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Ström L, Michanek M, Ekesten B. Age‐associated changes in the equine flash visual evoked potential. Vet Ophthalmol 2018; 22:388-397. [DOI: 10.1111/vop.12601] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Lena Ström
- Department of Clinical Sciences Swedish University of Agricultural Sciences Uppsala Sweden
| | - Måns Michanek
- Referral Animal Hospital Strömsholm Strömsholm Sweden
| | - Björn Ekesten
- Department of Clinical Sciences Swedish University of Agricultural Sciences Uppsala Sweden
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Abstract
BACKGROUND Electrical potentials generated in the central nervous system in response to brief visual stimuli, flash visual evoked potentials (FVEPs), can be recorded non-invasively over the occipital cortex. FVEPs are used clinically in human medicine and also experimentally in a number of animal species, but the method has not yet been evaluated in the horse. The method would potentially allow the ophthalmologist and equine clinician to evaluate visual impairment caused by disorders affecting post-retinal visual pathways. The aim was to establish a method for recording of FVEPs in horses in a clinical setting and to evaluate the waveform morphology in the normal horse. METHODS Ten horses were sedated with a continuous detomidine infusion. Responses were recorded from electrodes placed on the scalp. Several positions were evaluated to determine suitable electrode placement. Flash electroretinograms (FERGs) were recorded simultaneously. To evaluate potential contamination of the FVEP from retinal potentials, a retrobulbar nerve block was performed in two horses and transection of the optic nerve was performed in one horse as a terminal procedure. RESULTS A series of positive (P) and negative (N) peaks in response to light stimuli was recorded in all horses. Reproducible wavelets with mean times-to-peaks of 26 (N1), 55 (P2), 141 (N2) and 216 ms (P4) were seen in all horses in all recordings. Reproducible results were obtained when the active electrode was placed in the midline rostral to the nuchal crest. Recording at lateral positions gave more variable results, possibly due to ear muscle artifacts. Averaging ≥100 responses reduced the impact of noise and artifacts. FVEPs were reproducible in the same horse during the same recording session and between sessions, but were more variable between horses. Retrobulbar nerve block caused a transient loss of the VEP whereas transection of the optic nerve caused an irreversible loss. CONCLUSIONS We describe the waveform of the equine FVEP and our results show that it is possible to record FVEPs in sedated horses in a clinical setting. The potentials recorded were shown to be of post-retinal origin. Further studies are needed to provide normative data and assess potential clinical use.
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Affiliation(s)
- L Ström
- Department of Clinical Sciences, Swedish University of Agricultural Sciences, PO Box 7054, SE-750 07, Uppsala, Sweden.
| | - B Ekesten
- Department of Clinical Sciences, Swedish University of Agricultural Sciences, PO Box 7054, SE-750 07, Uppsala, Sweden
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Leis ML, Dodd MMU, Starrak G, Vermette CJ, Gomis S, Bauer BS, Sandmeyer LS, Schwean-Lardner K, Classen HL, Grahn BH. Effect of prolonged photoperiod on ocular tissues of domestic turkeys. Vet Ophthalmol 2016; 20:232-241. [PMID: 27302599 DOI: 10.1111/vop.12395] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE The objective of this study is to investigate the structural and functional ocular changes that develop in turkeys exposed to a photoperiod of 23 h of light (23L) compared with a photoperiod of 14 h of light (14L). PROCEDURES Ten-day-old Nicholas heavy strain poults were exposed to either a 14L or 23L photoperiod. Between 16 and 18 weeks of age, equal numbers of turkeys per treatment group underwent ophthalmic examination (biomicroscopy, indirect ophthalmoscopy) (n = 14), refractometry (n = 20), keratometry (n = 20), tonometry (n = 20), and full-field electroretinography (ERG) (n = 14). Postmortem analyses included orbital magnetic resonance imaging (MRI) (n = 10) and light microscopy (n = 24) at 18 weeks of age. RESULTS Autorefraction revealed a median of -0.13 for sphere in both groups (P = 0.69), which is approximately emmetropia. The radius of curvature of the cornea was significantly higher (P = 0.0001) and the refractive power of the cornea was significantly lower (P = 0.0001) in the 23L group. The astigmatic power was significantly greater in the 23L group (P = 0.0001). Mean intraocular pressure did not differ between groups (P = 0.085). Turkeys from the 23L group had significantly larger globes in nasotemporal (P = 0.0007), dorsoventral (P = 0.015), and anterioposterior (P = 0.021) directions, and anterior chambers were more shallow (P = 0.0002). ERGs revealed the 23L group to have lower a- and b-wave amplitudes and significantly lower cone flicker amplitudes (P = 0.0008). Light microscopic examination revealed 23L turkeys to have significantly decreased numbers of nuclei in the outer nuclear layer (P = 0.0001) and inner nuclear layer (P = 0.0186), and decreased choroidal thickness (P = 0.0008). The prevalence of cataract in the 23L group was significantly higher (P = 0.001). CONCLUSIONS Exposing turkeys to a prolonged photoperiod induces significant ocular disease.
