Purchase this article with an account.
M. E. Pennesi, R. G. Weleber; Slow Insensitive Scotopic Responses in Three Children With Leber Congenital Amaurosis (LCA): A New Electroretinogram (ERG) Phenotype?. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5317.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
To describe a new ERG phenotype seen in association with LCA.
Full field ERGs were performed using intravenous propofol sedation on three patients during workups for congenital nystagmus. Initial testing ranged from 4 months to 2.5 years. ERGs were recorded with Burian-Allen contact lens electrodes and a Ganzfeld stimulator that presented intensities over a range of -3.1 to +0.6 log cd-s/m2. Dark- and light-adaptation times were 45 and 12 minutes. Scotopically matched blue and red stimuli tested dark-adapted rods and cones. 30 Hz flicker was presented with and without a 10-cd/m2 background.
All three patients presented with clinic findings of LCA including severely decreased vision, nystagmus, and poorly responsive pupils. The two youngest patients had normal fundus exams. The oldest patient demonstrated vascular attenuation and granular RPE mottling. All three patients had identical responses on the full field ERG. No discernible responses were seen scotopically using dim flashes of white light (-3.1 to -1.8 cd-s/m2) or blue light. At higher intensities under scotopic conditions (-0.6 to 0.6 cd-s/m2) a slow, delayed waveform emerged. The average onset latency of this response was 50-80 ms and the time to peak was 145-190 msec. The amplitude of the wave grew and the time of onset decreased with increasing intensity. The amplitude at the highest intensity tested was 50-100 microvolts. No discernible cone responses were seen to single flash or to 30 Hz flicker. We have termed this unusual ERG phenotype Slow Insensitive Scotopic Response. Interestingly, repeat ERG measurements on one of these patients three years later at age six demonstrated a notable decrease of this slow scotopic response.
The source of the Slow Insensitive Scotopic Responses seen in these patients is unclear. A specific defect of photoreceptor sensitivity and responsiveness could underlie the findings. These signals could also result from inner retinal rewiring or redirection of signal responses due to massive photoreceptor death. Another possibility is that this signal could arise from melanopsin-containing ganglion cells. The source of these signals will be further explored.
This PDF is available to Subscribers Only