Glaucomatous damage to inner retina detected by the flicker ERG second harmonic: losses as a function of temporal frequency

The electroretinogram to flicker stimulation (FERG) consists of two main co mponents: a fundamental (1F) at the same temporal frequency (TF) as the sti mulus and a second harmonic (2F) at twice the stimulation frequency The 2F is generated in the retina more proximally than the 1F and, unlike the 1F c an be significantly altered in ocular hypertension and open angle glaucoma (OAG). This study evaluated the FERG 2F as a function of TF in OAG patients and age-matched controls. The results show that, in patients, the 2F ampli tude losses were consistently found at different TFs both in the low (8-10 Hz! and high (38-40 Hz) regions of the spectrum, with optimal sensitivity a t 8-10 Hz (70%) of the eyes). These data suggest that the FERG 2F recorded at the optimal TFs may be of c omplementary clinical use as support to a glaucoma diagnosis in patients wi th optical media opacities in whom most of the current functional or morpho logic tests of optic nerve integrity cannot be reliably performed.