Variability of flashes and background luminances of clinical electroretinography stimuli across 14 UK centres

Abstract

Three different flash strengths (dim, 0.01 cd s m−2; strong, 3 cd s m−2; strongest, 10 or 30 cd s m−2) and one adapting field luminance (30 cd m−2) are used for clinical electroretinograms (ERGs). To quantify their variability for local, LED-flash protocols, and for an ISCEV-specified, xenon-flash protocol, photometric measurements were made at 14 ERG centres across the UK. For local protocols, flashes were within a median of 0.01 log units of nominal, target levels and six, nine, eight and eight of 14 centres were within ISCEV tolerance (±0.05 log units) for dim, strong, strongest flashes and backgrounds, respectively. For the ISCEV-specified protocol, flashes were within a median of 0.02, 0.001 and 0.01 log units of ISCEV target dim, strong and strongest flashes, and fewer (5/12, 7/13, 3/13 and 11/13) centres were within ISCEV tolerance for dim, strong and strongest flashes and backgrounds, respectively. Paired LED–xenon comparison for a subset of centres showed close agreement. Variability of flashes was less for LED than xenon flashtube sources for strong and strongest flashes; for the strongest flash, LED flashes were closer to target values than xenon flashes. These data support a recommendation of LED use for clinical electroretinography.