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B. Lamory, K. Gocho-Nakashima, O. Roche, X. Levecq, F. Harms, J.-L. Dufier; Adaptive Optics Imaging at Large Retinal Eccentricity. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1056.
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© ARVO (1962-2015); The Authors (2016-present)
The study objective was to test the capacity of an adaptive optics (AO) flood illumination fundus camera (FIFC) to image cone photoreceptors at large retinal eccentricities in presence of relatively large off-axis ocular wavefront aberrations (OWA).
The OWA in the right eyes of three young adult subjects were corrected using an AO system operating in closed-loop at 10 Hz, based on a 52-actuator electromagnetic deformable mirror and a 1024 lenslet Shack-Hartmann sensor (both Imagine Eyes, France). A square 3° x 3° area at the eye fundus was flood-illuminated by a pulsed LED emitting at 850 nm and imaged through the deformable mirror at a low-noise CCD camera (Roper Scientific, USA). Retinal images were acquired at 7 different eccentricities ranging between 2° and 45° nasal from the fovea while monitoring the residual wavefront error (RWE). Each acquisition consisted in 20 consecutive images, out of which 10 were numerically averaged to produce an enhanced final image.
The total amount of OWA was found to strongly increase with retinal eccentricity. The root-mean-square (RMS) OWA of the tested eyes was 1,3 µm on average at the center of the fovea and raised up to 4.0µm in average at 45° of eccentricity. The RWE after correction slightly raised with eccentricity, from 0,14µm RMS on average at the center up to 0.3µm at the extreme periphery. As expected, the resulting images showed a variation in the cone density, which decreased from 30000 to 6000 cones/mm² when excentricity increased from 2° up to 35° in agreement with existing histological data. Beyond 35°, cones were still visible but their counting was difficult.
Cone photoreceptors could be imaged at large retinal excentricities using an AO FIFC although large amounts of aberrations were present. This capacity may be critical in using AO technology to diagnose several retinal diseases whose symptoms primarily affect the retinal periphery.
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