Conventional scanning laser ophthalmoscopy (SLO) utilizes a finite collection pinhole at a retinal conjugate plane to strongly reject out-of-focus light while primarily transmitting the in-focus, retinal backscattered signal. However, to improve lateral resolution, a sub-Airy disk collection pinhole is necessary, which drastically reduces the signal-to-noise ratio (SNR) of the system and is thus not commonly employed. Recently, an all-optical, super-resolution microscopy technique known as optical photon reassignment (OPRA) microscopy (also known as re-scan confocal microscopy) has been developed to bypass this fundamental tradeoff between resolution and SNR in confocal microscopy. We present a methodology and system design for obtaining super resolution in retinal imaging by combining the concepts of SLO and OPRA microscopy. The resolution improvement of the system was quantified using a 1951 USAF target at a telecentric intermediate image plane. Retinal images from human volunteers were acquired with this system both with and without using the OPRA technique to demonstrate the resolution improvement when imaging parafoveal cone photoreceptors. Finally, we quantified the resolution improvement in the retina by analyzing the radially averaged power spectrum of the retinal images.
Francesco LaRocca, Theodore B. DuBose, Sina Farsiu, and Joseph A. Izatt, "Optical photon reassignment super-resolved scanning laser ophthalmoscopy (Conference Presentation)," Proc. SPIE 10045, Ophthalmic Technologies XXVII, 100451C (Presented at SPIE BiOS: January 29, 2017; Published: 16 May 2017); https://doi.org/10.1117/12.2252384.5370275065001.
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