Abstract
Purpose :
The purpose of this study was to evaluate the effect of spatial averaging on the multifocal electroretinography (mfERG) averaged ring peak times in patients screened for hydroxychloroquine (HCQ) toxicity.
Methods :
This was a retrospective review of the records of patients screened for HCQ retinopathy at the USF Eye Institute (University of South Florida) during the period of 2015-2020. Only the records of patients referred internally were used. Patients were tested binocularly with Diagnosys mfERG system (Diagnosys LLC, Lowell, MA) using 61 hexagons grouped in 5 rings. The effects of the lowest level (level 1, or 4%) of spatial averaging on the mfERG N1, P1 and N2 peak times ring averaged values were evaluated.
Results :
The records of 40 patients (4 males, 36 females) aged 54.4 ± 14.1 yrs. were selected for analysis. The use of spatial averaging had a differential effect on different rings and mfERG components. Thus, for N1 peak times, only a small, but statistically significant effect was detected for ring #1 (central element): -0.29 ± 0.57 ms right eyes (RE) and -0.54 ± 1.34 ms left eyes (LE)(p<0.01), while the timing for the other rings was unaffected. In contrast, for the P1 component ring #2 peak time was affected (-0.18 ± 0.43 ms / -0.18 ± 0.47 ms RE/LE; p<0.05) and additionally the timing for ring #1 in right eyes (-0.23 ± 0.51 ms; p<0.01) and for ring #4 in left eyes -0.23 ± 0.48 ms; p<0.01, one sample Wilcoxon test). No significant changes were observed for the N2 component timing as a group, although in individual cases the change in timing varied from -20.6 to +18.3 ms. The magnitude of change in timing was strongly correlated with the percent change in timing due to spatial averaging for N1 for rings #1 to #4 (R2 0.20 to 0.33), while such a correlation was less pronounced for P1 (rings #1 to #3 RE, #1 & #4 LE; R2 0.11 to 0.44) and for N2 (rings #1, #3, #4 RE, rings #2 & #3 LE; R2 0.12 to 0.19).
Conclusions :
The application of low-level spatial averaging during mfERG analysis can affect the peak times of mfERG components in various ways and given the generally narrow margin of normative values for mfERG peak times, can introduce bias in the results. Therefore, such approach should be strongly discouraged in HCQ toxicity screening mfERG analysis.
This is a 2021 ARVO Annual Meeting abstract.