Temporal changes of human cone photoreceptors observed in vivo with SLO/OCT

In this study we use our previously introduced scanning laser ophthalmoscope (SLO) / transverse scanning optical coherence tomography (TS-OCT) instrument to investigate long term changes in cone photoreceptors. The instrument is capable to provide 3D information of the human cone photoreceptors with negligible eye motion artifacts due to an implemented 3D motion correction on a cellular level. This allows for an in vivo investigation of exactly the same location on the retina with cellular resolution over several days. Temporal changes in the backscattered intensity are observed and quantified within the junction between inner and outer segments of cone photoreceptors, the cone outer segments, the end tips of cone photoreceptors and the retinal pigment epithelium. Furthermore, the length of individual cone outer segments is measured and observed over time. We show, to the best of our knowledge for the first time, that bright reflection spots which are located within the outer segment of cone photoreceptors change their position when observed over extended time periods. The average measured bright reflection spot motion speed corresponds well to the expected cone growth speed. We believe that this observation can be associated with the first direct in vivo imaging of the cone renewal process.