Abstract
Purpose:
To calculate the sensitivity and specificity of multifocal electroretinography (mfERG) in detection of chloroquine (CQ) and hydroxychloroquine (HCQ) retinal toxicity and to find the relationship between the cellular mechanisms of toxicity and clinically recordable abnormalities of retinal electrophysiology testing. A cross sectional study was performed on patients referred for screening of CQ and HCQ retinal toxicity.
Methods:
The results of 10-2 Humphrey automated visual field (10-2 AVF), fundus auto fluorescence (FAF), spectral domain optical coherence tomography (sdOCT) and mfERG were recorded in 120 eyes of 63 patients taking HCQ or CQ. Mean age was 60.06 years. The results of sdOCT and mfERG were also obtained from an age and sex-matched control group of subjects of mean age of 56 years that did not have any known autoimmune disease and never received CQ or HCQ. A combination of 10-2 AVF and sdOCT results was used as the reference test for the calculation of mfERG sensitivity and specificity. Correlation between the HCQ cumulative dose and 10-2 AVF mean deviation (MD), pattern standard deviation (PSD), sdOCT macular thickness, mfERG implicit time, and P1 amplitude R5 ring ratios was investigated using linear regression analysis.
Results:
The sensitivity and specificity of mfERG relative to the reference test were 87% and 86.5% respectively. The “false positive” group exhibited significantly reduced mfERG P1 amplitude R5 ring ratios compared to the normal group in the parafoveal ring 2 (P<0.0002). This difference was not observed in other rings. The abnormal mfERG group also exhibited significantly reduced P1 amplitude R2/R5 (P<0.0001) and R3/R5 (P<0.0002) compared to the normal group. HCQ cumulative dose was negatively correlated with all of the mfERG P1 amplitude R5 ring ratios, but the correlation was strongest in ring 2 (P<0.0006). There was no statistically significant correlation between HCQ cumulative dose and any of 10-2 AVF mean deviation (MD), pattern standard deviation (PSD), or average sdOCT thickness.
Conclusions:
mfERG is more sensitive than the combination of 10-2 AVF and sdOCT in early detection of CQ/HCQ retinal toxicity. There is a relationship between clinically recordable electroretinal dysfunction and the cellular disturbances resulting from accumulation of CQ and HCQ in the retinal neurons.