Purpose:
To investigate the influence of the scanning angle on the wave front correction and therefore the quality of images of the human retina acquired in vivo with an adaptive optics scanning laser ophthalmoscope (AO-SLO).
Methods:
In this study a custom built, lens based AO-SLO instrument operating at a frame rate of 10 fps (scanning angle 1°x1°, 3°x3°, 4°x4° and 5°x5°) is used to record images of the human cone mosaic. The adaptive optics system is operated in closed loop and uses part of the imaging light for wave front sensing. To increase the signal to noise ratio 30 images are registered to each other and averaged prior to data analysis. A possible advantage of the lens based system is that aberrations introduced by the system itself during scanning are reduced in comparison with instruments based on spherical mirrors. The image quality of the same retinal region using different scanning angles is compared.
Results:
The figure shows representative images recorded from the fovea region in a healthy volunteer. The 4 degree scanning angle shows very similar image quality as images recorded with 1 degree (c.f. comparison of the ROI on the right hand of the figure). The cone mosaic could be resolved down to an eccentricity of 0.25° from the fovea centralis.
Conclusions:
Similar image quality could be obtained using large scanning angles of up to 4 degrees in healthy subjects. The larger scanning angles reduce artifacts caused by eye motion and the total measurement time, which should allow a broader use of AO-SLO in healthy subjects and patients.
Keywords: photoreceptors • imaging/image analysis: non-clinical • retina