Biomedical subjects

A Tanikawa

Publications and source records attributed to A Tanikawa.

33 records · Page 2Linked to original sources

PubMed1999

Amplitude increase of the multifocal electroretinogram during light adaptation.

PURPOSE: To determine using the multifocal ERG technique whether there are any regional differences in the increase in the amplitude of cone electroretinograms (ERGs) during light adaptation. METHODS: Multifocal ERGs were recorded with the Visual Evoked Response Imaging System from five normal subjects. Thirty-seven hexagonal stimulus elements and a recording time of 60 seconds were used. After 20 minutes of dark adaptation, multifocal ERGs were repeatedly recorded every 2 minutes over a period of 16 minutes. The amplitudes of the multifocal ERGs at different eccentricities were compared during the 16 minutes of light adaptation. RESULTS: During the 16 minutes of light adaptation, the summed responses of the multifocal ERGs increased in amplitude an average of 36% and 47% for the negative and positive components, respectively. The magnitude of increase was minimal in the central retina at 22% and was significantly larger in the peripheral retina at 58%. The implicit time was slightly increased (<4%) with light adaptation, but there were no regional differences. CONCLUSIONS: The results demonstrated that there are topographic variations in the amplitude increase of cone ERGs during light adaptation. This topographic variation indicates that the mechanism for the increase must be based on known regional differences in the retina.

Adaptation, Ocular↗

PubMed1998

Focal macular electroretinograms before and after successful macular hole surgery.

PURPOSE: To report changes in focal macular electroretinograms before and after successful macular hole surgery and to discuss whether preoperative retinal function can predict postoperative visual acuity. METHODS: In this prospective study, 28 consecutive eyes of 28 patients underwent vitrectomy for stage 2 or 3 full-thickness idiopathic macular hole. Focal macular electroretinograms using a 4-degree stimulus spot were obtained in 24 eyes of 28 patients, and those using a 5-degree stimulus spot were obtained in 24 eyes of 28 patients, to evaluate preoperative and postoperative amplitude and implicit time of the b-wave. Visual acuity was measured preoperatively and postoperatively, and results were translated into logMAR (minimum angle of resolution) values. RESULTS: After successful macular hole closure, the b-wave amplitude increased in 23 of 24 eyes measured with the 4-degree stimulus spot and in 19 of 24 eyes measured with the 5-degree stimulus spot. Postoperative b-wave amplitude recorded with either stimulus spot correlated with postoperative corrected visual acuity. The b-wave implicit time decreased in 15 of 20 eyes measured with the 4-degree spot and in 13 of 23 eyes measured with the 5-degree spot. Preoperative b-wave implicit time measured with the 5-degree stimulus spot correlated significantly (P = .001) with postoperative corrected visual acuity. CONCLUSIONS: Qualitative change (implicit time) is more important than quantitative change (amplitude) in electroretinograms for predicting postoperative corrected visual acuity. The function of the retinal tissue surrounding the hole may affect visual outcome.

Adult↗

PubMed1998

Recording multifocal electroretinogram on and off responses in humans.

PURPOSE: To record the on and off responses of the multifocal photopic electroretinogram (ERG) from the human retina and to explore how each ERG component (a-, b-, and d-waves) changes at different retinal eccentricities. METHODS: Multifocal ERGs were recorded with the visual evoked response imaging system. Sixty-one densely packed stimulus elements were square wave-modulated between stimulus on and stimulus off, according to a binary m-sequence at a rate of 4.7 Hz under a constant background illumination. The ERGs were recorded with a bipolar Burian-Allen bipolar contact lens electrode from five normal subjects. Response densities (amplitude per retinal area) were calculated for five different eccentric rings. RESULTS: The response densities for all components (a-, b-, and d-waves) decreased with increasing retinal eccentricities. The ratio of the d-wave to b-wave amplitudes was minimal in the central retina and increased toward the periphery. The ratio of a-wave to b-wave amplitudes also increased toward the peripheral retina. CONCLUSIONS: These results demonstrate that the on and off responses of the human cone ERGs have different spatial distributions across the human retina, and they suggest a change in the photopic retinal circuitry with increasing retinal eccentricities.

Adult↗

PubMed1998

Effect of glutamate analogues and inhibitory neurotransmitters on the electroretinograms elicited by random sequence stimuli in rabbits.

