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M. E. Harris, R. M. Hansen, A. Moskowitz, A. M. Barnaby, A. B. Fulton; Rod and Rod-Driven Electroretinogram (ERG) Response Parameters Obtained Using Skin Electrodes. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2227.
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Very young children may not readily tolerate a corneal contact electrode. Therefore, we evaluated skin electrodes for estimation of rod photoreceptor and post-receptor function in pediatric research subjects.
ERGs were recorded from 30 subjects using skin electrodes: 14 children with a history of preterm birth (age at test, 3 to 9 years); 6 term born children (4 to 12 years); and 10 older term born subjects (13 to 64 years). The 10 oldersubjects were also tested using Burian-Allen contact electrodes. ERG responses to a >4 log unit range of blue flashes were recorded from dark-adapted subjects. Rod photoreceptor sensitivity (S) and saturated amplitude (R) were calculated from the a-wave, and post-receptor sensitivity (log σ) and saturated amplitude (VMAX) were calculated from the b-wave.
Frequent instruction to keep the eye open and increased signal averaging of the noisier traces were required to obtain acceptable responses, causing skin electrode ERG sessions to tend to be longer than our typical Burian-Allen sessions. Nonetheless, skin electrode ERGs were adequate for estimation of post-receptor parameters, log σ and VMAX, from all 30 subjects and of rod response parameters, S and R, from all but three. In the 10 control subjects tested with both electrode types, rod sensitivity (S) and post-receptor sensitivity (log σ) did not differ between ERGs recorded with skin and corneal contact electrodes, but saturated amplitudes (R, VMAX) of the skin electrode ERGs were significantly smaller, only about 18% of the amplitudes obtained using corneal contact electrodes. Skin electrode ERG parameters in preterm subjects did not differ significantly from those in term born subjects.
Scotopic sensitivity parameters can be determined from ERG records obtained using skin electrodes. Thus, this method appears applicable to studies of retinal processes in cooperative, young research subjects, such as those with a history of ROP, who cannot be reasonably studied with contact electrodes. However, the small recorded amplitudes may limit the clinical utility of skin electrodes.
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