.8 mm Hg). Median (range) differences between rebound and applanation tonometer readings for dogs with ALL was 5 mm Hg (–9 to 76 mm Hg), with PLL was 3 mm Hg (–1 to 19 mm Hg), and with lens subluxation was 3 mm Hg (–9 to 18 mm Hg). In eyes with ALL, rebound tonometer readings exceeded applanation tonometer readings on 44 of 60 (73%) occasions.
CONCLUSIONS AND CLINICAL RELEVANCE
Rebound tonometry yielded higher estimates of IOP than did applanation tonometry in eyes with ALL and with all types of lens luxation considered collectively. Estimates of IOP in eyes with lens instability should ideally be obtained with both rebound and applanation tonometers. Veterinarians with only one type of tonometer should interpret results for dogs with lens instability concurrent with physical examination findings.
Abstract
OBJECTIVE To describe diagnosis, treatment, and outcome of and risk factors for ophthalmic disease in leopard geckos (Eublepharis macularius) evaluated at a veterinary teaching hospital.
DESIGN Retrospective case series.
ANIMALS 112 of 144 (78%) leopard geckos that were evaluated at a veterinary teaching hospital in January 1985 through October 2013 and for which sufficient medical record information was available.
PROCEDURES Information from medical records was used to identify leopard geckos with ophthalmic disease, characterize cases, and determine risk factors for the presence of ophthalmic disease.
RESULTS Of the 112 leopard geckos, 52 (46%) had ophthalmic disease (mainly corneal or conjunctival disease). Female geckos were less likely to have ophthalmic disease, and there was a positive association between increasing age and ophthalmic disease. Use of a paper towel substrate, absence of any heat source, and lack of vitamin A supplementation were positively associated with a diagnosis of ophthalmic disease. Head dysecdysis was the only concurrent disorder significantly associated with ophthalmic disease. At necropsy, 5 affected leopard geckos had squamous metaplasia of the conjunctivae.
CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that ophthalmic disease is a common finding in leopard geckos. The cause of ocular surface disease in leopard geckos may be multifactorial, and hypovitaminosis A may be an important risk factor. Although animals receiving supplemental vitamin A were less likely to have ophthalmic disease, further understanding is required regarding the metabolism of and nutritional requirements for vitamin A in leopard geckos.
Abstract
Objective—To determine the distribution and clinical outcome of ocular lesions in snakes.
Design—Retrospective case series.
Animals—67 snakes with ocular lesions.
Procedures—Signalment, lesion duration, diagnosis, treatment, and clinical outcome were recorded for all snakes with ocular lesions that were examined at a veterinary teaching hospital from 1985 to 2010.
Results—71 ocular lesions were detected in 67 of 508 (13%) snakes examined. Affected snakes were of the families Boidae, Pythonidae, Colubridae, and Viperidae. The distribution of ocular lesions did not vary by taxonomic family, age, or sex; however, snakes from the genus Epicrates with ocular lesions were overrepresented in the population. The most commonly diagnosed ocular lesions were retained spectacle (n = 41), pseudobuphthalmos or subspectacular abscess (13), trauma (8), and cataracts (4). Pseudobuphthalmos or subspectacular abscess developed more frequently in Colubridae than in non-Colubridae snakes. Of the 16 snakes with retained spectacles for which data were available, the lesion recurred once in 4 snakes and multiple times in 5 snakes.
Conclusions and Clinical Relevance—Results indicated that retained spectacle was the most common ocular lesion diagnosed in snakes. Compared with other snakes with ocular lesions, snakes of the genus Epicrates had a higher than expected frequency of ocular lesions in general and snakes of the family Colubridae had a higher than expected frequency of pseudobuphthalmos or subspectacular abscess.
Summary
Baseline tear production values were established for both eyes of 19 dogs, using the Schirmer tear test. Atropine sulfate, 1% solution, was administered topically in the left eye of each dog once daily for 14 days. Tear production was then determined for both eyes at 15, 30, 60, 120, 180, 240, and 300 minutes, and 3, 6, 9, 12, and 15 days. A final Schirmer tear test reading was obtained for each eye 5 weeks after the last atropine treatment to check for the possibility of prolonged effect. Both eyes had statistically significant (P < 0.05) decrease in tear production that was most marked at 120 minutes after atropine instillation, then returned to baseline values by 300 minutes after instillation. Although atropine was placed in the left eye only, statistically significant difference was not apparent in Schirmer tear test values between the left and right eyes. Tear production continued to decrease in both eyes over time, becoming statistically significant (P < 0.05) on day 9. However, on days 12 and 15, tear production in the untreated eye plateaued, but that in the treated eye continued to decrease. Five weeks after the last treatment with atropine, both eyes still had a statistically significant (P < 0.05) decrease in tear production, although Schirmer tear test values had increased from day-15 values and appeared to be returning to baseline. Association was not evident between age or body weight and magnitude of response to topically applied atropine.