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N. Doble, S. Choi; Widefield Imaging of the Human Retina Using Adaptive Optics. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1062.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the limitations of high resolution imaging in the human eye for fundus cameras employing adaptive optics (AO). Most flood illuminated AO fundus cameras have a field of view (FOV) of approximately 1 degree (300 microns) on the retina. This is for two main reasons (i) the requirement for the imaging cameras to have enough pixels for sufficient sampling of the cone mosaic (ii) the isoplanatic patch size of the eye which is assumed to be on the order of 1 degree.
We have designed and constructed a flood illuminated AO fundus camera with a 3 degree FOV. The system uses a superluminescent diode at 830nm for the Shack-Hartman wavefront sensor beacon and a diode source at 680nm as the imaging source. The system uses a 37 segment microelectromechanical systems (MEMS) deformable mirror as the wavefront corrector. Subject’s head movements were stabilized through the use of a bite bar and their pupils dilated to provide the required 6mm pupil diameter for the AO system. Repeated 3 degree FOV images were acquired on several subjects.
The images were registered together using a cross correlation algorithm to improve the signal to noise. The registered images were then examined using power spectrum analysis to measure the cone separation as a function of retinal eccentricity. For all subjects, the measured cone separations agreed well with histological measurements. Furthermore, the contrast of the retinal structures was constant over the 3 degree FOV.
The results indicate that the isoplanatic patch size for the human eye is potentially larger than 1 degree. Widefield imaging has major implications for the clinical applicability of AO as clinicians require the ability to view larger retinal areas than currently provided by existing AO systems.
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