The technique described here is useful for a precise description of FPA and the movement of ocular tissues. Further investigations and technical improvements will be beneficial for understanding the role of choroidal pulsation in the pathophysiology of ocular diseases.

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Recent studies have shown that ocular hemodynamics and eye tissue biomechanical properties play an important role in the pathophysiology of glaucoma. Nevertheless, better, non-invasive methods to assess these characteristics in vivo are essential for a thorough understanding of degenerative mechanisms. Here, we propose to measure ocular tissue movements induced by cardiac pulsations and study the ocular pulse waveform as an indicator of tissue compliance. Using a novel, low-cost and non-invasive device based on spectral-domain low coherence interferometry (SD-LCI), we demonstrate the potential of this technique to differentiate ocular hemodynamic and biomechanical properties. We measured the axial movement of the retina driven by the pulsatile ocular blood flow in 11 young healthy individuals, 12 older healthy individuals and 15 older treated glaucoma patients using our custom-made SD-OCT apparatus. The cardiac pulse was simultaneously measured through the use of an oximeter to allow comparison. Spectral components up to the second harmonic were obtained and analyzed. For the different cohorts, we computed a few parameters that characterize the three groups of individuals by analyzing the movement of the retinal tissue at two locations, using this simple, low-cost interferometric device. Our pilot study indicates that spectral analysis of the fundus pulsation has potential for the study of ocular biomechanical and vascular properties, as well as for the study of ocular disease.

The investigation of the regenerative response of the neurons to axonal injury is essential to the development of new axoprotective therapies. Here we study the retinal neuronal RGC-5 cell line after laser transection, demonstrating that the ability of these cells to initiate a regenerative response correlates with axon length and cell motility after injury. We show that low energy picosecond laser pulses can achieve transection of unlabeled single axons in vitro and precisely induce damage with micron precision. We established the conditions to achieve axon transection, and characterized RGC-5 axon regeneration and cell body response using time-lapse microscopy. We developed an algorithm to analyze cell trajectories and established correlations between cell motility after injury, axon length, and the initiation of the regeneration response. The characterization of the motile response of axotomized RGC-5 cells showed that cells that were capable of repair or regrowth of damaged axons migrated more slowly than cells that could not. Moreover, we established that RGC-5 cells with long axons could not recover their injured axons, and such cells were much more motile. The platform we describe allows highly controlled axonal damage with subcellular resolution and the performance of high-content screening in cell cultures.

In this work we demonstrate the use of two-dimensional detectors to improve the signal-to-noise ratio (SNR) and sensitivity in spectral-domain phase microscopy for subnanometer accuracy measurements. We show that an increase in SNR can be obtained, from 82 dB to 105 dB, using 150 pixel lines of a low-cost CCD camera as compared to a single line, to compute an averaged axial scan. In optimal mechanical conditions, phase stability as small as 92 μrad, corresponding to 6 pm displacement accuracy, could be obtained. We also experimentally demonstrate the benefit of spatial-averaging in terms of the reduction of signal fading due to an axially moving sample. The applications of the improved system are illustrated by imaging live cells in culture.

There was an approximately 11-μm pulsatile change in the ADRC in normal subjects, and on the nasal side of the disc, this amount was significantly greater in glaucoma patients.

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