To investigate whether visual function can be graded in detail using pattern electroretinogram (PERG) in preperimetric to perimetric glaucoma.

Cross-sectional observational study.

Twenty-six normal subjects, 113 preperimetric glaucoma patients (which included glaucoma suspect patients), and 52 early perimetric glaucoma patients with a mean deviation (MD) >−10 dB were included. Structural and functional measurements were performed using spectral-domain optical coherence tomography and a commercial ERG stimulator, respectively.

The average retinal nerve fiber layer (RNFL) and ganglion cell–inner plexiform layer (GCIPL) thickness were thinnest in the perimetric group, followed by the preperimetric group and the control group (P < .001). PERG N95 amplitude was the largest in the control group, followed by the preperimetric group and the perimetric group (P < .001). Among the preperimetric glaucoma patients, presence of the RNFL defect was associated with lower PERG N95 amplitude (P = .013). The N95 amplitude showed a significant relationship with average RNFL thickness (r = 0.336, P < .001) and GCIPL thickness (r = 0.376, P < .001). In the preperimetric group with the RNFL defect, the N95 amplitude showed larger areas under the receiver operating characteristic curve (0.779) than the MD (0.533, P = .005).

PERG N95 amplitudes decreased from the control to preperimetric glaucoma group and were reduced more in perimetric glaucoma. The functional assessment for detecting early glaucomatous damage could be complemented by PERG N95 amplitude. Usefulness of PERG parameters except N95 amplitude seemed to be limited in a clinical setting because of relatively low diagnostic performance in preperimetric glaucoma.