Factors Affecting Photopic Negative Response Recorded with RETeval System: Study of Young Healthy Subjects

Purpose To determine whether there is a significant correlation between the amplitude of the photopic negative response (PhNR) and the peripapillary retinal nerve fiber layer thickness (pRNFLT) in eyes of young, healthy subjects. Methods We analyzed 136 eyes of 136 young, healthy subjects (89 males and 47 females; age, 20-29 years). The PhNRs were recorded with the RETeval system without mydriasis using red flashes on a blue background. PhNR amplitude was measured at two points: at 72 ms (P72) and at the negative trough following the b-wave (Pmin). Univariate and multivariable linear regression analyses were performed to identify the independent variables that were significantly correlated with P72 and Pmin. The variables included age, sex, axial length, pRNFLT, intraocular pressure (IOP), a-wave amplitude, b-wave amplitude, and pupillary area during the electroretinogram recordings. Results The amplitudes of P72 and Pmin were significantly larger in female subjects (P = 0.021 and P = 0.001, respectively). Univariate analyses showed that PhNR amplitudes were significantly correlated with pRNFLT (P72: r = 0.246, P = 0.004; Pmin: r = 0.219, P = 0.011). Female sex was significantly and negatively correlated with P72 (r = -0.206; P = 0.016) and Pmin (r = -0.271; P = 0.001). Multivariable regression analyses showed that greater pRNFLT was an independent factor significantly associated with a larger P72 (r = 0.283; P = 0.004) and Pmin (r = 0.299; P = 0.002). Female sex was an independent factor that was significantly associated with a larger Pmin (r = -0.208; P = 0.022). Conclusions These findings indicate that PhNR amplitude is significantly associated with pRNFLT and female sex in young, healthy subjects. Translational Relevance The amplitude of the PhNR recorded with RETeval is smaller in subjects with thinner pRNFLT not only in glaucoma patients but also in young healthy subjects.