Relationship of blood flow changes of the human optic nerve with neural retinal activity: a new approach to the study of neuro-ophthalmic disorders

Background: The relationship between the flicker-evoked changes in optic nerve blood flow (F-onh) and neural retinal activity was investigated by laser Doppler flowmetry and electroretinogram (ERG), respectively. Material and methods: In five normal subjects F-onh was continuously recorded before, during and after exposure to green flicker modulation (30 Field at the posterior pole), at different levels of mean illuminance between 0.9 and 13.5 lux. During flicker stimulation, ERGs were simultaneously recorded with F-onh. The flicker-evoked changes in F-onh (RFonh) and the amplitudes of the first (1F) and second (2F) harmonic component of the ERG were measured. Results: By increasing mean flicker illuminance, RFonh and ERG 2F, but not 1F amplitude first increased and then saturated beyond 10 lux. RFonh and the corresponding 2F amplitudes, recorded at the various mean illuminances, showed a significant positive correlation (r = 0.79, p < 0.01). Conclusions: Under specific experimental conditions, changes in human RFonh are quantitatively correlated with those of the flicker ERG 2F amplitudes. Since the 2F component reflects, unlike 1F, a strong contribution from inner retina, the present findings support the presence of an association between vasoactivity and inner retinal activity changes in the human eye. This Finding may provide a new approach to the study of neuro-ophthalmic disorders.