Wide field visualization of retinal and choroidal microstructure in vivo using frequency domain OCT at 1060 nm with up to 47000 lines/s B. Hermann a , M. Esmaeelpour a,b , B. Povaˇ zay a , B. Hofer a , F. Bounaparte a , Nick Sheen b , Rachel North b , W. Drexler a a Biomedical Imaging Group, School of Optometry & Vision Sciences, Cardiff University, Cardiff CF24 4LU, United Kingdom b Clinical and Investigative Vision Sciences, School of Optometry & Vision Sciences, Cardiff University, Cardiff CF24 4LU, United Kingdom ABSTRACT We present in vivo frequency domain optical coherence tomography of the human retina and choroid in the 1060 nm water transmission window with 72 nm optical bandwidth (<8 μm axial resolution in tissue) and up to 74 frames per second (`a 512 × 512 pixels). A novel InGaAs stripe array with 1024 pixels and 47000 lines/s read out rate is utilized in combination with an all reflective spectrometer to enable densely sampled wide field scans (35 ◦ ×35 ◦ ), i.e. ∼10×10 mm 2 ) acquired in less than 7 seconds. At this speed numerical motion artifact removal algorithms are sufficient to compensate remaining involuntary drifts of the subject’s eye. Enhanced penetration beyond the retina enables for the first time highly isotropically sampled, three-dimensional visualization of all three layers of the choroidal vasculature without the need of contrast agents, the choroidal-scleral interface as well as the first scleral layer, the absorbing lamina fusca sclerae. Furthermore the choroidal thickness was quantified in 30 healthy subjects and correlated with axial eye length. First results indicate an decrease in choroidal thickness with increasing axial eye length. Keywords: Optical coherence tomography, retina, choroid, choroidal vasculature, choroidal thickness, eye length 1. INTRODUCTION Optical coherence tomography 1 (OCT) is a well established technique in ophthalmic imaging, 2–5 mainly utilizing wavelengths around 800 nm, where the water absorption is low and easy access to the retina is possible. With increasing wavelengths the absorption increases, but has a locale minimum around 1060 nm with a value com- parable to 900 nm, the so called water transmission window, which makes imaging at this specific wavelength region more and more interesting. 6–9 Figure 1 compares two Gaussian spectra of the same power, one centered at 800 nm (50 nm bandwidth), the other centered at 1060 nm (70 nm bandwidth). These two spectra should lead to the same axial resolution and correspond to specifications of the actual systems used. After passing 50 mm water (see water absorption, Fig. 1, light blue line) the power for 800 nm is nearly unaltered. For 1060 nm water absorption leaves only 1/4 of the incident power (hatched areas in the spectra). In ophthalmic imaging this loss can be compensated by applying higher power, since exposure limits are higher for longer wavelength. Furthermore scattering is reduced to 1/4 (dark blue line), facilitating the visualization of the choroidal vascular structure. 6, 10, 11 In this paper we present in vivo three-dimensional retinal and choroidal ophthalmic imaging at 1060 nm and compare it to findings at 800 nm. Furthermore we present first results from a study, which correlates choroidal thickness with axial eye length. Corresponding author: W.Drexler: drexlerw@cardiff.ac.uk Ophthalmic Technologies XIX, edited by Fabrice Manns, Per G. Söderberg, Arthur Ho Proc. of SPIE Vol. 7163, 71630A · © 2009 SPIE CCC code: 1605-7422/09/$18 · doi: 10.1117/12.809253 Proc. of SPIE Vol. 7163 71630A-1