The ability to resolve single cells noninvasively in the living retina has important applications for the study of normal retina, diseased retina, and the efficacy of therapies for retinal disease. We describe a new instrument for high-resolution, in vivo imaging of the mammalian retina that combines the benefits of confocal detection, adaptive optics, multispectral, and fluorescence imaging. The instrument is capable of imaging single ganglion cells and their axons through retrograde transport in ganglion cells of fluorescent dyes injected into the monkey lateral geniculate nucleus (LGN). In addition, we demonstrate a method involving simultaneous imaging in two spectral bands that allows the integration of very weak signals across many frames despite inter-frame movement of the eye. With this method, we are also able to resolve the smallest retinal capillaries in fluorescein angiography and the mosaic of retinal pigment epithelium (RPE) cells with lipofuscin autofluorescence.

With a simple setup, mainly composed of a low coherence light source and a camera, full-field optical coherence tomography (FF-OCT) allows volumetric tissue imaging. However, fringe washout constrains its use in retinal imaging. Here, we present a novel motion-insensitive approach to FF-OCT, which introduces path-length differences between the reference and the sample light in neighboring pixels using an off-axis reference beam. The temporal carrier frequency in scanned time-domain OCT is replaced by a spatial carrier frequency. Volumetric in-vivo FF-OCT measurements of the human retina were acquired in only 1.3 s, comparable to the acquisition times of current clinically used OCT devices.

To determine absorption coefficients for sodium chloride solution (saline) and balanced salt solution at the 193-and 213-nm laser wavelengths. Methods: Absorption coefficients were obtained for each of the component species found in balanced salt solution. This was achieved by measuring laser pulse transmission through solutions of varying concentration. The experiments were repeated using the 193-nm excimer and 213-nm solid-state laser wavelengths. Results for each species were then used to obtain an overall absorption coefficient and penetration depth for balanced salt solution and 0.9% sodium chloride solution. Results: Absorption coefficients in balanced salt solution for the 193-and 213-nm wavelengths were found to be 140 and 6.9 cm −1 , respectively. In 0.9% sodium chloride solution, the absorption coefficient was 81 cm −1 at 193 nm and 0.05 cm −1 at 213 nm. At 193 nm, absorption in balanced salt solution was dominated by sodium chloride. Sodium citrate emerged as the dominant species of absorption at 213 nm.

Two-photon excitation fluorescence (TPEF) microscopy is a powerful technique for sensitive tissue imaging at depths of up to 1000 micrometers. However, due to the shallow penetration, for in vivo imaging of internal organs in patients beam delivery by an endoscope is crucial. Until today, this is hindered by linear and non-linear pulse broadening of the femtosecond pulses in the optical fibers of the endoscopes. Here we present an endoscope-ready, fiber-based TPEF microscope, using nanosecond pulses at low repetition rates instead of femtosecond pulses. These nanosecond pulses lack most of the problems connected with femtosecond pulses but are equally suited for TPEF imaging. We derive and demonstrate that at given cw-power the TPEF signal only depends on the duty cycle of the laser source. Due to the higher pulse energy at the same peak power we can also demonstrate single shot two-photon fluorescence lifetime measurements. Leproux, "Multicolor multiphoton microscopy based on a nanosecond supercontinuum laser source," J. Biophoton. In press (2016). 10. G. Donnert, C. Eggeling, and S. W. Hell, "Major signal increase in fluorescence microscopy through dark-state relaxation," Nat. Methods 4(1), 81-86 (2007). 11. M. Goeppert-Mayer, "Über Elementarakte mit zwei Quantensprüngen," Ann. Phys. 9(3), 273-294 (1931). ©2016 Optical Society of America #261064Received 11 12. S. Karpf, M. Eibl, W. Wieser, T. Klein, and R. Huber, "A Time-Encoded Technique for fibre-based hyperspectral broadband stimulated Raman microscopy," Nat. Commun. 6, 6784 (2015). 13. S. Tang, J. Liu, T. B. Krasieva, Z. Chen, and B. J. Tromberg, "Developing compact multiphoton systems using femtosecond fiber lasers," J. Biomed. Opt. 14, 030508 (2009). 14. F. Knorr, D. R. Yankelevich, J. Liu, S. Wachsmann-Hogiu, and L. Marcu, "Two-photon excited fluorescence lifetime measurements through a double-clad photonic crystal fiber for tissue micro-endoscopy," J. Biophotonics 5(1), 14-19 (2012). 15. K. Taira, T. Hashimoto, and H. Yokoyama, "Two-photon fluorescence imaging with a pulse source based on a 980-nm gain-switched laser diode," Opt. Express 15(5), 2454-2458 (2007). 16. R. H. Stolen and C. Lin, "Self-phase-modulation in silica optical fibers," Phys. Rev. A 17(4), 1448-1453 (1978). 17. E. P. Ippen and R. H. Stolen, "Stimulated Brillouin scattering in optical fibers," Appl. Phys. Lett. 21(11), 539-541 (1972 478-492 (2010). 21. N. S. Makarov, M. Drobizhev, and A. Rebane, "Two-photon absorption standards in the 550-1600 nm excitation wavelength range," Opt.

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