ObjectiveTo observe the electroretinogram (ERG) photopic negative response (PhNR) of idiopathic macular hole (IMH) in stage 2 by vitrectomy with or without internal limiting membrane peeling (ILMP).MethodsTwenty-three stage 2 IMH patients (23 eyes) were enrolled in this prospective study. All patients received the best corrected visual acuity (BCVA), optical coherence tomography and flash-ERG examinations. The patients were randomly divided into group A (11 eyes, vitrectomy) and B (12 eyes, vitrectomy with ILMP). There was no significant difference in BCVA (t=0.96, P=0.350), diameter of macular hole (MH) (t=3.21, P=0.580) and the PhNR amplitude (t=0.98, P=0.353) in group A and B. All patients underwent 25G vitrectomy, ILMP was carried out in group B. The follow-up time was 3 to 6 months, with the mean follow-up time of 4.3 months. BCVA, MH closure rate and PhNR amplitude in group A and B were analyzed before and after surgery.ResultsThree months after surgery, 10 eyes (90.9%) gained MH closure but 1 eye (9.1%) failed in group A. In group B, 12 eyes (100.0%) gained MH closure. There was no significant difference in MH closure rate between the two groups (P=0.462). The mean BCVA of group A and B was 0.69±0.24 and 0.65±0.22, there was no significant difference between the two groups (t=0.49, P=0.722). The amplitude of PhNR in group A was (36.6±7.4) μV, which was lower than the pre-surgery PhNR, but the difference was not significant (t=0.73, P=0.472). The amplitude of PhNR in group B was (27.1±12.4) μV, which was lower than that the pre-surgery PhNR, and the difference was significant (t =3.56, P =0.002). The difference of PhNR amplitude in group A and B was statistically significant (t=2.17, P=0.042).ConclusionCompared with non-ILMP, vitrectomy combined with ILMP will significantly reduce the PhNR amplitude of IMH in stage 2.