Abstract
Purpose :
The purpose of this study was to examine the effect of digital filtering on multifocal electroretinography (mfERG) parameters of patients sent for Plaquenil maculopathy screening.
Methods :
This was a retrospective review of patients’ records for patients that underwent HCQ maculopathy screening between December 2014 and October 2019 at USF Eye Institute, Tampa, FL. Only patients who underwent multifocal electroretinography (mfERG) were included. Recording of mfERG was performed binocularly on Espion mfERG system (Diagnosys LLC: Lowell, MA) with DTL electrodes using 61 hexagons stimulus, according to ISCEV mfERG standards. Each recording was subjected to four levels of digital bandpass (FFT/Adaptive) filtering: Level 1 (10-100 Hz), Level 2 (10-90 Hz), Level 3 (10-80 Hz) and Level 4 (10-60 Hz); spatial averaging was tuned off. The effect of filtering was evaluated on grouped ring averages (P1 amplitude) and the results were compared between Level 1 and the other levels of filtering by Dunn's multiple comparisons test.
Results :
The retrospective review identified the records of 40 patients (4 males, 36 females), aged 54.7 +/- 14.1 years. Level 4 filtering induced significant decrease in P1 amplitudes compared to Level 1 for all rings (p>0.001); Level 2 filtering did not cause a significant decreased (p>0.05), while Level 3 filtering caused a significant decrease in ring #1 and ring #2 for left eyes (p<0.05), but not in the other rings. Amplitude reduction associated with Level 4 filtering was most pronounced in ring #1 (~10%), while it was less pronounced for the rest of the rings (4.9%-5.7%). When percent difference between P1 amplitude decrease was plotted vs. P1 amplitude values, an interesting pattern emerged: there was a clear negative correlation between amplitude reduction and amplitude for rings #1 to #3 (Level 3 and 4), while it was present only for ring #3 at Level 2. No correlation was observed for rings #4 and #5 at any level of filtering. This result could be clinically important as it indicates that digital filtering has the most pronounced effect at lowest level of amplitudes, where it could be most useful.
Conclusions :
The results of this study indicate that careful consideration should be given to digital filtering when evaluating the amplitudes of mfERG recordings for Plaquenil maculopathy screening. Future analysis will expand to effects on timing.
This is a 2021 ARVO Annual Meeting abstract.