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K. Venkateswaran, F. Romero-Borja, A. Roorda, T.J. Hebert; Axial Resolution of the Adaptive Optics Scanning Laser Ophthalmoscope: Model vs. Experiment . Invest. Ophthalmol. Vis. Sci. 2003;44(13):3622.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Adaptive optics (AO) for optical wavefront correction and confocal imaging in the scanning laser ophthalmoscope (AOSLO) has resulted in higher lateral and axial resolution with the confocal scanning laser ophthalmoscope. Our purpose was to develop a method to quantify the in vivo axial resolution of the AOSLO and compare with theoretical predictions based on a mathematical model of the AOSLO. Methods: A model of the AOSLO was developed to predict axial resolution. This model was used to estimate the best axial resolution for a diffraction-limited eye and for 8 subjects after AO correction. The model was also used to determine the effect of misaligned optics, uncorrected modes and measurement errors on axial resolution. Experimental axial resolution measurements were done in vivo in three subjects at different retinal locations. AOSLO measured and compensated aberrations of the eye in a 1.5 X 1.4 deg area of the retina, at a frame rate of 30Hz. Different retinal planes were imaged by applying defocus using the deformable mirror. The axial resolution was estimated as the full-width at half height of the integrated intensity of a retinal feature. Results: The model predicts the axial resolution in 8 subjects with residual aberrations to vary between 119 to 146 microns and 112 microns for a diffraction-limited eye. The experimental axial resolution in our 3 subjects varied from 155 to 194 microns. The difference between model and experiment are possibly due to unmeasured aberrations, non-common path errors, or scattering in the optics of the eye and instrument, none of which were included in the computational model. The model shows axial resolution improvement of the AOSLO can be obtained by reducing the pinhole size, but would result in decreased detected light levels and hence a lower signal to noise ratio in the images. Conclusions: Experimental axial resolution lies within the axial resolution predicted by the model. From these results we calculate our best volume resolution to be 761 µm3, which approaches an order of magnitude improvement over conventional SLO instruments. This demonstrates the capability of the AOSLO to optically slice retinal tissue in vivo.
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