Abstract
Purpose: :
It has been shown recently that optical imaging of living retinas at wavelengths longer than 900nm has the dual advantage of improved image penetration in the choroid, and of permitting simultaneous, non-invasive testing of retinal photoreceptor function. Furthermore, high speed data acquisition allows for fast 3D imaging of larger volumes of biological tissue and reduces the effect of imaging artifacts associated with motion of the imaged object. Here we present high resolution 3D images of rat retina, acquired in-vivo from healthy and diseased rats, with a high speed, high resolution OCT system operating in the 1060nm wavelength range.
Methods: :
The imaging system is based on a spectral domain OCT (SD-OCT) design, with no moving parts, which provides high sensitivity and phase stability. The system is fiber based and designed to operate in the 900-1200nm wavelength range. It utilizes a fast 1024 pixel linear array InGaAs CCD camera with 47 kHz readout rate to provide time resolution of 22µs / A-scan. The system is powered by a broad bandwidth CW light source, which provides ~3µm OCT axial resolution in the rat retina, and sensitivity of more than 105dB at 850 µW power of the imaging beam. OCT mages were obtained from both albino (White Start) and pigmented (Long Evans) rats. All animal experiments were conducted in accordance with the "ARVO Statement for Use of Animals in Ophthalmic and Vision Research".
Results: :
High resolution 2D and 3D tomograms acquired with the SD-OCT system show clear visualization of all intra-retinal layers, including the inner and outer photoreceptor segments, as well as the inner and outer limiting membranes. Compared to OCT retinal tomograms acquired in the 800nm wavelength range, retinal images obtained at 1060nmm show increased penetration into the choroid with clear identification of the choroidal blood vessel network. 3D reconstruction of retinal images acquired near the optical disc show the vascular architecture, in some cases including what may be the remnants of the hyaloid vasculature.
Conclusions: :
A novel, high speed, high resolution SD-OCT system, operating in the 1060nm wavelength region was developed and used for fast, in-vivo 3D imaging of healthy and diseased retinas. This imaging system can potentially be used for simultaneous measurement retinal morphology, choroidal blood flow and light induced functional responses in the retina.Support: NSERC, ORDCF, Peter & Louise Walter Retinal Regeneration fund.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • retina • imaging/image analysis: non-clinical