[Show abstract][Hide abstract] ABSTRACT: The purpose of this study was to investigate the effects of refractive error on canine visual evoked potentials with pattern stimulation (P-VEP). Six normal beagle dogs were used. The refractive power of the recorded eyes was measured by skiascopy. The refractive power was corrected to -4 diopters (D) to +2 D using contact lens. P-VEP was recorded at each refractive power. The stimulus pattern size and distance were 50.3 arc-min and 50 cm. The P100 appeared at almost 100 msec at -2 D (at which the stimulus monitor was in focus). There was significant prolongation of the P100 implicit time at -4, -3, 0 and +1 D compared with -2 D, respectively. We concluded that the refractive power of the eye affected the P100 implicit time in canine P-VEP recording.
Preview · Article · Dec 2015 · Journal of Veterinary Medical Science
[Show abstract][Hide abstract] ABSTRACT: The purpose of this study was to evaluate the dark adaptation time in canine
electroretinography (ERG) using a contact lens electrode with a built-in LED. Twelve eyes
of six normal laboratory beagle dogs were used and exposed to steady room light at 500 lux
for 30 min for light adaption. ERG was recorded at different time points during dark
adaptation in sedated and light-adapted beagles. The stimulus intensity was 0.0096
cd/m2/sec. The b-wave amplitude increased significantly until 25 min of dark
adaptation, whereas no significant changes in amplitudes were observed after 30 min. Dark
adaptation for more than 25 min would be necessary for accurate ERG in canine ERG using a
contact lens electrode with a built-in LED.
Preview · Article · Jun 2015 · Journal of Veterinary Medical Science
[Show abstract][Hide abstract] ABSTRACT: The purpose of this study was to investigate the effects of sevoflurane concentration on canine visual evoked potentials with pattern stimulation (P-VEPs). Six clinically normal laboratory-beagle dogs were used. The minimum alveolar concentration (MAC) of sevoflurane was detected from all subjects by tail clamp method. The refractive power of the right eyes of all subjects was corrected to −2 diopters after skiascopy. For P-VEP recording, the recording and reference electrode were positioned at inion and nasion, respectively, and the earth electrode was positioned on the inner surface. To grasp the state of CNS suppression objectively, the bispectral index (BIS) value was used. The stimulus pattern size and distance for VEP recording were constant, 50.3 arc-min and 50 cm, respectively. P-VEPs and BIS values were recorded under sevoflurane in oxygen inhalational anesthesia at 0.5, 1.0, 1.5, 2.0, 2.5 and 2.75 sevoflurane MAC. For analysis of P-VEP, the P100 implicit time and
N75-P100 amplitude were estimated. P-VEPs were detected at 0.5 to 1.5 MAC in all dogs, and disappeared at 2.0 MAC in four dogs and at 2.5 and 2.75 MAC in one dog each. The BIS value decreased with increasing sevoflurane MAC, and burst suppression began to appear from 1.5 MAC. There was no significant change in P100 implicit time and N75-P100 amplitude with any concentration of sevoflurane. At concentrations around 1.5 MAC, which are used routinely to immobilize dogs, sevoflurane showed no effect on P-VEP.
Full-text · Article · Nov 2014 · Journal of Veterinary Medical Science
[Show abstract][Hide abstract] ABSTRACT: Electroretinography (ERG) is a well established diagnostic examination to evaluate retinal function objectively. In this study, ERG in Beagle dogs, which are popular as an experimental animal, was performed to determine the normal range of ERG and differences between the left and right eyes. ERGs, rod, combined rod-cone, single-flash cone and 30 Hz flicker responses, were recorded with an LED-electrode from 43 Beagle dogs under sedation, and the subjects were divided into young (< 1 year old), adult (1 ~ 5 years old), and senile groups (≥ 6 years old). The normal ranges of ERG were obtained, and significant differences in b-wave amplitude and b/a ratio of combined rod-cone response were found between the young and adult groups, and young and senile groups. No significant differences were found between left and right eyes. ERG in Beagle dog differed by age group, because of age-related retinal changes. Thus, we propose that normal ERG ranges should be determined by age groups in each clinic and laboratory with its own equipment, because each clinic and laboratory usually have different ERG system or protocol for ERG test.
