Abstract
Purpose::
Aim of this study was to explore the effect of different wavelengths and intensities of stimulus and background illumination on amplitudes and implicit times of a-wave, b-wave and photopic negative response in normal subjects
Methods::
In 14 eyes (dilated pupils with Tropicamide) of 14 healthy subjects (age: 41.5 ± 8.6 years) flash (3 ms) photopic electroretinograms were recorded using a full-field LED stimulator (Q450, Retiport, Roland Consult). ERGs elicited by different colors (peak wavelength of 458, 470, 591, 625 nm and white) and increasing photopic luminances (0.03 to 3 cds/m²) were tested on blue (458, 470nm), orange (591nm) and white backgrounds (4 luminances each: 10, 25, 50 and 100 cd/m2). Recordings were performed with Jet contact lens electrodes after 2 min of adaptation.
Results::
All waves’ amplitudes increased with increasing stimulus intensity and decreasing background luminance. Using the present photopically matched stimulus conditions, the highest amplitudes of the a-wave, b-wave and photopic negative response were found for blue stimuli on all backgrounds. The amplitude of the photopic negative response did not show any significant differences for orange, red and white stimuli. Implicit times of a and b waves decreased with increasing stimulus intensity and background luminance. The dependency of the b wave latency on stimulus intensity was, however, not monotonous: at high stimulus intensities, latency increased with increasing stimulus strength.
Conclusions::
The response of the present blue flash-electroretinogram show potential to be an adequate method in exploring blue cone mediated retinal function. An equation of the stimuli and backgrounds for rod excitation should be considered. The behaviour of the b wave latency indicates the presence of multiple mechanisms.
Keywords: retina • electroretinography: clinical • photoreceptors