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Biomedical subjects

N Shiroyama

Publications and source records attributed to N Shiroyama.

14 recordsLinked to original sources
PubMed1993

Classification of aphakic cystoid macular edema with focal macular electroretinograms.

We compared the amplitude and implicit times of the a-waves, b-waves, and oscillatory potentials of the focal macular electroretinograms of 30 eyes with aphakic cystoid macular edema and the healthy fellow eyes. Ten affected eyes were characterized by reduced amplitudes of the oscillatory potentials with normal a-wave and b-wave responses (type 1). Nine affected eyes had both reduced amplitudes of the oscillatory potentials and the b-waves (type 2). Ten affected eyes were characterized by reduced amplitude of the oscillatory potentials, the a-waves, and the b-waves (type 3). One eye could not be classified. Visual acuities were as follows: type 1, 0.55 (20/36.4); type 2, 0.31 (20/64.5); and type 3, 0.12 (20/166.7). The mean time between cataract surgery and the electroretinographic testing was significantly longer for type 2 and 3 eyes than for type 1 eyes. The differences in the electroretinographic responses between the affected eye and the normal fellow eye suggested either an increased severity or the stage of the cystoid macular edema.

Aged↗
PubMed1993

[Peripheral polyneuropathy due to sarcoidosis in a patient with intrathoracic, ocular and skin lesions].

Sarcoidosis is a multisystem disorder of unknown etiology presenting most frequently with bilateral hilar lymphadenopathy (BHL), pulmonary infiltration, and ocular and skin lesions. Neurological manifestations are found in about 5% of patients with systemic sarcoidosis. We report the case of a 58-year-old woman with neurosarcoidosis manifesting as isolated, peripheral polyneuropathy. This is a rare neurological manifestation. Two years before admission, she was found to have an abnormal chest radiograph showing BHL, and pulmonary sarcoidosis was diagnosed by lung biopsy. Six months later, she noted facial erythematous lesions, and lupus pernio was confirmed by skin biopsy. Fifteen months before admission, she developed visual disturbance of the right eye caused by sarcoid-uveitis. Two months before admission, she complained of paresthesia and weakness of limbs. She was admitted for nerve-biopsy. Sural nerve biopsy revealed sarcoid granulomas in the epineurial space, periangitis and axonal degeneration. Neurologically, the diagnosis of mononeuritis multiplex without cranial nerve palsy was made. Treatment with 30 mg prednisolone daily was initiated, and neurological and extraneurological improvement was noticeable within two weeks of treatment. The dose was carefully lowered over several months.

Female↗
PubMed1993

Focal macular electroretinogram in X-linked congenital retinoschisis.

PURPOSE: To study macular function of X-linked congenital retinoschisis (CRS) by focal macular electroretinogram (MERG). METHODS: MERGs were recorded with 5 degrees, 10 degrees, and 15 degrees spots in 20 patients with CRS. Seventeen patients showed foveal schisis with little or no change in foveal fluorescein angiography (Group 1), and three patients showed advanced macular changes with nonspecific macular degeneration (Group 2). RESULTS: In Group 1, a-wave amplitudes were within the normal range, but b-waves and oscillatory potentials (OPs) had mean amplitudes significantly below those for normal control subjects. The mean b- to a-wave ratios, significantly lower than in normal eyes, decreased significantly with decreasing spot size. The implicit times of a-waves, b-waves, and OPs were significantly delayed. In Group 2, MERGs were nearly nondectable. CONCLUSIONS: The macular pathology of CSR exists mainly in the middle and inner retinal layers, disturbing the fovea more than the perifovea, whereas degeneration of photoreceptors progresses in more advanced stage.

Adolescent↗
PubMed1992

Fundus albipunctatus associated with cone dystrophy.