Full-text · Article · Feb 2013 · Journal of veterinary science (Suwŏn-si, Korea)
[Show abstract][Hide abstract] ABSTRACT: We examined the refractive value in healthy Beagles by skiascopy. The mean refractive value of 54 eyes of 27 Beagles was 0.08 ± 0.87 (mean ± SD) diopters (D). The numbers of eyes defined as having emmetropia, myopia and hyperopia were 34, 8 and 12, respectively. Anisometropia was detected in 4 dogs. The mean refractive values in the 3-6-year-old and 8-9-year-old groups were 0.26 ± 0.84 and -0.29 ± 0.82 D, respectively, with a significant difference between the two groups (P<0.05).
No preview · Article · Feb 2011 · Journal of Veterinary Medical Science
[Show abstract][Hide abstract] ABSTRACT: The aim of this research was to evaluate the changes in the response of pattern-stimulated visual evoked potential (pVEP) with different pattern size, and demonstrate visual acuity from the minimum visual angle. pVEP was recorded from both eyes of six healthy beagles. Prior to pVEP recording, the dogs were sedated, and a traction fiber was used to prevent the eye from rolling down. The stimulator was set 30 cm from the subject's eye. Pattern reversal frequency of the stimulating monitor was 3 rev/sec, and pattern size was set at seven levels; 14-364 arc-min (1.2-31.4 mm). Amplitude of the P100 component was evaluated, and visual acuity was calculated from the minimum visual angle to obtain a pVEP response. A pVEP response (2.3-3.1 µV) was obtained from all subjects. The P100 component was detectable in 3 eyes with a check size of 14 arc-min and 7 eyes with 28 arc-min, and the component was undetectable with 14 arc-min in all subjects in which it was undetectable with 28 arc-min. From the minimum level to obtain the P100 component, the subjects' visual acuity was extrapolated as 0.54-2.14 cycles per degree. We demonstrated the change in P100 component with check size. However, our technique was inadequate to examine visual acuity because the subject's refractive index was ignored. We suggest that, with further study, pVEP with different check sizes would be applicable for canine visual acuity examination.
No preview · Article · Nov 2010 · Journal of Veterinary Medical Science
[Show abstract][Hide abstract] ABSTRACT: To investigate disease in the fellow eye, and consider the relation to rhegmatogenous retinal detachment (RRD) in Shih-Tzus.
The fellow eyes of 49 Shih-Tzus (27 male, 22 female; median age: 6.8 years) with unilateral RRD diagnosed by funduscopy or ultrasonography at Rakuno Gakuen University Teaching Animal Hospital were assessed in this study.
Ophthalmic examinations (including menace response, pupillary light reflex, slit-lamp biomicroscopy, and funduscopy) were performed in the subjects. Electroretinography was performed in 12 eyes that developed retinal degeneration. Maximum follow-up period was 42 months.
Cataracts and vitreous opacity were observed in 26 (53%) and 32 eyes (65%), respectively, by slit-lamp biomicroscopy. Retinal degeneration with various degrees of hyper-reflectivity of the tapetal fundus and/or attenuation of retinal vessels was observed in 35 eyes (71%) on funduscopy. A reduction of amplitude in rod, standard combined and 30 Hz flicker electroretinogram was detected in 5 (42%), 10 (83%), and 6 eyes (50%), respectively. During the follow-up period, RRD was detected in six eyes.
Retinal degeneration was frequently detected by funduscopy and electroretinograms in the fellow eye in Shih-Tzus with RRD. In our subjects, vitreous degeneration was also observed frequently. It has been reported that peripheral retinal degeneration is one of the causes of RRD associated with vitreous degeneration in humans. We assume that primary retinal degeneration with secondary vitreous degeneration is one of the causes of RRD in Shih-Tzus.
