Purchase this article with an account.
T. Wright, C. Westall; Techniques for Testing Infants and Young Children Using the MfERG. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5975.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Key to successful multifocal electroretinogram (mfERG) testing is accurate and consistent positioning of the stimuli on the retina. In awake subjects it is widely recognized that fixation should be steady and it is usually possible for subjects to comply voluntarily with this requirement. In an infant population full field and multifocal electroretinogram testing fixation stability is more problematic due to the subjects’ inability to comply.We have been performing full field electroretinography successfully on infants under 5 years (weight dependant) using sedation. Modifications to our standard mfERG testing protocol allow us to extend this technique so that mfERG recordings can be obtained.
Children receiving vigabatrin therapy for infantile spasms undergo ffERG’s under sedation as part of our clinical protocol. Informed consent was obtained from the parent/guardians according to the guidelines of the Helsinki declaration. A short mfERG recording protocol using a 61 hexagon unscaled stimulus (M-sequence exponent 13) and Burian-Allen electrodes was performed.Preliminary studies indicated that eye position was the biggest problem with infant mfERG testing. Good eye position was obtained using an infrared fundus imaging system. The use of an unscaled stimulus allows accurate location of the fovea after recording. The hexagon map can then be transformed in order to align recordings for comparison. Eye position was maintained best when sedation was at its heaviest i.e. immediately after application.To estimate the reliability of this method, subjects were tested twice in the same recording session with the stimulus being repositioned between recordings.Successful recordings are those in which 58 hexagons (95%) achieved a signal to noise ratio > 1.7 (our established limit for clinical control population).
Currently mfERG testing has been attempted on 12 subjects; we could not obtain an acceptable eye position in 2 subjects and one subject was excluded because of poor sedation. Repeat recordings were performed on 3 subjects. Successful recordings were achieved in 60% of cases. Foveal alignment was accurate to within the diameter of 2 hexagons (8o) in all recordings (mean 1.4 hexagons). After realignment of the recordings, paired t-tests showed no significant differences in either amplitude (RMS) or P1 implicit time.
Meaningful mfERG recording can be obtained from infants under 5 years of age using sedation. The effects of sedation on the mfERG waveforms still requires more study. Its use, however allows mfERG techniques to be used to study infant retinopathies and early retinal development.
This PDF is available to Subscribers Only