It is well established that major retinal diseases involve distortions of the retinal neural physiology and blood vascular
structures. However, the details of distortions in retinal neurovascular coupling associated with major eye diseases are
not well understood. In this study, a multi-modal optical coherence tomography (OCT) imaging system was developed
to enable concurrent imaging of retinal neural activity and vascular hemodynamics. Flicker light stimulation was applied
to mouse retinas to evoke retinal neural responses and hemodynamic changes. The OCT images were acquired
continuously during the pre-stimulation, light-stimulation, and post-stimulation phases. Stimulus-evoked intrinsic optical
signals (IOSs) and hemodynamic changes were observed over time in blood-free and blood regions, respectively. Rapid
IOSs change occurred almost immediately after stimulation. Both positive and negative signals were observed in
adjacent retinal areas. The hemodynamic changes showed time delays after stimulation. The signal magnitudes induced
by light stimulation were observed in blood regions and did not show significant changes in blood-free regions. These
differences may arise from different mechanisms in blood vessels and neural tissues in response to light stimulation.
These characteristics agreed well with our previous observations in mouse retinas. Further development of the multimodal
OCT may provide a new imaging method for studying how retinal structures and metabolic and neural functions
are affected by age-related macular degeneration (AMD), glaucoma, diabetic retinopathy (DR), and other diseases,
which promises novel noninvasive biomarkers for early disease detection and reliable treatment evaluations of eye
In conventional fundus imaging devices, transpupillary illumination is used for illuminating the inside of the eye. In this method, the illumination light is directed into the posterior segment of the eye through the cornea and passes the pupillary area. As a result of sharing the pupillary area for the illumination beam and observation path, pupil dilation is typically necessary for wide-angle fundus examination, and the field of view is inherently limited. An alternative approach is to deliver light from the sclera. It is possible to image a wider retinal area with transcleral-illumination. However, the requirement of physical contact between the illumination probe and the sclera is a drawback of this method. We report here trans-palpebral illumination as a new method to deliver the light through the upper eyelid (palpebra). For this study, we used a 1.5 mm diameter fiber with a warm white LED light source. To illuminate the inside of the eye, the fiber illuminator was placed at the location corresponding to the pars plana region. A custom designed optical system was attached to a digital camera for retinal imaging. The optical system contained a 90 diopter ophthalmic lens and a 25 diopter relay lens. The ophthalmic lens collected light coming from the posterior of the eye and formed an aerial image between the ophthalmic and relay lenses. The aerial image was captured by the camera through the relay lens. An adequate illumination level was obtained to capture wide angle fundus images within ocular safety limits, defined by the ISO 15004-2: 2007 standard. This novel trans-palpebral illumination approach enables wide-angle fundus photography without eyeball contact and pupil dilation.
High resolution is important for sensitive detection of subtle distortions of retinal morphology at an early stage of eye diseases. We demonstrate virtually structured detection (VSD) as a feasible method to achieve in vivo super-resolution ophthalmoscopy. A line-scanning strategy was employed to achieve a super-resolution imaging speed up to 127 frames/s with a frame size of 512×512 pixels. The proof-of-concept experiment was performed on anesthetized frogs. VSD-based super-resolution images reveal individual photoreceptors and nerve fiber bundles unambiguously. Both image contrast and signal-to-noise ratio are significantly improved due to the VSD implementation.