Generally, we can not investigate the ocular fundus before the age of 21 days in the Caniidae. However, the canine ocular fundus should be examined and recorded as soon as possible for congenital or genetic disease control in the posterior part of the eye. Basically, it is preferable to investigate canine ocular fundi without general anaesthesia as a part of the examinations. The inner ocular pressure should be checked using a mydriatric agent topically applied. After the examination, miotics should be applied to prevent induced glaucoma. Chorioretinitis is frequently recorded in the immature Akita dog's eye. The condition seems to be an initial sign leading to cataract, depigmentation of the nose, eyelids and skin, and finally blindness.

To prevent tragedy in this Japanese native breed, we wish to stress again that the investigation of the ocular region should be carried out at an early age as in other Japanese native breeds, standard and small, such as the Shiba, Kishu, Hokkaido-Inu, and so on, and in retrievers and others. If a nationwide survey of the canine eye is realized, points to be checked and regular techniques should be standardized with similar projects in other developed countries.

Fundus photography (FP) and fluorescein angiography (FA) were performed using a fundus camera, Kowa RC-2 Model-621 for small animal use in rats and mice and Kowa RC-2 for veterinary use in rabbits.

FP in rats and FP and FA in rabbits were performed in a conscious state without anesthesia; FA in rats and FP and FA in mice, under general anesthesia.

The appropriate conditions for fundus photography were: 50W lighting at Flash No. 4 in albino rats and mice: and 50W lighting at Flash No. 2 in rabbits. The fundus photography in albino rabbits required a neutral density filter (ND-0.6), because an intensified retinal reflex interferred with photographing. On the other hand, in pigmented rats and mice, good photographs were obtained with 100W lighting.

The suitable conditions for fluorescein angiography were: injection of 0.4ml/kg of 10% fluorescein under 100W lighting in albino rats; 0.3ml/kg of 10% fluorescein under 100W lighting in pigmented rats; and 0.2ml/kg of fluorescein under 50W lighting at Flash No. 6 in albino or pigmented rabbits.

The present study was undertaken to confirm the suitability of techniques and procedures used for the recording of ERGs in the authors' laboratory. A single intravenous administration with 1% aqueous solution of chlorpromazine hydrochloride, at a dose of 10 mg/kg, was carried out on 3 adult male beagles. Electroretinograms (ERGs) were sequentially recorded by the standard operation procedure that has been routinely used in the laboratory.

All the animals showed a common tendency toward an extension of the peak latency time and a decrease in amplitude for a- and b- waves, recovering 48 hours after administration.

The trial revealed clear changes in the ERG reflecting the pharmacological effect of chlorpromazine in 3 dogs except for a little individual difference, and therefore the technique and procedure employed were considered suitable for obtaining reproducible data in routine use. Better restraint methods need to be developed and prevention of interference from myoelectricity also needs to be studied.

In order to study their use in toxicity studies, electroretinograms (ERGs) were measured in conscious beagles treated orally with ethambutol at a dosage of 500 mg/kg/day (250 mg/kg b.i.d.) for 7 days. The tapetum lucidum was discolored and ERGs showed slightly lowered amplitude or prolonged peak latency in the a-wave and b-wave. No remarkable changes were observed in behavior suggesting disorder of visual function. Tapetal discoloration did not change but the changes in the ERG recovered 4 weeks after withdrawal. To measure the ERG in conscious beagles it is necessary to keep the animals quiet because of interruption by the noise from moving eyes or legs. Our results indicated the possiblity of using ERGs in toxicity studies and the necessity of accumlating background data.

We investigated the electroretinogram (ERG) and visual evoked potential (VEP) in an electrophysiological visual function test in dogs.

Thirteen male beagles were given a mixed solution of xylazine and atropine sulfate subcutaneously to calm them down and to measure the ERG (a- and b-waves and oscillatory potentials) and VEP (F-VEP and PR-VEP). These waves were measured twice at intervals of 5 to 7 days to confirm the reproducibility of these parameters. It was possible to record oscillatory potentials with good reproducibility in the ERG, in addition to the a-waves and b-waves which are usually measured in animal studies. As for the VEP, F-VEPs induced by flash stimulation, which is usually used in animal studies, had poor reproducibility because the F-VEP depends on measuring conditions such as radiation volume. On the other hand, it was possible for PR-VEPs induced by pattern reversal stimulation to show good reproducibility in dogs, as in humans.

