Author: Giulia Righetti (Germany)
Co-authors: Susanne Kohl, Melanie Kempf, Katarina Stingl, Krunoslav Stingl
Purpose
Achromatopsia (ACHM) is a rare autosomal recessive inherited disease with an incidence of 1 in 30,000 characterized by cone dysfunction. Routine clinical diagnostics is based on full-field electroretinography (ERG) showing a lack of cone responses following photopic stimuli. Rod responses in individuals with ACHM are normal, or nearly normal, after dark adaptation with flashes in scotopic recordings. The retinal processes recorded by full-field ERG following a flash stimulus can be described by distinct components (a-wave, b-wave, and oscillatory potentials). Many pieces of evidence suggest that a- and b-waves reflect the activity of the photoreceptors and the ON-bipolar cells respectively, while Oscillatory Potentials (OPs), are described as components that appear between the a-wave and the ascending b-wave activation and are considered to be generated by the inner retinal layer cells. The present study aims to characterize the process of the OPs in the temporal and frequency domain in individuals affected by ACHM, exploring how the absence of cone responses compared to healthy subjects affects OPs.
Setting/Venue
1. University Eye Hospital, Center for Ophthalmology, University of Tuebingen, 72076 Tuebingen, Germany; 2. Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tuebingen, 72076 Tuebingen, Germany; 3. Center for Rare Diseases, University of Tuebingen, 72076 Tübingen, Germany
Methods
The analyses were performed on scotopic full-field ERG recordings according to the standards (10 scotopic cd·s·m−2) obtained from 63 healthy participants (42 females; mean age 39.6 ± 16.7 SD) and 41 individuals with genetically confirmed ACHM (20 females; mean age 30.9 ± 14.1 SD). The stimulation at this luminance intensity is chosen since it represents a mixed rod-cone response in healthy subjects and a good model for exploring the effect of absent cone activity in ACHM for the generation of OPs. A continuous complex Morlet wavelet transform has been performed on the ERG signal in the range of 0.1-300 Hz to characterize the dynamics of the OPs of both groups. Time-frequency maps were created for each subject and compared between groups using a cluster-based permutation test in order to identify significant differences.
Results
The cluster-based permutation test reveals a significant cluster (p <0.05) on the comparison between healthy subjects and patients with ACHM at the time and frequency range of the OPs. These results show that OPs are strongly reduced or totally absent in achromats even if they have fully functional rods.
Conlusions
The continuous wavelet transform appears to be a useful method for analyzing the dynamics of the ERG components and characterizing the OPs. The analyses of ERG data from individuals with achromatopsia help to better understand the retinal processes in the absence of cone function. The result suggests that cones play an essential role in the raising of the OPs.
Financial Disclosure
None
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