No preview · Article · Sep 2010 · Veterinary Ophthalmology
[Show abstract][Hide abstract] ABSTRACT: Manganese deficiency results in neurological and skeletal defects, together with ultrastructural disarrangement of the retina in rats. Wild birds show a range of Mn concentrations in their tissues, including the liver, raising the possibility of Mn-related disorders in the wild. Electroretinography (ERG) provides a useful noninvasive approach to evaluate visual function. This method is especially useful in birds, as objective analysis of them is very difficult, while they have well-developed vision. In this study, we carried out a convenient and reliable ERG recording using a contact lens electrode with a built-in light source (LED electrode) of Japanese quail (Coturnix coturnix japonica) fed a Mn-deficient diet. After 10 min light adaptation, single-flash and flicker cone responses were reproducibly recorded to cause an intensity-dependent increase in amplitude of both a-wave and b-wave in single-flash ERG. Mn-deficient feeding markedly decreased the Mn concentration in the liver by almost half in 3 to 6 weeks, followed by body weight loss in 13 to 15 weeks. Implicit time of a-wave and b-wave cone response by single-flash stimulation was significantly delayed in quail with a Mn depletion from 3 to 6 weeks. Every cone response of the Mn-deprived quail had a tendency to decrease amplitude. The ultrastructure of cone photoreceptor cells was disorganized by Mn deficiency, including changes in outer segment discs of photoreceptor cells. These results suggest the essential role of Mn in the integrity of the retinal function of birds.
Full-text · Article · Mar 2008 · Journal of Veterinary Medical Science
[Show abstract][Hide abstract] ABSTRACT: The purpose of this study was to determine the effects of cataract stage, lens-induced uveitis and cataract removal on the electroretinogram (ERG) of dogs with cataract.
Fifty-seven dogs diagnosed with unilateral or bilateral cataract whose ERG was recorded at Rakuno Gakuen University Teaching Animal Hospital from 2001 to 2004.
Four responses were recorded during the ERG: rod ERG, standard combined ERG, single-flash cone ERG and 30-Hz flicker ERG. Cataracts were divided into four stages: incipient, immature, mature and hypermature, and with or without lens induced uveitis (LIU). Noncataractous eyes of dogs with unilateral cataract were used as the control. We compared ERG amplitude, implicit time, and the b- to a-wave amplitude ratio of cataractous vs. noncataractous eyes, preoperative vs. postoperative cataractous eyes, and cataractous eyes with and without LIU.
No significant difference was found in ERG amplitude between incipient, immature and hypermature cataractous eyes, while in mature cataractous eyes decreased amplitude was confirmed in all responses compared with control eyes. However, no significant difference in b/a ratio was found at any stage of cataract. In postoperative eyes, increased amplitude was recorded in all responses compared to preoperative values. In eyes with LIU a decreased amplitude in the rod ERG and b-wave of standard combined ERG was recorded and, furthermore, a significant decline was confirmed in b/a ratio.
ERG values were influenced by cataract stage and LIU. LIU was associated with a reduction in the b/a ratio.
[Show abstract][Hide abstract] ABSTRACT: In dogs, a variety of diseases of the retina and choroid have been reported, either separately or concomitantly; however, the canine choroid is difficult to evaluate by veterinary techniques currently available. Indocyanine green (ICG) angiography is widely used in human ophthalmology, but has not been investigated for use in canine ophthalmology. The aim of this study was to apply a new approach to ICG angiography and compare the resulting angiograms with fluorescein (FLUO) angiograms of the ocular fundus in dogs. With a fundus camera equipped with an infrared-sensitive charged coupled device (CCD), we performed angiography on eight healthy beagles under inhalation anesthesia. ICG angiography enabled clear visualization of the choroidal vasculature, whereas FLUO angiography showed only the retinal vessels. At 8.4 +/- 3.6 sec after administration of ICG dye into the cephalic vein, the choroidal arteries could be seen extending radially from the optic disc, then the choroidal veins became apparent at 10.2 +/- 4.1 sec, coursing alongside the choroidal arteries. Gradual fading of the choroidal vessels began 13.2 +/- 2.2 min after the dye was administered, and overall diffuse fluorescence of the fundus appeared. Diffuse fluorescence of the fundus continued after the choroidal vessels and optic disc faded at about 58.3 +/- 5.3 min from administration of the dye. In conclusion, ICG angiography provides clear resolution and is reliable and simple, thus offering promise as a diagnostic aid for clinical evaluation of the choroid in dogs.