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Affiliation(s)
- Marina L Leis
- Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK, Canada
| | | | - Gregory Starrak
- Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK, Canada
| | - Catherine J Vermette
- College of Agriculture and Bioresources, University of Saskatchewan, Saskatoon, SK, Canada
| | - Susantha Gomis
- Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK, Canada
| | - Bianca S Bauer
- Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK, Canada
| | - Lynne S Sandmeyer
- Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK, Canada
| | - Karen Schwean-Lardner
- College of Agriculture and Bioresources, University of Saskatchewan, Saskatoon, SK, Canada
| | - Henry L Classen
- College of Agriculture and Bioresources, University of Saskatchewan, Saskatoon, SK, Canada
| | - Bruce H Grahn
- Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK, Canada
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Augsburger AS, Haag V, Leuillet S, Legrand JJ, Forster R. Recording of the full-field electroretinogram in minipigs. Vet Ophthalmol 2012; 15 Suppl 2:84-93. [PMID: 22830305 DOI: 10.1111/j.1463-5224.2012.01052.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
PURPOSE To test a simple electroretinographic protocol on a representative sample of minipigs. ANIMAL STUDIED Minipig. PROCEDURES Electroretinogram recordings were conducted on 162 healthy minipigs (81 males and 81 females) aged 4-6 months. After a 1.5-h light-adaptation period, the animals were anesthetized with general anesthesia. First, binocular full-field photopic electroretinogram recordings were conducted under photopic conditions. Subsequently, scotopic electroretinogram recordings were conducted during dark-adaptation periods every 4 min for a 20-min period. At the end of this period, the maximal combined rod-cone response was recorded by measuring the retinal response to a single high-intensity flash. We used sclerocorneal clip electrodes as active electrodes and needle electrodes as reference and ground electrodes. RESULTS The a-wave and b-wave peak times and amplitudes have been measured and statistically analyzed. For each of the statistical comparisons, normality and homogeneity of variances were evaluated. No significant gender differences were observed, with the exception of a higher b-wave amplitude for the photopic ERG recordings observed in females when compared to males (48.14 ± 12.909 μV vs. 42.88 ± 10.666 μV; P = 0.005). The process of dark adaptation was evaluated, and the maximal combined rod-cone response was measured (a- and b-waves amplitude and peak time). CONCLUSIONS We conducted photopic and scotopic electroretinogram recordings from a protocol based on light adaptation followed by dark adaptation using sclerocorneal clip electrodes, which allows quick assembly and examination.