These findings suggest that oscillatory potentials in ERGs and PR-VEPs in VEPs can be used in electrophysiological visual function tests in dogs, in addition to the a-waves and b-waves of ERGs and F-VEPs which are usually adopted in electrophysiological visual function tests in animal studies.

To objectively evaluate the progress of injury caused by visual disorder-inducing drugs and recovery from injury in dogs, an electroretinogram (ERG) was taken without any general anesthetic agent, and the effects on the a-wave, b-wave, and oscillatory potential were examined.

Ethambutol and sodium iodate were used as visual disorder-inducing drugs. Each drug was dissolved in physiological saline (J. P. grade). Ethambutol was administered subcutaneously into the rear dorsal skin at a daily dose of 250 mg/kg for 4 consecutive weeks. Sodium iodate was injected into the cephalic vein of the foreleg once.

Electroretinography was performed without using any anesthetic or restricting the animals. ERGs were taken before administration, and on the 5th, 7th, 14th, 21st and 28th day of administration in the case of ethambutol, and before administration and 1, 3, 5, 24, 48 and 72 hours after administration in the case of sodium iodate, using a recorder for induced reactions. Photo-stimulation was carried out once for each ERG using a xenon lamp at a stimulating intensity of 20 joules 30 cm in front of the eye. The time constant was set at 0.3 and 0.003 sec. The fundus of each eye was examined at the time of the ERG.

With repeated subcutaneous administration of ethambutol, no clear changes in ERG were observed during the administration period, but decoloration of the tapetum lucidum was observed with funduscopy from the 5th day of administration.

In the case of single intravenous injection of sodium iodate, decreases in the amplitude of a- and b-waves appeared 1 hour after administration, and each wave reached its minimum 48 - 72 hours after administration, then gradually returned toward the baseline. Oscillatory potential showed changes similar to those of a- and b-waves, but the course of their recovery was not clear. In addition, partial discoloration of the tapetum lucidum was observed by funduscopy from 24 hours after administration.

This study was performed to determine the reproducibility of electroretinograms (ERGs) and the effects of anesthesia on the ERG.

Rats were held in the dark for 2 to 3 hours before examination. They were restrained under light ether anesthesia, and topical Benoxyl (0.4% oxybuprocaine hydrochloride) was applied topically to the eyes. A contact lens attached to a recording electrode was placed on the cornea. Ground and reference electrodes were placed on the ear and forehead, respectively. The "a" and "b" waves of ERG were elicited by a single Xenon flash of 0.6 joule at 30 cm from the surface of the eye, and were recorded using a Neuropack Four Mini (MEB-5304, NEC) with a sweep time of 20 msec/div., sensitivity of 200 μV/div., and high and low cuts of 1 kHz and 1 Hz.

The amplitudes and implicit times of "a" and "b" waves obtained from 22 rats were 446±55μV and 18.7±0.9 msec, and 971±116μV and 55.7±4.0 msec, respectively. The coefficient of variation was 12% for amplitude and 5 to 7% for implicit time, suggesting that implicit time was a more consistent parameter than the amplitude. The coefficients of variation of averages of "a" wave amplitudes and implicit times in 5 rats on 3 different days were less than 10%, suggesting acceptable reproducibility.

The effects of pentobarbital 40 mg/kg i.p. on ERG were determined in 5 rats. There were 6% and 20% decreases in amplitude, and 26% and 14% increases in implicit time of "a" and "b" waves, respectively, in pentobarbital-treated rats as compared with pretest values.

In addition, rats were also tested without anesthesia, and nearly steady ERGs could be obtained under one or above one hour dark adaptation.

This method provides relatively consistent amplitudes and implicit times of "a" and "b" waves, and is able to detect the effects of pentobarbital on the electroretinal activity. These data demonstrate that the ERG method is essential to determine electrophysiologically adverse effects of test compounds on the retina.

The corneal endothelia of 9 male beagles (age: 8∼9 months) were examined with a contact-type specular microscope under general anesthesia. The specular microscopy showed uniform-sized, hexagonal endothelia arranged regularly on the innermost layer of the cornea. Concerning the cell density (cells/mm²), no statistically significant difference was observed between the left and right eyes. The fluorescein staining during the corneal or slit-lamp examination of the anterior portion made it clear that there were no wounds on the surface of the cornea and no inflammation in the anterior chamber in any dog.