Abstract
Purpose::
To demonstrate simultaneous optical coherence tomography (OCT) and scanning laser ophthalmoscope (SLO) imaging of the human cone mosaic without the need of adaptive optics with high speed.
Methods::
The developed system is based on a transversal scanning time domain OCT setup. A resonant scanner working at a frequency of 4kHz was implemented to achieve a high transverse line rate of 8kHz which resulted in a frame rate of 40 fps. The instrument is capable to record OCT B-scans, C (en-face)-scans and 3D data sets with high lateral resolution and a lateral extension of ~1°. Part of the light returning from the retina was directed to an additional detection channel which enabled a simultaneous recording of SLO images. A dynamic focus was incorporated into the system to maintain the high transverse resolution within OCT B-scans and 3D data sets.
Results::
At an eccentricity of ~4° nasally to the fovea the cone mosaic could be resolved in volunteers with good visual acuity. In the OCT B-scans an almost identical regularly spaced structure can be observed within two strong backscattering layers anterior to the RPE which we associated with the interface between inner and outer segments of the photoreceptors (IS/OS) and photoreceptors end tips (PET). The OCT en-face images at the level of the IS/OS show the same cone mosaic as observed with the SLO channel.
Conclusions::
With the proposed system cone mosaic imaging can be achieved without the need of adaptive optics with high speed. One advantage of transversal scanning time domain OCT compared to Fourier- (or Spectral- )Domain OCT besides the possibility to record simultaneously SLO images is the maintenance of high transverse resolution over the whole imaging depth. The higher transverse imaging speed greatly reduced motion artifacts.
Keywords: retina • photoreceptors • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)