OBJECTIVE: To study the origin of the different components of the electroretinogram (ERG) elicited by a random binary m-sequence stimulus. METHODS: Electroretinograms were recorded from pigmented rabbits before and after the injection of glutamate analogues (2-amino-4-phosphono-butyric acid [APB; DL form] and cis-2,3-piperidine-dicarboxylic acid [PDA]) and inhibitory neurotransmitters (glycine and gamma-aminobutyric acid [GABA]) to abolish the contribution of different cell types to the ERG. Two types of stimuli were used: conventional full-field stimulation with short- and long-duration flashes and a random binary m-sequence of flashes designed to mimic the pseudorandom binary m-sequence stimulation used in the multifocal ERG technique. RESULTS: The effects of APB and PDA on the first-order kernel of the random ERGs were similar to those on the photopic short-flash ERG. Glycine and GABA minimized the oscillatory potentials (OPs) of the photopic ERGs, and also reduced the amplitude of the positive wave of the first-order kernel slightly but caused a large reduction in the amplitude of the second-order kernel. CONCLUSIONS: The data suggest that the ON and OFF bipolar cells contribute significantly to the photopic short-flash ERG, as previously shown, and to the first-order kernel of the responses elicited by the pseudorandom binary sequence stimuli. The second-order kernel and the OPs receive a strong contribution from the cells of the inner retinal layers.

Aminobutyrates↗

PubMed1997

Focal macular electroretinogram before and after drainage of macular subretinal hemorrhage.

PURPOSE: To record and evaluate change in preoperative and postoperative macular electroretinograms in patients undergoing surgical drainage of macular subretinal hemorrhage. METHODS: Five eyes of five patients with good visual acuity before onset of hemorrhage underwent vitrectomy between 3 and 14 days after developing hemorrhage, with drainage of submacular hemorrhage, using recombinant tissue plasminogen activator. The causes of subretinal hemorrhage were macroaneurysm in three eyes, age-related macular degeneration in one eye, and unknown in one eye. Visual acuity and macular electroretinograms were recorded preoperatively and postoperatively. RESULTS: In all eyes, preoperative electroretinographic response was remarkably reduced or not recordable. Postoperative visual acuity improved, and electroretinographic response recovered to about one half the amplitude of the fellow eye in every eye with a normal fellow eye. CONCLUSIONS: A nearly nonrecordable preoperative response on macular electroretinogram indicates severe dysfunction of the photoreceptors caused by the submacular hemorrhage. A postoperative recovered macular electroretinogram suggests that photoreceptor function is at least partially reversible with surgical intervention, including injection of recombinant tissue plasminogen activator into the subretinal space.

Aged↗

PubMed1997

Recording multifocal electroretinograms with fundus monitoring.

PURPOSE: To record multifocal electroretinograms (ERGs) with simultaneous fundus monitoring. METHODS: An infrared television fundus camera was used to monitor the fundus. A tightly packed array of 19 yellow light-emitting diodes (LEDs) was used as the stimulus source and LEDs were alternated between on and off according to a binary m-sequence at a rate of 75 Hz. The stimulus array subtended approximately 25 degrees of the visual angle. Multifocal ERGs were recorded with a Burian-Allen bipolar contact lens electrode from two normal subjects and a patient with macular dystrophy. RESULTS: When the center of the stimulus was positioned on the fovea, the amplitude of the response was largest at the fovea and decreased toward the peripheral retina; the response pattern corresponded to the spatial distribution of cone cells. When the center of the stimulus was positioned on the optic disc, the response at the optic disc was undetectable. A reliable multifocal ERG was obtained from a patient with macular dystrophy. CONCLUSIONS: This system made it possible to monitor the stimulus on the fundus and to adjust the stimulus to the correct retinal locations with exact focusing. The authors' findings indicate that this method especially can be useful in patients with poor fixation. In addition, the authors' results suggests that the stray light effect in the multifocal stimulus system is minimal if any.

Adult↗

PubMed1997

[Aging and the focal macular electroretinogram].

Focal macular electroretinograms (MERGs) were recorded with a fundus monitor through an infrared television fundus camera in 112 eyes of 112 normal subjects (68 males, 44 females), using three stimulus spots 5 degrees, 10 degrees, and 15 degrees in diameter. The amplitude and the implicit time of the a-wave, h-wave, and oscillatory potentials (OPs), and the ratio of amplitude of the b-wave to the a-wave (b/a ratio) at each stimulus spot were compared in terms of aging and sex. The amplitude of all components decreased significantly (p < 0.01-0.05) after the fifth decade, and there was a tendency for OPs to decrease more than the a-wave and b-wave. There was no significant effect of age on the h/a ratio and the implicit time of each component. The ratio of increase of amplitude to the enlargement of stimulus spot showed no significant changes with age. There was no significant difference in each component in terms of amplitude and implicit time with sex. The decrease of amplitude of all components after the fifth decade suggests aging of the macular cones. The tendency toward decreasing OPs also suggests aging of the inner retina in the macular region. The proportional changes of amplitude recorded with three different sizes of stimulus spots indicate that there is no significant effect of aging on the fovea, parafovea, or perifovea.

