Functional optical coherence tomography reveals transient phototropic change of photoreceptor outer segments

Abstract

Dynamic near infrared microscopy has revealed transient retinal phototropism (TRP) correlated with oblique light stimulation. Here, by developing a hybrid confocal microscopy and optical coherence tomography (OCT), we tested sub-cellular source of the TRP in living frog retina. Dynamic confocal microscopy and OCT consistently revealed photoreceptor outer segments as the anatomic source of the TRP. Further investigation of the TRP can provide insights in better understanding of Stiles–Crawford effect (SCE) on rod and cone systems, and may also promise an intrinsic biomarker for early detection of eye diseases that can produce photoreceptor dysfunction.

Stimulus-evoked outer segment changes occur before the hyperpolarization of retinal photoreceptors

“…The methods employed for the quantification of ROS movements and the segmentation of active areas were as described previously [2]. An optical flow algorithm [18] was employed to generate a movement magnitude map (Figs.…”

“…Because the previous and present studies differ in several respects, including the investigation of intact eye vs. isolated retina, OCT vs. microscopy system, and possible differences in photo stimulation efficiency, the extent to which the presently measured ROS movement accounts for the previously measured overall IOS remains to be determined. For isolated retina, this issue can be addressed in future work by using either a camera with higher frame acquisition rate, or other high-speed imaging techniques such as high-speed confocal [10, [20][21][22] or OCT [2,11] systems.…”

“…High-resolution microscopy revealed that the TRP is dominated by rod photoreceptors. Functional optical coherence tomography (OCT) located the anatomic source to rod outer segment (ROS) [2]. Our recent studies with retina slices, which enable a cross-sectional view of mouse and frog photoreceptors, confirmed the ROS movement as the physical mechanism of TRP [3].…”

“…The isolated retina was continuously superfused with physiological medium during the experiment. (B) The retina was placed with photoreceptor layer on the top and was obliquely (~20°) stimulated by visible light from the top [2]. The coordinate axes shown at the bottom were used to define the direction of ROS movement.…”

In vivooptical coherence tomography of stimulus-evoked intrinsic optical signals in mouse retinas

“…11 These studies also revealed that photoreceptor IOSs had a rapid time course (<4 ms after onset of the light stimulus). 13,28 Transient retinal phototropism was reported to be one factor that generates photoreceptor IOSs, [31][32][33] but the IOS physiological source has not been accurately determined yet. Before pursuing clinical applications, it is necessary to establish the relationship between IOS distortions and eye diseases.…”