1 μm wavelength adaptive optics scanning laser ophthalmoscope

Abstract

An adaptive optics scanning laser ophthalmoscope (AOSLO) corrects ocular aberrations to provide clear retinal images in vivo with high lateral resolution. In this study, we developed an AOSLO system with a 1 μm wavelength probe beam. This wavelength band is effective in improving the retinal imaging capability of AO systems. Because of the long wavelength, the AOSLO system has high tolerance to a mechanical deformation of mirror surfaces; further, it is easier to achieve diffraction limit of the system. To visualize individual photoreceptors, parafoveal regions of retinas of two normal subjects were examined using the 1 μm wavelength AOSLO system. Ocular aberrations were measured using a Shack-Hartmann wavefront sensor and an 840 nm superluminescent diode light source as an AO beacon. A magnetic deformable mirror was used for the correction of ocular aberrations. When AO correction was carried out, the residual RMS wavefront error was measured to be less than 0.1 μm. This residual aberration resulted in a lateral resolution of 3.6 μm of the retinal image. Despite the relatively low transform-limited resolution due to the longer wavelength, the AOSLO could successfully be used to visualize individual photoreceptors, flow of blood cells, and nerve fibers. It was found that the developed AOSLO system with a center wavelength of 1 μm can effectively visualize individual photoreceptors.