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Harrington JT, McMullen RJ, Clode AB, Gilger BC. Phacoemulsification and +14 diopter intraocular lens placement in a Saddlebred foal. Vet Ophthalmol 2012; 16:140-8. [DOI: 10.1111/j.1463-5224.2012.01032.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Church ML, Norman JC. Electroretinogram responses of the normal thoroughbred horse sedated with detomidine hydrochloride. Vet Ophthalmol 2012; 15 Suppl 2:77-83. [PMID: 22498137 DOI: 10.1111/j.1463-5224.2012.01022.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
PURPOSE The main objective was to record electroretinogram (ERG) parameters of normal thoroughbred mares using the HMsERG, a mini-Ganzfeld electroretinographic unit, and a contact lens electrode. The second objective was to determine whether IV detomidine hydrochloride at 0.015 mg/kg is consistently an effective choice for sedation of horses undergoing this ERG protocol. METHODS The study population consisted of 30 normal thoroughbred mares. ERG data were harvested using a protocol that included three different light intensities (10, 3000, and 10,000 mcd s/m(2)) and a 30-Hz flicker at 3000 mcd s/m(2). RESULTS Mean, median, standard deviation, and estimated normal ranges using the 5-95% of the data for a- and b-wave implicit times (IT), amplitudes (AMP), and b/a ratios were reported. Scotopic results at low intensity (10 mcd s/m(2)) had estimated ranges for b-wave IT of 41.8-72.9 ms and AMP of 19.8-173.3 μV. Middle intensity (3000 mcd s/m(2)) a-wave IT was 13.2-14.7 ms with a-wave AMP of 68.4-144 μV; the b-wave IT was 28.7-41.5 ms with b-wave AMP of 105.7-271.5 μV; and the b/a ratio was 0.95-2.71. The high-intensity (10,000 mcd s/m(2)) average recordings showed an a-wave IT of 13-14.9 ms, a-wave AMP of 85.7-186.8 μV; b-wave IT of 26.6-45.4 ms, b-wave AMP of 104.7-250.6 μV; and a b/a wave ratio of 0.7-2.0. The 30-Hz cone flicker showed an IT of 22.8-28.9 ms and AMP of 44.1-117.1 μV. CONCLUSIONS Results of normal thoroughbred ERG responses are reported. The protocol proved to be simple and safe and provided consistent results.
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Affiliation(s)
- Melanie L Church
- Eye Care for Animals, 13034 W Rancho Santa Fe Blvd, Suite 102, Avondale, AZ 85392, USA.
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Finno CJ, Higgins RJ, Aleman M, Ofri R, Hollingsworth SR, Bannasch DL, Reilly CM, Madigan JE. Equine degenerative myeloencephalopathy in Lusitano horses. J Vet Intern Med 2012; 25:1439-46. [PMID: 22092640 DOI: 10.1111/j.1939-1676.2011.00817.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND Equine degenerative myeloencephalopathy (EDM) is a neurodegenerative disorder that has been previously associated with low vitamin E concentrations. OBJECTIVE To describe the clinical, electrophysiologic, and pathologic features of EDM in a group of related Lusitano horses. ANIMALS Fifteen Lusitano horses. PROCEDURES Neurologic examinations were conducted, and serum vitamin E concentrations were measured. Three neurologically abnormal horses were further evaluated by ophthalmologic examination, electroretinography, electroencephalography, muscle and nerve biopsies, and post-mortem examination. RESULTS Six horses appeared neurologically normal, 6 were neurologically abnormal, and 3 had equivocal gait abnormalities. Abnormal horses demonstrated ataxia and paresis. An inconsistent menace response was noted in 4 neurologically abnormal horses and in 1 horse with equivocal findings. All horses had low serum vitamin E concentrations (<1.5 ppm). Ophthalmologic examinations, electroretinograms, electroencephalograms, and muscle and peripheral nerve biopsies were unremarkable in 3 neurologically abnormal horses. At necropsy, major neuropathological findings in these horses were bilaterally symmetric, severe, neuro axonal degeneration in the gracilis, cuneatus medialis, cuneatus lateralis, and thoracicus nuclei and bilaterally symmetric axonal loss and demyelination mainly in the dorsolateral and ventromedial tracts of the spinal cord. A diagnosis of EDM was made based on these findings. Pedigree analysis identified 2 sires among the affected horses. CONCLUSIONS AND CLINICAL RELEVANCE Equine degenerative myeloencephalopathy is a neurodegenerative disorder that causes ataxia and, in severe cases, paresis, in young Lusitano horses. The disease appears to have a genetic basis, and although vitamin E deficiency is a common finding, low serum vitamin E concentrations also may occur in apparently unaffected related individuals.
