Abstract
Purpose: :
To develop an adaptive optics scanning laser ophthalmoscope (AOSLO) that uses a supercontinuum laser and a custom built avalanche photodiodes (APD) with enhanced near-infrared (IR) spectral responsivity, and to apply this instrument to study the spectroscopic reflectance of the cone photoreceptors.
Methods: :
A quasi continuous wave (CW) single mode supercontinuum laser (NKT Photonics A/S, Denmark) that provides light over a spectral range of 500 - 2400 nm was employed as the light source for the AOSLO. A programmable dual-channel acousto-optical tunable filter (AOTF) was used to either continuously tune a single wavelength or simultaneously select multiple wavelengths over the spectral range of 500-1100 nm. The light was fed into the AOSLO through ultra-broadband single mode crystal fibers. A custom APD module with 20 MHz bandwidth, enhanced responsivity in the near-IR region and 4 mm2 active area was developed for photon detection.
Results: :
Through the AOTF, crystal fiber and AOSLO optics, the broadband light source was able to deliver light with adequate power at any specific wavelength over 500 - 1100 nm to the eye, thus, allowing the retina to be imaged with high quality. The new APD detector presented robust spectral response over the spectral range 500 - 1060 nm; in particular, at 1060 nm, the APD demonstrated superior performance compared with other photodetector options. We have obtained high-resolution spectral retinal images in a living macaque eye.
Conclusions: :
The AOSLO, with only one broadband light source and a custom-made APD detector, was able to acquire a full range of spectral retinal images in the living eye. In-vivo study of the spectral reflectance of the photoreceptors and other retinal structures is underway.
Keywords: imaging/image analysis: non-clinical • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • photoreceptors