Inter-hospital comparison of Ganzfeld ERG photostimulators.
The periodic calibration and control of electroretinographic (ERG) stimulators is often neglected due to the difficulties in accurate measurements of the stimuli. Comparison of measurements carried out in different laboratories has been very difficult, as the accurate parameters of the stimuli used usually are not known. In some cases it is assumed that if the stimulator type is known, comparisons can be carried out. We have tested the Ganzfeld flash stimulators used in the departments of clinical neurophysiology of 3 major hospitals in Finland, namely Kuopio University Hospital, Turku Central University Hospital, and Tampere University Hospital, Measurements, performed with a new type of photometer, show that the intensities varied by 42% between the highest and lowest intensity stimulators at nominally identical settings. The measurements underline the findings that identical stimulators will not necessarily produce identical stimuli. These observations also indicate that the stability of the stimuli can be improved by the proper choice of stimulator output settings.
Mäkelä
K
K
Tampere University Hospital, Dept. of Clinical Neurophysiology, Finland.
Hölttä
V
V
Jääskeläinen
S
S
Könönen
M
M
Jousmäki
V
V
D004596:Electroretinography / Q000295:instrumentation*; D006801:Humans; D010775:Photic Stimulation; D012160:Retina / Q000502:physiology