Abstract
Abstract: :
Purpose Flash–VEP represents a method commonly used to evaluate the visual function when pattern VEP cannot be recorded due to opaque media, low visual acuity, instable fixation of various reasons and reduced compliance in children, mentally disabled and patients with malingering. We wanted to evaluate the use of a new stimulator provided for flash VEP in normals as well as patients with optic nerve disorders. Methods 40 eyes of 20 healthy volunteers with a visual acuity of 1.0 or higher were stimulated unilaterally and bilaterally using the standard ISCEV–recommended electrode setup with the RETIscan LED goggles and a Toennies Multiliner system. 100 averages were sampled per recording at a 8000mcds/m2 red stimulus intensity during 5 minutes recording time with 5Hz/5ms. Analysis included N75, P100 and N140 latencies as well as the P100 amplitudes. Results In normal eyes, binocular implicit times for the P100 amplitudes varied from 92.4 to 195ms (median 149ms) while P100 implicit times varied from 88ms to 195ms (median 159ms). The median difference between right and left intra–individual recordings were 23.4 to 0.6ms (median 4.2ms) for P100 implicit times. P100 amplitudes ranged from 4.2 to 20.2 µV (mdedian 10.3V). In the patients with traumatic or degenerative optic nerve affections we found significant uni– or bilateral increase in P100 implicit times or total loss. Pupil dilation or closed eyes did not affect the results in healthy volunteers. Conclusion Although there is a wide variability of normal results, the new stimulation system appears to be sufficient for easy F–VEP stimulation under conditions where pattern–VEP stimulation is not appropriate, especially in mentally disabled and infants where positioning in front of a strobe–light stimulator may not be appropriate.
Keywords: clinical (human) or epidemiologic studies: systems/equipment/techniques • neuro–ophthalmology: optic nerve • visual cortex