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Affiliation(s)
- C J Finno
- William R. Pritchard Veterinary Medical Teaching Hospital, School of Veterinary Medicine, University of California Davis, CA 95616, USA.
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Finno CJ, Aleman M, Ofri R, Hollingsworth SR, Madigan JE, Winfield L, Bannasch DL. Electrophysiological studies in American Quarter horses with neuroaxonal dystrophy. Vet Ophthalmol 2012; 15 Suppl 2:3-7. [DOI: 10.1111/j.1463-5224.2012.00997.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Ben-Shlomo G, Plummer C, Barrie K, Brooks D. Characterization of the normal dark adaptation curve of the horse. Vet Ophthalmol 2011; 15:42-5. [DOI: 10.1111/j.1463-5224.2011.00923.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Townsend WM, Jacobi S, Bartoe JT. Phacoemulsification and implantation of foldable +14 diopter intraocular lenses in five mature horses. Equine Vet J 2011; 44:238-43. [DOI: 10.1111/j.2042-3306.2011.00392.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- W M Townsend
- Department of Small Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, MI, USA.
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Abstract
The purpose of this review is to discuss the evolution of equine cataract surgery over the past 50 years to its current stage. Equine cataract surgery is performed similarly compared with the techniques used in human ophthalmology and in other veterinary species. However, enough differences exist to make surgical lens removal and intraocular lens implantation in the horse an intrinsically unique endeavour. Due to the size of the adult equine globe, the introduction of species-specific instrumentation has provided the cornerstone to many of the changes made regarding surgical technique over the last 15-20 years. The continuing development of an equine specific, foldable intraocular lens implant (IOL) has provided much needed data supporting the use of such lenses in the horse to improve upon the post operative visual outcome. Finally, the methods utilised to assess visual capacity and the effects of intraocular lens implantation on the globe (e.g. ocular ultrasonography, electroretinography and streak retinoscopy) are gradually becoming more important in preoperative patient assessment and IOL development in the horse. It is the hope of the authors that a broader group of equine veterinarians will become aware of the many changes that have taken place in equine cataract surgery over the last half-century. Although aspiration was implemented nearly 40 years ago in foals for the treatment of congenital cataracts, phacofragmentation (phacoemulsification) techniques have only recently become routine in mature horses undergoing lens extraction.
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Affiliation(s)
- R J McMullen
- Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, 4700 Hillsborough Street, Raleigh, North Carolina 27613, USA
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Labelle AL, Hamor RE, Narfström K, Breaux CB. Electroretinography in the western gray kangaroo (Macropus fuliginosus). Vet Ophthalmol 2010; 13 Suppl:41-6. [DOI: 10.1111/j.1463-5224.2010.00810.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Douglas LC, Yi NY, Davis JL, Salmon JH, Gilger BC. Ocular toxicity and distribution of subconjunctival and intravitreal rapamycin in horses. J Vet Pharmacol Ther 2009; 31:511-6. [PMID: 19000272 DOI: 10.1111/j.1365-2885.2008.00986.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In vitro photosensitivity of rapamycin (RAPA) and ocular toxicity and distribution of intravitreal and subconjunctival RAPA was evaluated in normal horses. RAPA (2.5 mg, 5 mg, and 10 mg) was placed in 10 mL of PBS and maintained in a water bath at 37 degrees C, kept in the dark or subjected to room light, and sampled for up to 3 months for RAPA levels. Six normal adult horses received either 5 mg (n = 2) or 10 mg (n = 2) of RAPA intravitreally or 10 mg (n = 2) subconjunctivally. Ophthalmic exams and electroretinography (ERG) were performed prior to injection and on days 1, 7, 14, and 21 post-injection. Eyes were enucleated and samples were collected for RAPA concentrations and histopathology. No difference in light vs. dark RAPA concentrations was observed, suggesting a lack of RAPA phototoxicity. No evidence of ocular toxicity was noted on ophthalmic examination or histopathology. RAPA was not detected intraocularly 7 days post-injection in eyes receiving subconjunctival RAPA, but was detected in the vitreous at 21 days post-injection. Drug could be detected in both the aqueous and vitreous humor after intravitreal injection. Further study is needed to determine the efficacy of intravitreal RAPA.
