Toshiro Mori

Incomplete congenital stationary night blindness: Electroretinogram c-wave and electrooculogram light rise

Three cases of congenital stationary night blindness are reported. In all patients a negative electroretinogram was recorded by single bright flash stimulation and changed to positive on sequential reduction of the stimulus intensities. Oscillatory potentials were recognized. Biphasic dark adaptation curves and moderate elevation of the relative logarithmic final threshold of dark adaptation were also found. Values of critical flicker fusion frequency were reduced to a mild or moderate extent. VEP latency was prolonged beyond the normal range in two cases. In all three the electroretinogram c-wave was extinguished despite a normal electrooculogram light-dark ratio. It is hypothesized that in congenital stationary night blindness some disorder may exist in the apical membrane of the retinal pigment epithelium but not in the basal membrane in view of dissociation between the c-wave response and the light rise in the electrooculogram.

Combined photic and nonphotic electro-oculographic responses in the clinical evaluation of the retinal pigment epithelium.

In an attempt to simplify the recording technique in electrophysiologic evaluation of the retinal pigment epithelium, we combined the electro-oculographic light rise, hyperosmolarity and acetazolamide responses in a single recording session. Recordings were performed in six normal subjects and in seven patients with diabetic retinopathy or retinitis pigmentosa. In the patients with background diabetic retinopathy, the hyperosmolarity responses were slightly reduced, while the acetazolamide response and the light rise was normal. In the patients with proliferative diabetic retinopathy, the hyperosmolarity response and light rise were remarkably reduced, while the acetazolamide response was normal. In the patients with retinitis pigmentosa, the hyperosmolarity response and light rise were decreased, while the acetazolamide response was normal. Despite a small study population, we concluded that the clinical results from our combined recording protocol were essentially the same as those reported for each response separately. Because this recording technique simplifies electrophysiologic evaluation of the retinal pigment epithelium, it may help clarify the mechanisms or localization of retinochoroidal and pigment epithelial diseases.

Electroretinogram c-wave and slow PIII of the rabbit: Changes in peak time and amplitude under various stimulus durations

Changes in peak time and amplitude of the direct current registered c-wave of the electroretinogram of the albino rabbit were investigated with various stimuli of duration ranging from 0.25 to 10 sec. The stimulus intensity was 500 lux at the surface of the cornea. Slow PIII was isolated by administrations of sodium iodate and sodium aspartate.The peak time of the c-wave was longer than that of the slow PIII in the range of stimulus duration less than 3.5 sec, but peak times were almost the same in the range above 3.5 sec. The amplitude of the c-wave at peak was larger than the corresponding amplitude of the slow PIII in the range less than 1 sec, but the slow PIII became larger than the c-wave at more than 1 sec. For stimuli less than 4 sec, the smaller the stimulus duration, the smaller was the negative slow PIII which affected the height of the c-wave.We conclude that in order to minimize the influence of the slow PIII on the c-wave, the duration of stimuli with intensity of 500 lux for recording the c-wave of the rabbit should be less than 4 sec.

Impairment of convergence due to a lesion in the rostral part of the superior colliculus

We report a 28-year-old male suffering from convergence insufficiency due to a unilateral lesion in the rostral part of the superior colliculus (SC). The patient visited the emergency clinic complaining of vertigo. Cerebral CT revealed a high-density area in the left SC. Head MRI showed swelling in the rostal part of the left SC. No abnormalities were detected elsewhere. The present case supports data from animal experiments suggesting that the rostral SC participates in convergence.

ERG c-Wave at the Early Stage of Diabetic Retinopathy

The ERG, especially the DC-registered c-waye, and EOG were examined in 13 patients with early stages of diabetic retinopathy. The amplitudes of the ERG a-, b-wave and oscillatory potentials and the EOG L/D ratio were almost normal in all cases. The c-wave amplitudes in the majority of the cases were also within the normal range, but in some cases they were supernormal during dark and light adaptation. However, two cases demonstrated considerably low amplitudes. Since no significant change was observed in c-wave and EOG in the early stage of diabetic retinopathy, it is suggested that the effect of the lesion of the inner retina in diabetic retinopathy on the c-wave appears later than that on the oscillatory potentials.

The effect of β-blocker on ERG c-wave of the rabbit

The toxicity of β-blocker, Befunolol HCl (BFE), to the retinal pigment epithelium was investigated electrophysiologically. Rabbit in vivo ERG b- and c-waves were recorded after intravitreal injections of 0.1 ml of 0.25, 1, 2, 4, 6 and 10% BFE solutions with osmolalities of 304, 340, 383, 432, 493 and 618 mOsm repsectively. Phosphate solutions with osmotic pressure corresponding to the BFE solutions were injected as control.In eyes injected with 0.25% BFE, amplitude of either b- and c-waves were unchanged for 60 min, while in eyes injected with BFE with a higher concentration than 1%, the b-waves attenuated but the c-waves enhanced in proportion to the BFE concentrations.In the control group, the b-waves attenuated and the c-waves enhanced by the injection of the high osmotic phosphate solutions up to 500 mOsm, which corresponded to the osmotic pressure of 6% BFE, but attenuated by the phosphate solutions higher than 600 mOsm.Based on the above result, no acute toxicity of BFE to the retina was suggested in dose of its therapeutic use. The attenuation of b-waves by BFE was likely due to the influence of osmotic pressure since no significant difference in the b-waves amplitudes was found between BFE and equimolar phosphate solutions. However, high concentration of BFE itself was suggested to exhibit an effect to enhance the c-wave because a manifest difference was observed in the c-wave amplitudes between the group at higher BFE concentrations and the correspond control group.

The Long-Term Observation of the ERG c-Wave and EOG in Cases of Postoperative Retinal Detachment

We reported the changes in the ERG c-wave in cases of pre- and postoperative retinal detachment at the 19th ISCEV Symposium in Zurich. The present study is the second in a series of electrophysiological investigations on the function of the pigment epithelium in retinal detachment. The ERG c-wave and EOG were recorded from 5 patients postoperatively who had undergone successful surgery 1–2 years earlier; the ERG a- and b-waves, visual acuity, visual field and fluorescein angiography were also examined. The DC-registered ERG c-waves were recorded through 20 minute dark- and 15 minute light-adaptation courses after 5 minute 1,000 Lux pre-adaptation. The intensity and duration of the light stimulus employed were 50 Lux and 10 seconds respectively. The EOG amplitudes were recorded and analyzed by a computerized semi-automatic EOG recorder.