To the Editor.
—It was with great interest that I read the article by Bresnick and al1 on the predictive values of the oscillatory potentials (OPs) in diabetic retinopathy. I was somewhat disappointed by the great variability (Table 2) of the results obtained. It is my feeling that the observed variability could have been significantly reduced if the authors had made use of a high-pass filter set at 100 cycles per second (cps), rather than the 20 cps used. As mentioned in their article, the frequency components of the electroretinogram are in the 25-cps range for the a and b waves and in the 140-cps range for the OPs. Thus, a low-frequency cutoff set at 20 cps still passes a great deal of both a and b waves, as witnessed in Fig 3. Furthermore, the latter situation makes OP amplitude measurements much more difficult since, as previously acknowledged,2
Lachapelle P. Oscillatory Potentials. Arch Ophthalmol. 1985;103(4):480. doi:10.1001/archopht.1985.01050040022009