Disclosed are various embodiments for imaging retinal intrinsic optical signals (IOS) in vivo. According to various embodiments, imaging retinal intrinsic optical signals (IOS) may comprise illuminating a host retina with near infrared light (NIR) during a test period, wherein the host retina is continuously illuminated by the NIR light during the test period. Sequentially a host retina may be stimulated with a timed bursts of visible light during the test period. A series of images of the retina may be recorded with a line-scan CCD camera and the images may be processed to produce images of intrinsic optical signals (IOS) from retinal photoreceptor cells identified in the images.
