Development of a versatile stereo scanning laser ophthalmoscope

The scanning laser ophthalmoscope (SLO) is a modern tool which is now widely used to image the fundus of the eye, particularly for assessment of the optic nerve head. We describe a modified SLO capable of producing stereo pairs of the optic disk in real time. A pair of toggling mirrors is used to switch between entry positions of the scanned laser beam into the pupil of the eye thereby creating a stereo base for capturing the two different views required for the pair. Our laboratory prototype is constructed from reflective optics only in the bi-directional part of the beam path, including the focusing and beam shaping unit. Thus, we avoid unwanted back reflections and chromatic aberrations. Light from different laser sources (458 to 1100 nm) can be launched into the SLO, also simultaneously. Collimated beams in beam splitting locations allow for easy modifications. Imaging in fluorescence mode or polarization dependent imaging is also possible. High quality multi-wavelengths stereo pairs of both model and real optic disks were obtained. a lateral resolution of up to 6 micrometer and an axial resolution of up to 65 micrometer was established.