Abstract
Abstract: :
Purpose: Adaptive optics (AO) technology enables to image the retina at a level of high magnification, in which photoreceptors might be visible in vivo, by canceling ocular wavefront aberration. We examined the fundus of normal volunteers and a patient using a prototype adaptive optics fundus camera. Methods: Prototype adaptive optics fundus camera (Topcon corp. Tokyo, Japan) was used under the approval of the IRB of Osaka University Medical School. The device incorporates a 635nm luminescence diode illuminator, and 768 x 768 pixel refractive liquid crystal light modulator (Hamamatsu photonics, Hamamatsu, Japan), in which wavefront aberration is reduced up to 8th order. The liquid crystal device corrects wavefront aberration on time at 3Hz response rate. Fundus image was taken when RMS error was reduced below 0.10 um. Seven normal eyes (6 male, 1 female, 33.3 ±6.5y.o.; Mean±SD) and one patient with cone dystrophy (male, 43 y.o.) were imaged under pupil dilation. Results: In normal dilated eyes, the device improved the strehl ratio from 0.028±0.006 (AO off) to 0.612±0.079 (AO on), as well as ocular RMS from 0.552±0.068 um (AO off) to 0.076±0.008 um (AO on) at 6mm pupil. Fundus images were sampled at the parafoveal area approximately 3 degrees from the fovea by off–axis fixation. Mosaic structure, consisted with approximately 2–3 um diameter compartments, was visualized in all normal eyes. This was consistent with previous reports in which photoreceptors were imaged in vivo using an adaptive optics device. In a cone dystrophy patient, the mosaic structure was less distinctive and some dotted smaller compartment structures were observed, instead. Conclusions: The adaptive optics fundus camera could visualize retinal image at a photoreceptor level. This device has a potential to study live photoreceptor change in retinal disorders, and further to be used for a diagnosis by examining photoreceptor arrangement. Further improvement of image processing software as well as device structure must be necessary.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • photoreceptors • retina