Visualization of Human Photoreceptors Using 1 µm Wavelength Adaptive Optics Scanning Laser Ophthalmoscope

Abstract

Purpose: : Adaptive optics scanning laser ophthalmoscope (AOSLO) provides beautiful retinal images with high lateral resolution. On the other hand, one-micrometer wavelength is an emerging interesting wavelength band to improve the retinal imaging capability. This paper aims at demonstrating the visualization of photoreceptors by 1 µm AOSLO.

Methods: : A custom 1 µm AOSLO was built by authors. A Shack-Hartmann wavefront sensor (Haso32, Imagine eyes), a 840 nm beacon beam, and a magnetic deformable mirror (Mirao52, Imagine eyes) were used to measure and cancel ocular aberrations. The AOSLO uses a probe beam with a 1040 nm center wavelength. Since a local minimum of water absorption and dispersion is located at around 1 µm, a low chromatic aberration is expected. Further, the longer wavelength has a larger tolerance to the mechanical deformation of mirror surface, and it is easier to achieve diffraction limit. The residual RMS wavefront error was measured to be less than 0.1 µm when AO is on. This provides the lateral resolution of 3.6 µm on the retina. Four eyes of 4 normal subjects were involved in this study.

Results: : The individual photoreceptors at parafoveal region were clearly visualized for all subjects as shown in the figure. The superficial layer’s micro structures, such as the blood capillaries and the flow of blood cells, were also observed.

Conclusions: : It was found that the new wavelength of 1 µm has the capability to visualize individual photoreceptors.

Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • imaging/image analysis: non-clinical • photoreceptors