Adult↗

PubMed1997

[The effect of age on short-wavelength sensitive cone electroretinograms and long-and middle-wavelength sensitive cone electroretinograms].

We studied the effect of age on short-wavelength sensitive cone electroretinogram (S-cone ERG) and long-and middle-wavelength sensitive cone ERG (LM-cone ERG) using a contact lens electrode with a built-in light-emitting diode. We recorded ERGs in 31 pseudophakic subjects to avoid the effect of yellowing in human crystalline lens. The intensities of our stimuli were on the asymptote of the intensity-response curve. We performed linear regression analysis against age on the S-cone ERG b-wave (S-b), and the LM-cone ERG a-, b- and d-waves (LM-a, LM-b, LM-d). We found significant age-dependent reduction in the amplitude of S-b, LM-a, and LM-d, significant prolongation in the peak time of LM-b and LM-d, and significant increase in the b/a ratio of the LM-cone ERG, but no significant age correlation between the peak time of S-b and LM-a and the amplitude of the b-wave. Our results provide evidence that age-related changes in S- and LM-cone systems begin in the twenties in humans. Furthermore, a significant increase of the b/a ratio suggests that off-bipolar cells are more vulnerable to aging than on-bipolar cells.

Adult↗

PubMed1996

Occult macular dystrophy.

PURPOSE: Occult macular dystrophy is a hereditary macular dystrophy without any visible abnormality of the fundus or abnormality indicated by fluorescein angiography even when visual acuity is decreased. Normal full-field electroretinogram in both cone and rod components with abnormal focal macular cone electroretinogram is the key to diagnosing this disorder. The purpose of this study was to identify the function of the macular rods and to provide detailed clinical findings in occult macular dystrophy. METHODS: Thirteen patients from eight families were examined. The fundi of 12 patients were essentially normal (occult macular dystrophy), and the oldest patient in one family disclosed bull's eye maculopathy. In the 12 patients, including the patient with bull's eye maculopathy, the profiles of cone and rod absolute thresholds were performed across the 60-degree horizontal meridian of the posterior pole. RESULTS: All 12 patients showed cone sensitivity loss only in the macular area. Six relatively young patients revealed normal rod sensitivity, whereas six older patients showed borderline rod sensitivity or abnormal rod sensitivity in the macular area. CONCLUSIONS: The pathology of occult dystrophy involves either only the macular cone system or macular cone and rod systems without any visible abnormality. This difference of the pathology suggests a different clinical entity or a different stage of occult macular dystrophy.

Adolescent↗

PubMed1996

[Normal values of retinal response densities in multifocal electroretinogram].

Multifocal electroretinograms (ERG) were recorded from 21 normal eyes to investigate the spatial distribution and inter-individual variation of local cone responses. To compensate for the effect of refractive lenses, test distances were adjusted to obtain a constant magnification on the retina. Significant nasal-temporal asymmetry was observed near the fovea with higher response densities in the temporal retina along the horizontal meridian. No significant supero-inferior asymmetry was observed along the vertical meridian. The average coefficient variation (standard deviation/average) of retinal response density for all areas was 0.35. In the clinical application of the multifocal ERG these results must be taken into consideration.

Adult↗

PubMed1996

Electrophysiological findings in patients with Oguchi's disease.

Seven patients with Oguchi's disease were examined by conventional full-field rod and cone electroretinograms (ERGs), spectral characteristic studies with photopically matched short- and long-wavelength stimuli (3 of the 7 patients) and electrooculogram (EOG) (6 patients). ON and OFF photopic ERG responses, recorded with rectangular stimuli, in 3 patients were compared with those of 13 normal subjects and 13 patients with complete congenital stationary night blindness (CSNB). Conventional full-field ERGs recorded after 30 minutes of dark adaptation revealed absent rod, but essentially normal cone and flicker ERGs in all patients. With the dark-adapted standard flash ERG, the a-wave amplitude was significantly lower than normal in all patients. The spectral characteristic study indicated that the ERG recorded after 30 minutes of dark adaptation represented cone activity. The EOG was abnormal in all patients examined. The ON and OFF responses of the photopic ERG were normal in Oguchi's disease patients; however the ON responses were reduced in patients with complete CSNB. The absence of a rod a-wave, with the abnormal EOG, strongly suggests that the rod itself is abnormal in Oguchi's disease. This finding differs from the report by Carr and Gouras (1965) and Carr and Ripps (1967). The normal ON and OFF responses in the photopic ERGs of Oguchi's disease patients contrast with those of the complete CSNB patients in whom only the ON response is reduced.

