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A significant difference in the response density of the MF-ERG response has been suggested for every 2 diopter change of refraction. The influence of refractive blur on the MF-ERG was studied in 8 healthy volunteers using either the VERISTM system (Group A: n=5) or Retiscan(TM) (Group B: n=3). For each eye recordings were obtained with a corrective lens of -3 dpt, 0 dpt, +3 dpt and +6 dpt placed in front of the contact lens electrode. The viewing distance was adjusted to compensate for the induced changes in the retinal image size. When the changes in retinal image size due to the refractive lens were compensated for, no influence due to refraction was observed in either latencies or amplitudes of (KI (P > 0.05). This held true for the central response average (four degrees) as well as for the outer 6-25 degrees. In KII.1 only the peripheral amplitudes of Group B showed an influence due to refraction (P < or = 0.05). This may be due to adaptation as the recordings of group B were obtained in succession. As expected, significant differences were observed when the recordings obtained with the different systems were compared (P < or = 0.05).

319 patients with a solar retinopathy were seen in an eye clinic in Nepal within 20 months. All patients had either a positive history of sun-gazing or typical circumscribed scars in the foveal area. In more than 80% of the patients the visual acuity was 6/12 or better and did not deteriorate over time. 126 (40%) patients had a history of gazing at the sun during an eclipse, 33 (10%) were sun worshipers and 4 (1%) were in both categories. Three years later 29 patients were re-examined in a follow-up study. Only 16 had had visual disturbances directly after they had gazed into the sun. No colour vision defects were seen in any of the 44 affected eyes, when tested with Panel D 15, while four patients (6 eyes) had some uncertainty with the tritan plates of the Ishihara test charts. Metamorphopsia were recorded in 11 eyes. Five German patients with solar retinopathy were examined in more detail. Colour contrast sensitivity (CCS) was tested for the central and the peripheral visual field. CCS for tritan axis was raised in all patients for the central visual field, while it was normal for the peripheral visual field.

The spatial response function of the electroretinogram (ERG) to contrast checkerboard pattern reversal at several check sizes was determined at a fixed contrast. The influence of the rate of modulation on the spatial response function was assessed. Reversing square wave patterns were presented at eight temporal frequencies ranging from 1 to 25 reversals per sec. The waveform consisted of an initial positive and a subsequent negative deflection. Irrespective of the temporal frequency, the spatial response function of the positive component did not show a spatial tuning. The amplitude of the negative component exhibited a pronounced attenuation of the response at check sizes larger than optimal. Mean maximal amplitude was found at an optimal check size between 25 and 50 min of arc. A distinction between a positive or negative component was not made for temporal frequencies higher than 10 reversals per sec, since the waveform at these modulation rates consisted merely of a sinusoidal steady-state response. The spatial response function obtained at 14 reversals per sec, resembling that of the negative component, exhibited a prominent spatial tuning. The results demonstrate that the pattern ERG has at least two components: a positive component which is not specific to changes in retinal distribution of contrast, followed by a negative wave showing spatial tuning across temporal frequency.

The major goal of this investigation was to describe and characterize response components of graded retinal responses in man and cat as a function of check size of the spatial stimulus. The arterially perfused cat eye enabled us to record the pattern reversal electroretinogram (PERG) and simultaneously summed activity of retinal ganglion cells by recording a compound action potential of the optic nerve (ONR). Checkerboard pattern reversal stimuli were presented at a low temporal frequency (recording 2 reversals in each trace), while a number of parameters such as check size, modulation depth and field size have been varied in order to elucidate similarities in response characteristics between the PERG and ONR. The striking similarity area dependence of the PERG and ONR points to ganglion cell activity as well as summation within the latter's receptive field center, reflected in the PERG. A fractionation was obtained of the PERG into two separate components generated by specific changes in spatial contrast and by luminance, respectively. The spatial response component of the PERG recorded in man from the enucleated cat eye closely resembled and consisted of a negative deflection. This component is preceded by a positive deflection sensitive to luminance changes and prominent upon peripheral retinal stimulation. It is anticipated that mild to moderate abnormalities of the ganglion cell activity will be first reflected in the negative contrast component upon central retinal stimulation.

Eighteen patients with acute retrobulbar neuritis were examined by visual field analysis and electroophthalmological recordings. The visual fields were measured to 30 degrees with the automatic perimeter Octopus 201. The pattern-evoked cortical potential showed an increased P-100 latency followed by a decrease in 12 patients during the first two weeks of the disease. This latency change cannot be explained by remyelinization. Teh positive component of the pattern ERG (P-50) was reduced in all acutely affected eyes in comparison with the fellow eye. During recovery, the amplitude of the positive PERG component increased to normal, but remained slightly reduced in comparison with the response from the fellow eyes. Thirteen patients out of 18 were clinically and electrophysiologically diagnosed as having unilateral retrobulbar neuritis. However, static perimetry showed paracentral scotomas in the fellow eye in 5 cases. Recovery of the severely affected eye was accompanied by complete normalization of the visual field in the fellow eye. Thus static perimetry seems to be a more sensitive test than even the visual evoked potentials for detecting lesions in the visual pathway.