We describe five unrelated patients in whom the typical signs of fundus albipunctatus were accompanied by colour vision defects, bull's eye or similar macular lesions, and severely diminished full-field cone electroretinograms indicating widespread damage to cones outside the macula. All patients had noticed night blindness from childhood. Signs of retinitis punctata albescens, a disease of similar appearance but with characteristics resembling retinitis pigmentosa, were absent. We cannot be sure whether these patients represent a process of fundus albipunctatus or a distinct disease entity or a casual combination of fundus albipunctatus and cone dystrophy.

Adult↗
PubMed1990

Oscillatory potentials of local macular ERG in diabetic retinopathy.

The oscillatory potentials (OPs) in electroretinogram (ERG) have clinical values in measuring retinal functions of the early stage of diabetic retinopathy. However, OPs have, until now, been evaluated as components of total ERG recorded with a full field stimulus over the entire retina. Therefore, little information could be obtained about the macular condition (diabetic retinopathy). Using focal stimuli, we successfully recorded OPs in the human macular region. We modified our previously reported system for recording local macular ERG under the fundus monitor with an infrared television fundus camera. We evaluated macular OPs with simultaneously recorded a- and b-waves in many patients with diabetic retinopathy. In some kinds of early diabetic maculopathy, the macular OPs were selectively reduced, leaving the a- and b-waves intact. The macular OPs can be a valuable indicator in assessing the macular function in diabetic maculopathy.

Adult↗
PubMed1990

[Focal macular electroretinogram in high myopia].

To investigate early changes of the macula in eyes with myopia, we compared 66 eyes with high myopia with 76 normal eyes by recording focal macular electroretinogram (ERG). The eyes with high myopia were divided into two groups; eyes showing only tigroid fundus (group 1) and those associated with posterior staphyloma involving the macula (group 2). The visual acuity of groups 1 and 2 was 1, 0 or better and 0.8 or better, respectively. The amplitude of the a-wave, b-wave in group 1 was significantly smaller than that of normal eyes, however the peak latency was within the normal range. The amplitude of a-wave, b-wave and oscillatory potentials in group 2 was significantly smaller and the peak latency was significantly longer than those in group 1. The abnormal amplitude with normal peak latency in group 1 suggests some reduction of numbers of cones, which is considered to be an early pathologic change in the macula with high myopia. The more reduced amplitude with delayed peak latency in group 2 suggests that, in the advanced stage, the macular pathologic finding includes some quantitative damage as well as further reduction of macular cones.

Adolescent↗
PubMed1990

[Analysis of focal macular ERG in idiopathic central serous chorioretinopathy].

Focal macular electroretinogram (MERG), was analyzed in 33 patients with unilateral central serous chorioretinopathy (CSC) of recent onset. The stimulus spots were 5 degrees, 10 degrees and 15 degrees in diameter. Nonaffected fellow eyes served as controls. When macular detachment was present, the MERG showed significantly reduced amplitude and delayed peak latency in a-wave, b-wave and oscillatory potentials (OPs) in all stimulus spots. The reduction of amplitude in 5 degree and 10 degree spots was more significant in b-wave and OPs than in a-wave. In the convalescent stage, the a-wave and b-wave recovered to nearly normal levels, however OPs showed selective delay of recovery. These abnormalities shown by MERG strongly suggest that CSC may involve functional disturbances in the inner retinal layer as well as photoreceptors. It has been assumed that the pathogenic properties of CSC are receptor disorientation and a disturbance in the rate of photopigment regeneration. The present study showed that the abnormal pattern of MERG in CSC cannot be explained simply by the assumption of receptor disorientation or a disturbance of photopigment regeneration by analyzing similar conditions in normal eyes.

Adult↗
PubMed1989

Bull's-eye maculopathy and negative electroretinogram.