Adolescent↗

PubMed1995

Blue light-emitting diode built-in contact lens electrode can record human S-cone electroretinogram.

PURPOSE: To develop a contact lens electrode with a built-in blue light-emitting diode (LED) to record the electroretinogram from short-wave sensitive-cone (S-cone) electroretinogram (ERG) in humans. METHODS: The ERG was recorded using the blue LED (450 nm) built-in electrode under a yellow background illumination from a slide projector in five normal subjects, a patient with blue cone monochromatism, and a patient with fundus albipunctatus. For comparison, the ERG was also recorded using a yellow LED (566 nm) built-in electrode under the same background illumination in the normal subjects. RESULTS: The amplitude and the peak time of the b-wave recorded with 3-Hz blue stimuli were 5.1 to 12.4 microV and 63 to 68 msec, respectively in normal subjects, 7.3 microV and 65 msec in the patient with blue cone monochromatism, and 11.4 microV and 65 msec in the patient with fundus albipunctatus. Normal subjects responded to neither 30-Hz blue stimuli nor 3-Hz yellow stimuli. CONCLUSIONS: Results indicate that the b-wave recorded with 3-Hz blue stimuli is elicited from the S-cone system. This simple technique is useful for testing the human blue cone system.

Adult↗

PubMed1995

Clinical evaluation of multifocal electroretinogram.

PURPOSE: To compare the multifocal electroretinogram (ERG) system to conventional ganzfeld and focal ERGs obtained from patients with known retinal diseases to assess its clinical applicability. METHODS: A multi-input system analysis was used to explore the field topography of ERG responses to local luminance modulation in patients with retinitis pigmentosa, pericentral pigmentary retinal dystrophy, branch retinal arterial occlusion, or idiopathic macular hole. RESULTS: The dysfunctional areas measured by multifocal ERG were compatible with those assumed by combined findings of ganzfeld and focal ERGs. However, the wave shapes of multifocal ERG in the retina with arterial occlusion differed from those of conventional focal ERG, suggesting that the negative and positive deflections shown in the first-order kernel of multifocal ERG may not correspond to conventional a- and b-waves of ERG. CONCLUSIONS: The multifocal ERG system is available for electroretinographic field mapping at the clinical level.

Adult↗

PubMedDate not supplied

Effect of age on short-wavelength sensitive cone electroretinogram and long- and middle-wavelength sensitive cone electroretinogram.

Using a light-emitting diode (LED) built-in contact lens electrode, we studied the effect of age on short-wavelength sensitive cone electroretinograms (S-cone ERG) and long- and middle-wavelength sensitive cone ERGs (LM-cone ERG). We recorded ERGs in 31 pseudophakic subjects to avoid the effect of yellowing in the human crystalline lens. The intensities of our stimuli were on the asymptote of the intensity-response curve. Linear regression analysis against age was carried out on the S-cone ERG b-wave, and the LM-cone ERG a-, b-, and d-waves. We found significant age-dependent reduction in the amplitude of the S-cone ERG b-wave, and the LM-cone ERG a- and d-waves, significant prolongation in the peak time of the S-cone b-wave and the LM-cone ERG b-wave, significant increase in the b/a ratio of the LM-cone ERG, but no significant age correlation between the LM-cone ERG a-wave and the amplitude of the b-wave. Our results provide evidence that age-related changes in S- and LM-cone systems begin in early adulthood in the human eye. A significant increase in the b/a ratio suggests that off-bipolar cells are more vulnerable to aging than on-bipolar cells.

Adult↗

PubMedDate not supplied

Amplitude decrease of photopic ERG b-wave at higher stimulus intensities in humans.

PURPOSE: The b-wave of the human photopic electroretinogram (ERG) elicited by a short-flash increases in amplitude with increasing stimulus intensities at lower stimulus levels, but then decreases at higher stimulus intensities. The purpose of the present study was to explore this phenomenon in more detail, using short- and long-flash stimuli. METHODS: The intensity-response functions of the b-wave elicited by short- and long-flashes were compared from threshold to higher stimulus intensities in 5 normal subjects. Short- and long-flash ERGs were elicited under rod-saturating background levels using white light-emitting diodes built into a contact lens electrode. RESULTS: Whereas the amplitude of the short-flash b-wave decreased at higher intensities, the amplitude of the long-flash ERG b-wave did not decrease but plateaued. The long-flash ERG d-wave or OFF-response decreased at higher stimulus levels as did the short-flash elicited b-wave. CONCLUSIONS: Because it is widely accepted that the b-wave and the OFF-response d-wave interact to produce a single positive response, our results suggest that the decrease in the b-wave amplitude at high stimulus intensity is caused by the decrease of the d-wave at the higher stimulus intensities.

Adaptation, Ocular↗