[Multifocal ERG with confocal scanning laser ophthalmoscope. Comparison with monitor simulation]

The clinical applications of multifocal electroretinography: a systematic review

Multifocal electroretinography (mfERG) is an investigation that can simultaneously measure multiple electroretinographic responses at different retinal locations by cross-correlation techniques. mfERG therefore allows topographic mapping of retinal function in the central 40-50 degrees of the retina. The strength of mfERG lies in its ability to provide objective assessment of the central retinal function at different retinal areas within a short duration of time. Since the introduction of mfERG in 1992, mfERG has been applied in a large variety of clinical settings. This article reviews the clinical applications of mfERG based on the currently available evidence. mfERG has been found to be useful in the assessment of localized retinal dysfunction caused by various acquired or hereditary retinal disorders. The use of mfERG also enabled clinicians to objectively monitor the treatment outcomes as the changes in visual functions might not be reflected by subjective methods of assessment. By changing the stimulus, recording, and analysis parameters, investigation of specific retinal electrophysiological components can be performed topographically. Further developments and consolidations of these parameters will likely broaden the use of mfERG in the clinical setting.

Multifocal ERG recording with simultaneous fundus monitoring using a confocal scanning laser ophthalmoscope

PURPOSE

To assess the general feasibility of recording multifocal electroretinograms (mfERGs) with simultaneous fundus monitoring in a clinical setting.

METHODS

An mfERG system (RETIscan) and a confocal scanning laser ophthalmoscope (Heidelberg Retina Angiograph) were connected to record mfERGs elicited by a pseudorandom binary m-sequence stimulus generated by a 514 nm laser source. Recordings were compared to a conventional mfERG system using monitor stimulation. A total of five subjects (two normal subjects and three patients) were examined.

RESULTS

In normal volunteers records obtained by the fundus-monitored mfERG showed highest response densities in the central fundus area and a decrease of response amplitudes towards the periphery paralleling cone receptor density. However, compared to the monitor stimulation, the drop-off of amplitudes as a function of eccentricity was not as clearly defined. The responses obtained from patients with retinal diseases were diminished in the areas of retinal dysfunction.

CONCLUSIONS

These preliminary findings indicate that the technique of laser stimulation in principle allows for topographic retinal recording. This method might be useful, for example if the retinal position of the stimulus array is not centred onto the fovea but deviates due to fixation problems. However, further improvement of the technique appears necessary before considering routine clinical application.