Dual SLO/T-scan based en face ultrahigh resolution OCT for ophthalmic imaging

Abstract

We report a versatile imaging system combining scanning laser ophthalmoscopy (SLO) and T-scan based en face ultrahigh resolution optical coherence tomography (OCT). The image carrier is generated using the optical path difference modulation introduced by the X-Y galvo-scanner mirrors specific to en face OCT (without optical modulators in the reference arm). The light source is a compact superluminescent diode based source with 150 nm FWHM spectrum, centered at 890 nm. We demonstrate en face B-scan and C-scan ultrahigh resolution OCT imaging of the human retina in vivo, with an axial resolution of 3.2 μm in tissue. The system is capable of acquiring large lateral size ultrahigh resolution OCT scans of a maximum field size of 20°. The acquisition speed is up to 2 frames/s for both OCT B-scans and C-scans. The measured system sensitivity is more than 98 dB, for a power level to the target of 1 mW and maximum lateral scan size. The C-scans are, to the best of our knowledge, the first and the largest size reported ultrahigh resolution C-scans of the human retina in vivo. The instrument is assembled on a chin rest and ready to be used for clinical imaging. SLO and ultrahigh resolution OCT C-scans are acquired simultaneously and displayed side by side. This allows users in a clinical environment to correlate details of the same feature in the area of interest in both images and also choose precisely in the SLO image the location where to perform the ultrahigh resolution en face B-scan.