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Affiliation(s)
- L C Douglas
- Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC 27606, USA
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Differential gene expression of TRPM1, the potential cause of congenital stationary night blindness and coat spotting patterns (LP) in the Appaloosa horse (Equus caballus). Genetics 2008; 179:1861-70. [PMID: 18660533 DOI: 10.1534/genetics.108.088807] [Citation(s) in RCA: 131] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The appaloosa coat spotting pattern in horses is caused by a single incomplete dominant gene (LP). Homozygosity for LP (LP/LP) is directly associated with congenital stationary night blindness (CSNB) in Appaloosa horses. LP maps to a 6-cM region on ECA1. We investigated the relative expression of two functional candidate genes located in this LP candidate region (TRPM1 and OCA2), as well as three other linked loci (TJP1, MTMR10, and OTUD7A) by quantitative real-time RT-PCR. No large differences were found for expression levels of TJP1, MTMR10, OTUD7A, and OCA2. However, TRPM1 (Transient Receptor Potential Cation Channel, Subfamily M, Member 1) expression in the retina of homozygous appaloosa horses was 0.05% the level found in non-appaloosa horses (R = 0.0005). This constitutes a >1800-fold change (FC) decrease in TRPM1 gene expression in the retina (FC = -1870.637, P = 0.001) of CSNB-affected (LP/LP) horses. TRPM1 was also downregulated in LP/LP pigmented skin (R = 0.005, FC = -193.963, P = 0.001) and in LP/LP unpigmented skin (R = 0.003, FC = -288.686, P = 0.001) and was downregulated to a lesser extent in LP/lp unpigmented skin (R = 0.027, FC = -36.583, P = 0.001). TRP proteins are thought to have a role in controlling intracellular Ca(2+) concentration. Decreased expression of TRPM1 in the eye and the skin may alter bipolar cell signaling as well as melanocyte function, thus causing both CSNB and LP in horses.
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Sandmeyer LS, Breaux CB, Archer S, Grahn BH. Clinical and electroretinographic characteristics of congenital stationary night blindness in the Appaloosa and the association with the leopard complex. Vet Ophthalmol 2007; 10:368-75. [PMID: 17970998 DOI: 10.1111/j.1463-5224.2007.00572.x] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
OBJECTIVE To determine the prevalence of congenital stationary night blindness (CSNB) in Appaloosa horses in western Canada, investigate the association with the leopard complex of white spotting patterns, and further characterize the clinical and electroretinographic aspects of CSNB in the Appaloosa. ANIMALS STUDIED Three groups of 10 Appaloosas were studied based on coat patterns suggestive of LpLp, Lplp, and lplp genotype. PROCEDURES Neurophthalmic examination, slit-lamp biomicroscopy, indirect ophthalmoscopy, measurement of corneal diameter, streak retinoscopy, scotopic and photopic full-field and flicker ERGs and oscillatory potentials (OPs) were completed bilaterally. RESULTS All horses in the LpLp group were affected by CSNB, while none in the Lplp or lplp groups was affected. The LpLp and Lplp groups had significantly smaller vertical and horizontal corneal diameters than the lplp group had. Median refractive error was zero for all groups. Scotopic ERGs in the LpLp (CSNB-affected) group were consistent with previous descriptions. The CSNB-affected horses had significantly longer photopic a-wave implicit times, greater a-wave amplitudes, and lower b-wave amplitudes than the Lplp and lplp (normal) groups did. No differences were present in photopic flicker amplitude or implicit times. Scotopic flickers in the CSNB-affected horses were markedly reduced in amplitude and abnormal in appearance. No differences were noted in OP implicit times; however, amplitudes of some OPs were reduced in CSNB-affected horses. There were no differences in scotopic and photopic or flicker ERGs or OPs between the normal groups. CONCLUSIONS CSNB was present in one-third of horses studied and there was a significant association between CSNB and the inheritance of two Lp alleles. ERG abnormalities support the hypothesis that CSNB is caused by a defect in neural transmission through the rod pathway involving the inner nuclear layer.