The authors studied four patients with a bull's-eye maculopathy and otherwise normal fundus. A single-flash electroretinogram (ERG) with an intense white light stimulus in the dark showed a normal a-wave but reduced b-wave amplitude (negative ERG). Other findings common to all four patients were initially normal visual acuity, subsequent progressive decrease in visual acuity, mild to moderate deficiency of color vision, normal peripheral visual field, relatively well preserved cone ERG, normal 30-Hz flicker ERG, normal EOG, near emmetropia and selective involvement in males. Cone dystrophy, retinitis pigmentosa, congenital retinoschisis, congenital stationary night blindness, and Batten's disease were excluded. The correlation between this disease and benign concentric annular macular dystrophy is discussed.

Adult↗
PubMed1989

Asymmetry of focal ERG in human macular region.

Electroretinograms (ERGs) were elicited by hemicircular (half-disc) stimuli to the upper, lower, temporal and nasal maculas of 26 normal subjects, and the amplitudes and implicit times of the ERGs from opposing macular regions were compared. The amplitudes of a-wave, b-wave and oscillatory potentials (OPs) were significantly larger in the upper macular region than in the lower macular region (P less than 0.05). The amplitudes of a- and b-waves did not differ significantly between temporal and nasal macular regions, but OPs showed enormous asymmetry, with significantly larger amplitudes in the temporal retina than in the nasal retina (P less than 0.001). The implicit times of a-waves, b-waves and OPs did not differ significantly between upper and lower retina, or between temporal and nasal retina. These findings aided analysis of the ERG of a patient with a retinal defect.

Adolescent↗
PubMed1988

Local macular electroretinographic responses in idiopathic central serous chorioretinopathy.

Using focal stimuli to human macular regions, we recorded electroretinograms in 24 patients with central serous chorioretinopathy of recent onset (mean visual acuity, 20/20). The stimulus spot was 10 degrees in diameter. Intact fellow eyes served as controls. The local macular electroretinograms of the affected eyes were significantly reduced and the implicit time in each component was significantly prolonged. The mean (+/- S.D.) amplitudes, expressed as percentages of mean amplitudes recorded in fellow eyes, were 64.6% +/- 22.7% (a-wave), 49.6% +/- 21.0% (b-wave), and 15.0% +/- 21.6% (oscillatory potentials). Two to five months after the macular detachment resolved, recordings in 18 patients showed remarkable recovery of a- and b-waves and shortened implicit times. However, the oscillatory potentials showed significantly small recovery in amplitude. Since oscillatory potentials and b-waves were significantly more deteriorated than a-waves in the presence of macular detachment, and oscillatory potentials showed selective delay of recovery in the convalescent stage, central serous chorioretinopathy may involve functional disturbances in the inner retinal layer as well as the photoreceptors.

Adult↗
PubMed1988

Oscillatory potentials in electroretinograms of the human macular region.

Using focal stimuli, we successfully recorded oscillatory potentials (OPs) in electroretinograms of the macular regions of 72 normal volunteers. The OPs consisted of three to four wavelets with a mean peak interval of approximately 6.5 msec, consistent with that recorded with conventional full-field stimuli over the entire retina. The changes of amplitude in response to the spot sizes and ring stimuli suggested that the distribution of OPs is different from that in a- and b-waves in human macular region.

Action Potentials↗
PubMed1987

Characteristic ERG-flicker anomaly in incomplete congenital stationary night blindness.

Ten patients with the incomplete type of congenital stationary night blindness (CSNB) were examined with a 30 Hz flicker electroretinogram (ERG). After 30 min of dark adaptation, 30 Hz flicker ERG was recorded continuously for 12-15 min under white background illumination. All patients showed an exaggerated increase of amplitude and a universal characteristic change of wave shape as the light adaptation progressed. Thirty normal subjects also showed increased amplitude during light adaptation, but the increase in amplitude was significantly less than in incomplete-type CSNB, and there was little change in wave shape. The same procedure was applied to patients with complete-type CSNB, retinitis pigmentosa, congenital retinoschisis, cone dystrophy, and Oguchi's disease; neither the exaggerated increase of amplitude nor the wave change was seen. Our results indicate that incomplete-type CSNB is a newly identified cone-rod dysfunction syndrome with a special functional property.

Electroretinography↗