Objective To investigate the distribution properties of multifocal pattern visual evoked potential across visual field. Methods Multifocal pattern visual evoked potentials(VEP) of 14 normals were measured with VERIS Science TM 4.0. The visual stimuli were dart board 60 with patterns which consisted of 60 patches arranged in dart board configuration spanning a 26? visual field. The temporal modulation of each patch was controlled by a special type of pseudorandom sequence called binary m-sequence. The electrodes were placed at equal distances 2 cm inferior to and 2 cm superior to and straddling the inion . The first slice of the second order kernel for each stimulus patch was analysed. The 60 patches were grouped into several sectors. The summed responses of these sectors were analysed and compared. Results Compared with that of the lower hemifield, the polarity of the multifocal VEP of the upper hemifield was reverse, and the latency delayed, the response density decreased. With the eccentricity increased, the response density of the multifocal VEP decreased. The properties of the multifocal VEP of the horizontal sectors were different from that of the vertical sectors. Conclusion VEP of many locations within visual field could be recorded simultaneously in a short time with the method of mutifocal VEP. The multifocal VEP showed different properties in different sectors within visual field.

ObjectiveTo analyze the symmetry of multifocal visual evoked potential (mfVEP) between both eyes in normal subjects. Methods The monocular mfVEP of both eyes in thirty-six normal subjects (72 eyes) was tested with VERIS Science 4.0. The stimulus was the pattern reversal dart array consisted of 60 sectors each included 16 black-white reverse patterns. The visual stimulation was controlled by the binary pseudo-random m-sequences and subtended approximately 25 degrees. Results There existed no statistically significant difference of P1 latencies and amplitudes between correspondent quadrant visual field of both eyes. The data difference of the ipsilateral quadrant visual fields was greater than those of the correspondent quadrant visual field. The comparison among four quadrant visual fields in right eye or left eye each showed that there was statistically significant difference of P1 latencies between the superionasal quadrant visual field and inferiotemporal or inferionasal quadrant visual fields. Conclusions The symmetry of normal mfVEP is more dominant in retina than that in visual cortex.

Objective To investigate the characteristics of multifocal visual evoked potential (mf-VEP) in healthy individuals, and provide normal reference values for its clinical application. Methods The mf-VEP of 37 healthy individuals (70 eyes) were examined by VERIS Science TM 4.0. The visual stimulus was a dart board with patterns consisted of 60 patches spanning a 25? visual field. The length of m-sequence was 2 14-1. The results were recorded by bipolar occipital straddle. The signal was amplified 100 K and was put through a band-pass filter between 3 and 100 Hz. The first slice of the second order kernel was analyzed by VERIS software. The summed responses of fields with different stimulus were analyzed and compared according to different ages, genders and eyes. Results The latencies and response densities of amplitude had statistically significant differences both in dimidiate and quartered field(P 0.05). Conclusions The mf-VEP of healthy individuals can reflect the VEP at different field locations objectively with its specific physiological characteristics, which may provide normal reference values for its clinical application.

Objective To investigate the influence of experimental scotoma on multifocal visual evoked potential (mf-VEP). Methods The mf-VEP of 10 healthy individuals (20 eyes) was measured with VERIS Science 4.0. Every eye was measured for 3 times. The right eye was measured with full field stimulation and upper hemi-field or lower hemi-field masked. The left eye was measured with full field stimulation and central three-rings area or lower nasal field masked. The first slice responses of the second order in different field were analyzed and compared by VERIS software. Results The mf-VEP in masked area was undetectable or obviously decreased in all subjects. In most unmasked field, the amplitudes of mf-VEP were not changed, except that in some place decreased slightly with statistically significant difference in comparison to the full field stimulation mode. Conclusion mf-VEP is influenced with experimental scotoma. The mf-VEP changes are consistent with the visual field masked.

Background Behcet's disease is a refractory panuveitis with high blindness rate.Multifocal electroretinography (mfERG) is a useful tool for the evaluation of the function of the posterior retina.ObjectiveThe aim of this study is to assess the characteristics of Behcet's disease using the mfERG.Methods mfERG was recorded in 68 eyes of 39 cases with active stage of Behcet's disease.All of the patients were diagnosed based on the Standard of International Study Group for Behcet's Disease and assigned to the cystoid macular edema (CME) group and the diffuse macular edema (DME) group after assessment by fundus fluorescein angiography (FFA).Seventeen normal subjects were used as controls.Oral informed consent was obtained from all of the subjects prior to this trial.mfERG recording followed the ISCEV Guidelines for Clinical Multifocal Electroretinography (2007 edition).The response density and latency of P1 and N1 waves in 6 rings were analyzed and compared.Results The amplitudes of N_1 waves from rings 1 through 6 and N1 wave from rings 1 through 5 were significantly declined in patients with Behcet's disease compared with normal control (P＜0.01).All of the latencies of P_1 waves from rings 1 through 6 were insignificantly shortened in patients with Behcet's disease compared with normal control (P＞0.05).The amplitudes of P_1 and N_1 waves from rings 1 through 6 in diffuse macular edema group were considerably lower than those in the cystoid macular edema group (P＜0.05,P＜0.01).A test of visual acuity showed a negative correlation to the amplitude and latency of N_1 wave (r=-0.36,-0.37,P＜0.05 ) and a positive correlation with the amplitude of N1 wave (r=0.43,P＜0.05) in the DME group.In the CME group,a test of visual acuity presented a negative correlation to the amplitude and latency of N1 wave and latency of P1 (r=-0.41,-0.35,-0.40,P＜0.05 ) and a positive correlation with the amplitude of P1 wave (r=0.48,P＜0.05).Conclusion mfEGR demonstrates that retinal electro-activity is abnormal in eyes with Behcet's disease.The distinct functional disorder is situated around the fovea.

OBJECTIVETo study the effect of radiotherapy of nasopharyngeal carcinoma on visual evoked potential (VEP).

METHODSVEP of 63 patients with nasopharyngeal carcinoma were tested before, at the end of, half a year, one year, 2 years and 3 years after their radiotherapy.

RESULTSWithin the male group, one year after radiotherapy, the latency of VEP was significantly delayed than that before and at the end of radiotherapy, while the amplitude was decreased significantly. Two years after radiotherapy, the latency of VEP was significantly delayed more than that before radiotherapy. However there was no significant difference among VEP at the end of, half a year and 3 years after radiotherapy. Within the female group, 2 years after radiotherapy, the latency of VEP was significantly delayed than that before radiotherapy. Three years after radiotherapy, the latency of VEP was significantly delayed than that before, at the end of, half a year and one year after radiotherapy. There was no significant difference in VEP amplitudes before and after radiotherapy.

CONCLUSIONWithin the male group, the abnormal delay of VEP latency mostly happens one or two years after radiotherapy. Within the female group, the significant delay of VEP latency happens at the end of radiotherapy and lasts for 3 years, while the VEP amplitude does not change significantly during the 3 years after radiotherapy. The result indicates that the sustained radiation damage within the female visual nerve system starts at the end of radiotherapy, but to a lesser degree. It was shown that radiotherapy of nasopharyngeal carcinoma certainly damages the visual nerve system, though there is sex difference in the impairment.

Adult ; Evoked Potentials, Visual ; radiation effects ; Female ; Humans ; Male ; Middle Aged ; Nasopharyngeal Neoplasms ; radiotherapy ; Sex Factors ; Time Factors