Full-text · Article · Jun 2007 · Journal of Veterinary Medical Science
[Show abstract][Hide abstract] ABSTRACT: We evaluated the efficacy of prophylactic antiglaucoma therapy with timolol maleate ophthalmic solution dis-solved in thermosetting gel in canine primary glaucoma. In the non-treated group (n=23), all dogs had con-firmed glaucoma in the other eye within 24 months of the diagno-sis of glaucoma in the first eye. In the treat-ed group (n=19), however, 53% of dogs had confirmed glaucoma in the other eye by 36 months after diagno-sis in the first eye. The incidence in the treated group was significantly (P<0.01) lower than that in the non-treated group. Dogs in the non-treated group developed glaucoma after a median of 7.7 months, whereas dog sin the treated group developed glaucoma a median of 18.7 months after theonset of glaucoma in the first eye. The median time until the onset of glaucoma in the second eye in the treated group was significantly (P<0.01) longer than that in the non-treated group. This data suggest that prophylactic antiglaucoma therapy with timolol maleate ophthalmic solution dissolved in thermosetting gel is useful for the second eye in canine primary glaucoma.
[Show abstract][Hide abstract] ABSTRACT: It is difficult to detect discrete cone function with the present conventional electroretinography (ERG) examination. In this study, we developed contact electrodes with a built-in color (red (644 nm), green (525 nm), or blue (470 nm)) light source (color LED-electrode), and evaluated an experimental model of digoxin in the dog. First, 17 normal Beagle dogs were used to determine which electrode works well for color ERG measurement on dogs. Then, color ERG was performed on seven normal Beagle dogs at various points during a 14-day period of digoxin administration. A single daily dose of 0.0125 mg/kg/day, which is within the recommended oral maintenance dosage range for dogs, was administered orally for 2 weeks. Ophthalmic examination, measurement of plasma concentration of digoxin, and color ERG examination were performed. On first examination, amplitudes of all responses were significantly (P < 0.01) lower with the red, than with the blue and green electrodes during ERG recording. In ERG using the red electrode, the standard deviation was large. According to these preliminary results, the red electrode was not used in the experimental dog model with digoxin. In the digoxin administrated animals, no significant change was observed in the ophthalmic examination findings. The digoxin level increased steadily throughout the dosing period but was always within the therapeutic range for dogs. In rod ERG, no abnormalities were detected with any electrode. In standard combined ERG, decreased amplitude of the a-wave was detected with every electrode. In single flash cone ERG, prolongation of implicit time was detected by color ERG with the blue and green electrodes. In 30-Hz flicker ERG, decreased amplitude was detected only by color ERG with the blue electrode. The decreased amplitude and prolonged implicit time recovered after termination of digoxin administration. Cone dysfunction induced by digoxin in the dog was revealed by multicolor ERG using blue and green LED-electrodes. Multi-color ERG was useful for detecting cone type-specific dysfunction in the dog.
No preview · Article · Nov 2005 · Veterinary Ophthalmology
[Show abstract][Hide abstract] ABSTRACT: Electroretinography (ERG) is an effective method for the diagnosis of retinal disease. In the dog, dependable ERG recording is difficult without the use of an expensive device like a Ganzfeld full-field stimulator. The International Society for Clinical Electrophysiology of Vision has defined the standard flash stimulus condition (SF) and evaluation of the retina using the b/a ratio in humans. In dogs, evaluation using the b/a ratio has not been reported, whereas the intensity of SF has been defined. In this study, we performed a convenient ERG recording method using a contact lens electrode with a built-in light source (LED-electrode), and confirmed SF as reported previously. ERG recordings were performed on 15 healthy beagle dogs under sedation. We performed bilateral ERG at 12 different intensities after 30 min dark adaptation. After 10 min light adaptation, we recorded single flash cone and flicker cone response using the SF determined in this study. In this study, SF of 3.0 cd/m(2)/sec (6,000 cd/m(2), 0.5 msec) resulted in b/a=2. The intensity for rod response that recorded only the b-wave was 0.0096 cd/m(2)/sec (80 cd/m(2), 0.12 msec). We could achieve ERG for each response easily and smoothly under sedation, and without general anesthesia. Using an LED-electrode, we could perform more quantitative and reproducible ERG examinations than with traditional methods. We propose that the b/a ratio is the most useful parameter in ERG reporting for evaluating retinal function.
