Effects of ethyl alcohol on the directly recorded standing potential of the human eye.

The effects of ethanol on the human standing potential (SP) were studied with a recently developed method, which allows direct SP recordings by means of a suction contact lens, temperature stabilized calomel electrodes and d.c. amplification. It is well known that the human SP oscillates with a frequency of about 2/hour in response to a sudden change in illumination. In the present paper marked cyclic variations of the SP, resembling damped oscillations, were provoked by a small oral dose of ethyl alcohol. A first maximum was reached after about 10 min. The difference in amplitude between the peak and the trough of the first oscillation was of the order of 4 mV. The oscillatory frequency was about 2/hour. The length of a cycle varied between 25 and 34 min in different volunteers, being fairly constant in the same subject on different occasions. The SP response to ethanol was similar both under scotopic and photopic conditions. The results correlate well with earlier findings of 2/hour oscillations in c-wave amplitude in response to ethanol, as may be expected considering the partly common origin of the c-wave and the SP.     

ERG and EOG in progressive paravenous retinochoroidal atrophy

A case of paravenous retinochoroidal atrophy was followed over a period of more than 2 years. Rapid progression of the disease was reflected in the deterioration of visual acuity and fields. Electroretinographic recordings revealed reduced photopic and scotopic amplitudes according to the extent of the retinal lesions. In electro-oculography virtually no slow and no fast light-induced oscillations could be recorded. These results suggest an involvement of the entire retinal pigment epithelium.     

Congenital achromatopsia: electroretinogram in early diagnosis

PURPOSE: Achromatopsia is a hereditary disease responsible for congenital low vision. Patients present with nystagmus, abnormal visual behavior or photophobia. Only the electroretinogram (ERG) can confirm the diagnosis in infants. PATIENTS AND METHODS: Thirty children referred for nystagmus or low vision were included in this retrospective study. A complete ophthalmological examination, an ERG and when possible a color vision test (Ishihara, Farnsworth 15 Hue test) was done. A Ganzfeld ERG was performed in accordance with ISCEV standards in patients more than 6 years of age. In younger patients, a simplified method using electroluminescent diode stimulation was used and a comparative ERG in accordance with ISCEV standards was performed when the patients were old enough. RESULTS: The ERG response was identical in children and adults. It confirmed the diagnosis of achromatopsia: the scotopic components obtained in dark adapted conditions were normal, (scotopic a-wave, b2 wave). The photopic components, recorded in light-adapted conditions, in order to inhibit the scotopic response (photopic wave, b1 wave), were not recordable. The color vision tests confirmed color blindness; however, in some patients color denomination was correct. CONCLUSION: The simplified ERG procedures performed in our series were reliable in detecting achromatopsia. However, it may not be sufficient to discriminate complete from incomplete achromatopsia.     

Three-dimensional analysis of averaged electro-retinograms: normal appearance and bioelectric artifacts

In 10 normal subjects, three-dimensional analysis (X-Y plane and time) was carried out of the dominantly photopic and scotopic components of the electroretinograms (ERG) for the purpose of functional imaging of the retina, after having evaluated bioelectric artifacts. The study of the artifacts had revealed that the major causes of distorting the topographical distribution were blinking, myogenic activities, eye movement, eye position and background activities of the electroencephalograms. In normal subjects, the maximal amplitude of the dominantly scotopic components was located around the lower eyelid, while that of the dominantly photopic components was situated around the upper eyelid. The mechanisms of the equivalent dipole axis of the dominantly photopic and scotopic components were different. However, similar changes in the equivalent dipole axes were found during the periods of eccentric eye positions. Similar topographical characteristics were noted in the latency mapping. The isopotential line of the dominantly scotopic components had a steep gradient and were suggestive of a superficial (peripheral retinal) origin, while that of the dominantly photopic components had a gradual gradient and seemed to be of deep (central retinal) origin. ERG topography would make functional imaging of the retina possible and would be of great diagnostic value.     

Stimulus alternation and the purkinje shift

Simultaneous spectral sensitivity determinations of the human electroretinogram and the visual evoked potential were made over an adaptation range extending from scotopic to photopic. Determinations were made for the amplitude of the B wave and the late negative potential of the electroretinogram and for the latency of a conspicuous peak of the VEP.³ Alternating stimuli were delivered to a peripheral region of the visual field. Responses at both recording sites matched the scotopic CIE luminosity function at low levels; at high levels they matched Wald's curve for the peripheral cones. The transition from scotopic to photopic function with light adaptation was not abrupt. Mixed activity was the rule over most of the range of adaptation, but the relative prominence of photopic activity increased with light adaptation. The spectral sensitivities of the responses from the two recording sites were similar but not identical with the electroretinogram receiving a stronger contribution from the scotopic system over much of the adaptation range.     

Achromatopsia with amblyopia

39 patients suffering from congenital achromatopsia were investigated by various methods, including electroretinography, during both light and dark adaptation. This condition was typically expressed by the presence of photophobia, low visual acuity, nystagmus and various degrees of ametropia. The fundus was normal in 9 cases. Most of the other cases showed various macular or foveal abnormalities. 24 patients showed complete absence of color vision, and practically all displayed the ‘scotopic line’ in the Farnsworth Panel D-15 test.

