98th Annual Meeting DOG 2000

V 168

High-resolution functional retinal topography by element-wise analysis of multifocal ERG data

M. W. Seeliger

Purpose: Multifocal electroretinography (MF-ERG), a diagnostic method that allows to determine the topographical distribution of retinal dysfunction, has clinically and scientifically become more important in recent years. However, the current analysis procedures involve a reduction of data that either reduces the topographical resolution to speed up manual evaluation or joins amplitude and implicit time information. The goal of this work was thus to develop an analysis method that does not reduce spatial resolution.

Methods: Datasets exported from the two systems available (RetiScan, Roland Consult and VERIS, EDI/Haag-Streit) were processed on a PC. For the automated evaluation of the transient ERG signals (1st order kernel), a template was shifted point by point and multiplied with the local signal under investigation. This yields the scalar product as a function of the shift. The maximum of this function indicates the best match obtainable and provides a measure of local amplitude, whereas the amount of shifts necessary to reach the maximum is a measure of implicit time. The amplitude difference between the maximum and the second highest peak of this function furthermore allows to evaluate the quality of a local signal and is associated with diagnostic confidence.

Results: The application of this method in exemplary diseases like Stargardt┬ĺs disease (central loss of amplitude, scarcely changed implicit times) and the retinitis pigmentosa group (peripheral loss of amplitude, prolonged implicit times) yielded robust results and was far less influenced by noise than the manual analysis by cursor placement.

Discussion: The proposed method appears to be a valuable addition to the current techniques of MF-ERG data analysis. It is important to mention that both local amplitude and implicit time information is provided. The robustness allowed to obtain satisfactory results even in regions with markedly reduced signal quality.

Retinal electrodiagnostics research group, Department of Ophthalmology, University of Tuebingen, Schleichstra├če 12-16, D-72076 Tuebingen