Direct Observation of Multiple Functional Intrinsic Signals Induced by Patterned Visible Light Stimuli

Abstract

Purpose:: Retinal reflectance changes in response to stimulation carry information about metabolic processes underlying light responses in the retina. The Retinal Function Imager (RFI, Optical Imaging, Ltd.) was used to non-invasively image induced reflectance changes in monkey and human retina.

Methods:: The RFI measures functional signals in retinal image series recorded at chosen wavelengths. We measured changes in retinal reflectance during 12-second trials with two visual stimulus test patterns and blank as a control. A patterned stimulus flashed once or at 4-30Hz during recording in infrared from eyes of anesthetized monkeys or awake human.

Results:: Multiple intrinsic functional signals were clearly resolved, varying in amplitude and duration and yielding a change of up to 0.5% in retinal reflectance. The extent of the spatially specific response matched the stimulus patterns. Stimulus wavelength, frequency, duration and intensity all strongly affected the signal.

Conclusions:: The measured optical signals provide information about activity-dependent metabolic processes in the retina. The localized signals also provide an objective indicator of retinal function, suggesting clinical applications.

Keywords: retina • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • photoreceptors