Full-text · Article · Jun 2005 · Journal of Veterinary Medical Science
[Show abstract][Hide abstract] ABSTRACT: The anesthetic sparring and cardiovascular effects produced by midazolam 0.8 mg/ml-ketamine 40 mg/ml-medetomidine 0.05 mg/ml (0.025 ml/kg/hr) drug infusion during sevoflurane in oxygen (MKM-OS) anesthesia was determined in healthy horses. The anesthetic sparring effects of MKM-OS were assessed in 6 healthy thoroughbred horses in which the right carotid artery was surgically relocated to a subcutaneous position. All horses were intubated and ventilated with oxygen using intermittent positive pressure ventilation (IPPV). The end-tidal concentration of sevoflurane (ET(SEV)) required to maintain surgical anesthesia was approximately 1.7%. Heart rate and mean arterial blood pressure averaged 23-41 beats/min and 70-112 mmHg, respectively. All horses stood between 23-44 min after the cessation of all anesthetic drugs. The cardiovascular effects of MKM-OS anesthesia were evaluated in 5 healthy thoroughbred horses ventilated using IPPV. Anesthesia was maintained for 4 hr at an ET(SEV) of 1.7%. Each horse was studied during left lateral (LR) and dorsal recumbency (DR) with a minimum interval between evaluations of 1 month. Cardiac output and cardiac index were maintained between 70-80% of baseline values during LR and 65-70% of baseline values during DR. Stroke volume was maintained between 75-85% of baseline values during LR and 60-70% of baseline values during DR. Systemic vascular resistance was not different from baseline values regardless of position. MKM-OS anesthesia may be useful for prolonged equine surgery because of its minimal cardiovascular depression in both of lateral and dorsal recumbency.
No preview · Article · May 2005 · Journal of Veterinary Medical Science
[Show abstract][Hide abstract] ABSTRACT: Axial correction was performed surgically in two miniature dachshunds presenting with lateral patellar dislocation and limping caused by pes varus. Pes varus had resulted from asymmetric closure of the physis of the distal tibia. Prior to surgery, osteotomy was simulated by measuring X-ray films to determine the distance required for the wedge opening. Transverse-opening wedge osteotomy was performed on the medial side of the distal tibia, and beta-tricalcium phosphate (beta-TCP) was inserted in a wedge shape into the area created by the cuneiform osteotomy. Finally, the tibia was fixed by a veterinary 1.5/2.0-mm T-plate. Both dogs were able to walk a few days after surgery, and the lateral dislocation of the patella normalized almost completely in about one month. At two months, X-ray films showed that the implant had remained in position without any dislocation, and the beta-TCP had fused with the surrounding bone.
No preview · Article · May 2005 · Journal of Veterinary Medical Science
[Show abstract][Hide abstract] ABSTRACT: Nipradilol is an alpha(1), beta-blocker with milder side effects than other beta-blockers used in humans. In this study the effects of nipradilol were compared with those of timolol maleate in dogs. Twelve clinically normal dogs (nine mongrels, two beagles, and one Akita) were used. We applied 0.25% nipradilol or 0.5% timolol maleate drops for a period of 28 days. Intraocular pressure (IOP) was measured before and after administration on the 2nd, 4th, 7th, 14th, 21st and 28th day. Blood pressure, pulse rate and coefficient of aqueous outflow (C-value) were also measured before and after administration on the 7th, 14th, 21st and 28th day. Both nipradilol and timolol maleate significantly lowered IOP from the 2nd day to the end of the study period. Nipradilol lowered IOP to an equivalent degree to timolol maleate. There was no significant change in blood pressure and pulse rate throughout the study period with administration of nipradilol. C-value showed a significant rise from the 14th day with administration of nipradilol, while it did not show any significant change during the study period with administration of timolol maleate. The reduction of IOP by nipradilol was similar to that by an existing beta-adrenergic antagonist, timolol maleate, but nipradilol was associated with fewer systemic side effects in dogs. Nipradilol appears to be a useful drug for treatment of glaucoma in dogs.
