Abstract
Purpose :
mfERG testing is used to study the function of cone photoreceptors in the central retina. mfERG analysis software offers methods for applying "smoothing" (Smooth) and “adaptive data filtering” (Adapt) to ERG waveforms. These modifiers are available on a sliding scale of increasing intensity from 1 to 4, yet the effects of these mfERG filters have yet to be characterized. It is possible this data modification affects the study outcomes reported on the “normal reference” and “normal deviation” reports, impacting eventual study interpretation. This study will seek to characterize the effect of data modification on raw patient data. Our study will inform the use of these modification algorithms in the future analysis of mfERG results.
Methods :
This was a retrospective study including patients with mfERG testing at our institution. For each patient, raw mfERG data without filtering, with smooth level 4 modifier applied, and with adapt level 4 applied were collected. Data for P1 latency and P1 amplitude were analyzed from all 61 mfERG hexagons and compared between these 3 filters. Subgroup analysis included comparisons between peripheral and central two mfERG rings as well as studies interpreted as “abnormal” versus “normal” clinically.
Results :
20 patients were sampled (40 eyes), 6 males and 14 females with a mean age of 56.82 years. 10 patients (50%) had “normal” mfERGs and 10 patients (50%) had “abnormal” mfERGs. Smooth 4 decreased P1 latency by -2.18 +/- 0.50 ms (5.78% +/- 1.31%, p <0.001) while Adapt 4 decreased P1 latency by -2.39 +/- 0.51 ms (6.30% +/- 1.14%, p <0.001). Smooth 4 decreased P1 amplitude by -183.54 +/- 9.12 nV (32.0% +/- 1.60%, p <0.001) while Adapt 4 decreased P1 amplitude by -210.59 +/- 14.58 nV (53.9% +/- 3.73%, p <0.001). While there was no significant difference between the P1 latency in Smooth 4 and Adapt 4 groups, there was a significant decrease in P1 amplitude when smooth 4 was compared with adapt 4 (-27.05 nV, p <0.001).
Subgroup analysis of the peripheral mfERG ring and central 2 mfERG rings is summarized in Table 1. Subgroup analysis of clinically normal mfERG studies and clinically abnormal mfERG is summarized in Table 2.
Conclusions :
Smoothing and adaptive filter modifiers create statistically significant differences in both P1 latency and P1 amplitude compared to raw data, which should impact physicians’ decision making when interpreting mfERG results.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.