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Affiliation(s)
- Lynne S Sandmeyer
- Department of Small Animal Clinical Sciences, Western College of Veterinary Medicine University of Saskatchewan, 52 Campus Drive, Saskatoon, Saskatchewan, Canada S7N 584.
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Yu HA, Jeong MB, Park SA, Kim WT, Kim SE, Chae JM, Yi NY, Seo KM. The determination of dark adaptation time using electroretinography in conscious miniature Schnauzer dogs. J Vet Sci 2007; 8:409-14. [PMID: 17993756 PMCID: PMC2868158 DOI: 10.4142/jvs.2007.8.4.409] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The optimal dark adaptation time of electroretinograms (ERG's) performed on conscious dogs were determined using a commercially available ERG unit with a contact lens electrode and a built-in light source (LED-electrode). The ERG recordings were performed on nine healthy Miniature Schnauzer dogs. The bilateral ERG's at seven different dark adaptation times at an intensity of 2.5 cd·s/m2 was performed. Signal averaging (4 flashes of light stimuli) was adopted to reduce electrophysiologic noise. As the dark adaptation time increased, a significant increase in the mean a-wave amplitudes was observed in comparison to base-line levels up to 10 min (p < 0.05). Thereafter, no significant differences in amplitude occured over the dark adaptation time. Moreover, at this time the mean amplitude was 60.30 ± 18.47 µV. However, no significant changes were observed for the implicit times of the a-wave. The implicit times and amplitude of the b-wave increased significantly up to 20 min of dark adaptation (p < 0.05). Beyond this time, the mean b-wave amplitudes was 132.92 ± 17.79 µV. The results of the present study demonstrate that, the optimal dark adaptation time when performing ERG's, should be at least 20 min in conscious Miniature Schnauzer dogs.
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Affiliation(s)
- Hyung-Ah Yu
- Department of Veterinary Surgery and Ophthalmology, College of Veterinary Medicine and BK21 Program for Veterinary Science, Seoul National University, Seoul 151-742, Korea
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MacKay RJ. Brain injury after head trauma: pathophysiology, diagnosis, and treatment. Vet Clin North Am Equine Pract 2004; 20:199-216. [PMID: 15062465 DOI: 10.1016/j.cveq.2003.11.006] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Brain injury after impact to the head is due to both immediate mechanical effects and delayed responses of neural tissues. In horses, traumatic brain injury occurs in three main settings: (1) poll impact in horses that flip over backwards; (2) frontal/parietal impact in horses that run into a fixed object, and (3) injury to the vestibular apparatus secondary to temporohyoid osteoarthropathy. Distinct forebrain, vestibular, midbrain, hindbrain, or multifocal syndromes may be encountered in horses with traumatic brain injury. The most important components of treatment are those consistent with principles of "evidence-based medicine". Accordingly,secondary brain injury can most effectively be prevented by establishing normal blood pressure, temperature, blood glucose concentration, and tissue oxygenation. Pain must be controlled and brain swelling may be treated with infusions of hypertonic saline or mannitol. Surgical procedures, including unilateral hyoid bone transaction or elevation of skull fracture fragments, are indicated in selected cases. Optional additional treatments include use of anti-oxidants, conventional doses of corticosteroids, magnesium sulfate and drainage of CSE There is no indication for the use of massive doses of methyl prednisolone sodium succinate.
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Affiliation(s)
- Robert J MacKay
- Department of Large Animal Clinical Sciences, University of Florida, PO Box 100136, 2015 SW 16th Avenue, Room VH-136, Gainesville, FL 32610, USA.
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