No preview · Article · May 2004 · Veterinary Ophthalmology
[Show abstract][Hide abstract] ABSTRACT: Screw and laser (SL) column by making screw threads and forming small holes using laser irradiation on the base metal and conventional beads coating (BC) columns were embedded into the shaft of canine femurs, and compared the implant fixation to the host bone. The interfacial strength in SL columns was almost equivalent as BC columns, and bone-column contact rate was higher than BC columns significantly at twelve weeks after implantation. The newly devised SL surface had almost equivalent bone fixation strength comparable to the conventional BC surface. Also, this surface should provide a useful porous surface for use in artificial joints since there is no risk of surface structure detachment.
No preview · Article · Apr 2004 · Journal of Veterinary Medical Science
[Show abstract][Hide abstract] ABSTRACT: Intravenous injections (IV) of propionyl-promazine (0.05mg/kg) as pre-medication followed by N injections of either propofol 6 mg/kg (group PRP-P, n=30); ketamine 5 mg/kg (group PRP-K, n=30); or thiopental 12.5mg/kg (group PRP-T, n=30) as induction agents were carried out on 90 dogs. Anesthesia was maintained by 50% nitrous oxide-50% oxygen-sevoflurane. The end-tidal concentration of sevoflurane during surgery ranged between 2.2 and 2.3% in PRP-P, between 2.0 and 2.1% in PRP-K, and between 1.9 and 2.1% in PRP-T, with no statistical difference among groups. In PRP-K, 7% of the dogs experienced transient convulsions after ketamine administration, and laryngeal reflex during intubations occurred in a high percentage (80%). Incidences of transient apnea after intubation were 50% in PRP-P, 27% in PRP-K, and 40% in PRP-T, respectively. During anesthesia, because of such respiratory depression conditions as apnea and hypercapnia, controlled ventilation was required in 9 dogs (30%) in PRP-P, 4 dogs (13%) in PRP-K, and 10 dogs (33%) in PRP-T. Body temperature dropped with anesthetic time. In all groups, heart rate remained stable at 120-135 bpm. Moderate treatable hypotension occurred in 5 dogs (17%) in PRP-P, 8 dogs (27%) in PRP-K, and 5 dogs (17%) in PRP-T. Recovery from anesthesia was quiet and smooth in all dogs except for PRP-T dogs.In conclusion, PRP-P, PRP-K, and PRP-T are useful in combinations for inhalation anesthesia in clinically healthy dogs. But attention should be paid to the influence of laryngeal reflex and convulsion during induction with PRP-K and to delayed recovery when PRP-T is used.
[Show abstract][Hide abstract] ABSTRACT: The anesthetic effects of total intravenous anesthesia with propofol and fentanyl (PF-TIVA) were evaluated in 100 dogs. The dogs were pre-medicated by intravenous injections (N) of either 0.05mg/kg propionyl-promazine, 0.25mg/kg droperidol, 0.3mg/kg midazolam or 5μg/kg medetomidine. Surgical anesthesia was induced with propofol, and fenantyl was infused continuously at a rate of 0.2μg/kg/min following 2μg/kg bolus IV. The propofol infusion rate was controlled to maintain surgical anesthesia. Requirement infusion rate of propofol infusion was significantly lower in dogs pre-medicated with medetomidine (0.2-0.3mg/kg/min, P<0.001) than in the other animals (0.3-0.4mg/kg/min). During PF-TIVA, controlled ventilation was necessary in 41 dogs (41%). Body temperature decreased below 36.0°C in 36 dogs 36%. Heart rate was significantlylower in dogs pre-medicated with medetomidine (70-80 bpm, P<0.001) than in dogs given some other premedication (80-120 bpm). Moderate, treatable hypotension occurred in 19 dogs (19%). Recovery from PFTIVA was very quiet and smooth. In conclusion, PF-TIVA was successful in major surgery in dogs.