Significant correlations between photopic negative response, afferent pupillary defect, and mean defects of visual...

The photopic negative response (PhNR) is a negative wave following the b-wave of the photopic electroretinogram (ERG). The PhNR originates from the retinal ganglion cells (RGCs), and it can be used to assess the function of RGCs noninvasively and objectively. The purpose of this study was to determine whether the relative amplitudes (affected/normal eye) of the PhNR are significantly correlated with the degree of the relative afferent pupillary defect (RAPD) in eyes with unilateral or asymmetrical damage of the optic nerve.

The PhNRs of the full-field photopic ERGs were measured. In addition, videopupillography and automated perimetry were performed on 27 cases with asymmetrical optic nerve disorders including glaucoma. The differences of these assessments were expressed by the relative amplitudes of the PhNRs of the two eyes, the neutral density (ND) filter required to equate the amplitudes of the pupillary light reflexes between the two eyes, and differences of the mean defects (ΔMDs) of the sensitivities of the Humphrey visual fields. The correlations between these values were determined by linear regression analyses.

The relative PhNR amplitudes were significantly and negatively correlated with the ΔMDs (R² = 0.58, P = 0.0001). In addition, the relative PhNR amplitudes were moderately but significantly and positively correlated with the RAPDs (R² = 0.36, P = 0.002).

The relative amplitudes of the PhNR of the affected eyes to the contralateral eyes indicate an asymmetric alteration of the RGCs, and they can be used to monitor the physiology of the RGCs objectively.