Purpose:
To test the ability of an adaptive optics scanning laser ophthalmoscope (AOSLO) to image the human nerve fiber layer, and construct a large scale map of the nerve fiber layer. To better understand how the nerve fiber layer is formed by imaging regions with sparse nerve fibers at high resolution.
Methods:
The nerve fiber layer of three human subjects was imaged by a dual deformable mirror AOSLO. This system incorporates both a BMC MEMS DM and a magnetic Mirao 52d DM as well as a Shack Hartmann sensor. Illumination for imaging and wavefront sensing was obtained from a supercontinuum laser (Fianium) with an 840nm filter used in the imaging beam and a 740 nm filter used for the wavefront beacon. The system allows rapid acquisition of small field images across the eye by using displacement mirrors which can place the imaging field of 2.0ºby1.5º within a 30 degrees region of the retina. The traversal-resolution of the system was approximately 3microns depending on the exact pupil size of the subject.
Results:
A montage of the nerve fiber layer 13ºby 10º area was constructed, starting from the nasal side to the temporal side including both superior and inferior retina. Similar but smaller fields were imaged for the other subjects. The data shows that while the nerve fibers are well demarcated and have a side-by-side structure near the optic nerve, they are less well ordered as the nerve fiber layer emerges from the horizontal raphe. Near the raphe we were able to see fiber bundles smaller than 10 microns. In numerous places smaller bundles could be imaged separating from one bundle, crossing a gap where there were not nerve fiber bundles, then joining a separate bundle (see Figure1). The capillaries supplying the nerve fiber layer were also readily imaged.
Conclusions:
The AOSLO allows detailed mapping of the human nerve fiber layer, and can produce high magnification scans of the nfl over significant regions of retina. The wide-field system has the ability to get the large scale montage without changing the fixation target position during the experiment.
Keywords: retinal connections, networks, circuitry • retina