The electroretinogram (ERG) was almost always extinct in light. In the dark, in most patients the ERG displayed the scotopic mechanism solely, but some ERGs indicated subnormal photopic components either at the beginning or during all dark adaptation. This presence of photopic activity in the ERG of achromats was verified by 2 additional experiments. In one, the recovery of the positive wave of four achromats was compared on a percentage scale with that of four normal subjects and found to be similar, although the slightly faster course in achromats indicates less photopic activity than in normals. In the second, the positive amplitudes of the ERGs of 12 achromats with purely scotopic ERGs were recorded at completed dark adaptation as function of increasing stimulus intensities, all above the photopic threshold, and compared with those of 16 normal subjects. The amplitudes increased linearly with the 1.2 log intensity range in both groups, though the slope of the curve of the achromats was 1/4 that of the normals. In another experiment, the positive wave of the ERG, as elicited by light over 5 log units in the scotopic range, was found in an achromat to be of very similar shape as that of a normal, indicating scotopic acitivity to be similar in both subjects.

The fact that, nevertheless, photopic components were not demonstrable in most ERGs, despite present photopic activity, can be explained by the relatively insensitive electrical method coupled with the subnormality of the retinal photopic mechanism in every achromat.

     

Scotopic versus photopic pattern onset-offset electroretinograms

We investigated the contribution of rods and cones to the human pattern electroretinogram to onset and offset checkerboards of different spatial frequency and wavelength in a 39° × 39° field. Under strictly scotopic conditions, there was a negative potential at onset and a positive potential at offset, whereas under photopic conditions, there was a positive potential at onset and a negative/positive potential at offset. Thus, the waveform to pattern onset (offset) was that of the luminance electroretinogram to decreasing (increasing) luminances. For pattern onset, the sensitivity difference 486–601 nm under scotopic and photopic conditions closely followed the luminosity function of rods and cones. The amplitude of the scotopic onset response increased with check size up to 3°30 and that of the photopic onset response, up to 30. With larger checks, the scotopic and photopic onset response markedly decreased. This indicates antagonistic center-surround organization of the receptive fields under both scotopic and photopic conditions. By contrast, the offset response monotonically increased with check size under scotopic and photopic conditions, which suggests a luminance component in the pattern electroretinogram. Consequently, the pattern electroretinogram to reversing checker-boards has to be regarded as a mixture of both pattern- (contrast) and luminance-specific components.     

The spatial organization of retinal receptive fields in light and darkness as revealed by the pattern electroretinogram

The spatial selectivity of the electroretinogram in response to pattern onset-offset stimuli was studied in man at several levels of adaptation ranging from scotopic to photopic levels. Under conditions of rod function the peak of the spatial selectivity based on amplitude measurements of the pattern-onset response occurs at a low spatial frequency. With increasing light adaptation a gradual shift of the selectivity to higher spatial frequencies occurs. This change in the character of the response can be explained by the assumption that antagonistic center-surround retinal receptive fields contribute to the response, which are larger under scotopic than under photopic levels of stimulation.     

不同光照条件下近视患者Kappa角的特征及变化规律

目的 观察预行飞秒激光原位角磨镶术(FS-LASIK)的近视患者在不同光照条件下Kappa角的特征及其变化规律。方法 采用自身前后对照试验。选取2021年6月至8月在江西省人民医院近视矫正中心预行FS-LASIK的近视患者104例(208眼)。用Sirius三维角膜地形图分别测量患者双眼在明视、黄昏视和暗视条件下的瞳孔直径和瞳孔中心偏移量。并将瞳孔中心偏移量在直角坐标系中转换为Kappa角水平分量和Kappa角垂直分量,并分析其变化规律。分析患者双眼瞳孔直径和Kappa角之间的关系。结果 患者右眼Kappa水平分量在明视、黄昏视和暗视条件下分别为(0.00±0.13)mm、(-0.06±0.13)mm、(-0.12±0.13)mm,差异有统计学意义(P<0.05);患者左眼Kappa角水平分量在明视、黄昏视和暗视条件下分别为(-0.04±0.14)mm、(0.02±0.13)mm、(0.08±0.13)mm,差异有统计学意义(P<0.001)。患者双眼瞳孔直径在不同光照条件下差异均有统计学意义(均为P<0.001)。两两比较结果显示,患者双眼瞳孔直径和Kappa角水平...     

Alteration of electroretinographic recordings when performed under sedation or halogenate anesthesia in a pediatric population

Fran The effects of sedation and of halogenate anesthesia on electroretinographic recordings were investigated by reviewing the hospital charts of 27 patients who were eventually diagnosed free of retinal disease. The same ERG protocol was performed in conscious (n=9), sedated (chloral hydrate or pentobarbital sodium, n=9) and anesthetized (halothane or isoflurane, in combination with N2O, n=9) young patients. Sedation decreased the a- and b-wave amplitude of the scotopic bright-flash response, without affecting implicit times. ERG recordings performed in photopic conditions showed minimal disturbances. Anesthesia spared the a-wave of the scotopic bright-flash response but decreased more severely the b-wave. In addition, anesthesia reduced the amplitude and prolonged the implicit time of the photopic responses, affecting predominantly the ionotropic glutamate dependent OFF components (peak of b-wave, 0P4 and 0P5). The normal retinal physiology is affected by sedation and anesthesia through different mechanisms that still remain to be fully elucidated. These alterations in electroretinographic recordings must be considered when evaluating ERGs obtained under similar sedation/anesthetized conditions.