Purchase this article with an account.
Y. K. Tao, W. Choi, J. A. Izatt; Enhanced-resolution Retinal Imaging Using Structured Illumination Line-scanning Laser Ophthalmoscopy. Invest. Ophthalmol. Vis. Sci. 2009;50(13):3802.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Advances in adaptive optics (AO) systems, such as AO flood illumination, AO scanning laser ophthalmoscopy (AOSLO), and AO optical coherence tomography (AOOCT), have allowed for the compensation of aberrations introduced by the human eye, which enable imaging of cone photoreceptors. These systems, which provide high-resolution images of human retinal tissue, are limited to a <2.5deg field of view and by the complex and expensive optical components common to all AO systems, such as wavefront sensors, deformable mirrors, and large optical layouts. Advances in structured illumination have shown resolution doubling in microscopy. These techniques impose a spatial frequency carrier by illuminating the sample with a grating pattern, which down-shifts the high-frequency components of the sample. This down-shifting increases the spatial frequency bandwidth allowed by the optical transfer function, thus overcoming the resolution limit of the imaging system. Here, we demonstrate a structured illumination line-scanning laser ophthalmoscope (SILSLO), which combines the resolution improvement of structured illumination with the depth-selectivity and contrast improvement of a quasi-confocal line-scanning laser ophthalmoscope.
SILSLO was implemented on custom-built LSLO. The structured illumination pattern was created by interfering the ±1 orders of a transmission grating at the focal plane for each scan-line. Scanning in the direction orthogonal to the illumination line creates a grating pattern at the sample, thus allowing higher spatial resolution to propagate through the system.
Structured illumination resolution improvement was demonstrated using a USAF 1951 test chart (Fig. 1) placed in the focal plane of a simulated eye with a 25mm lens and 3mm aperture. A contrast cross-section of Group 5 Element 5 between the LSLO and SILSLO images shows a factor of 1.59 improvement in resolution (Fig. 1(e)).
Resolution improvement has been demonstrated using a modified LSLO system. Since the structured illumination was adapted to a LSLO designed for retinal imaging, the resolution improvement can be directly applied to fundus imaging.
This PDF is available to Subscribers Only