Vitreoretinal surgery is moving towards 3D visualization of the surgical field. This require acquisition system capable of recording such 3D information. We propose a proof of concept imaging system based on a light-field camera where an array of micro-lenses is placed in front of a conventional sensor. With a single snapshot, a stack of images focused at different depth are produced on the fly, which provides enhanced depth perception for the surgeon.
Difficulty in depth localization of features and frequent focus-change during surgery are making current vitreoretinal heads-up surgical imaging systems cumbersome to use. To improve the depth perception and eliminate the need to manually refocus on the instruments during the surgery, we designed and implemented a proof-of-concept ophthalmoscope equipped with a commercial light-field camera. The sensor of our camera is composed of an array of micro-lenses which are projecting an array of overlapped micro-images. We show that with a single light-field snapshot we can digitally refocus between the retina and a tool located in front of the retina or display an extended depth-of-field image where everything is in focus.
The design and system performances of the plenoptic fundus camera are detailed. We will conclude by showing in vivo data recorded with our device.
The resolution of the images obtained from the eye fundus are limited by the ocular aberrations. As most of the aberrations are due to the eye optics, they do not affect the light intensity measured in the eye iris plane. By illuminating the retina with a laser and collecting the light in a pupil plane conjugate, it is possible to apply the imaging correlography technique. From processing series of pupil plane images, this technique gives information about the retina in the form of the squared modulus of the Fourier transform or, equivalently, the autocorrelation of the diffraction-limited image intensity. Two factors make this technique suitable for retinal imaging: 1) For this technique to work, changes of phase distribution in the retinal plane are necessary between each frame. Small eye movements naturally provide these changes; 2) This method does not provide directly the phase of the Fourier transform. Therefore it is of most use for centro-symmetric objects like the retina's photoreceptor mosaic. Preliminary data have been obtained <i>in vivo</i> showing the feasibility of applying such a technique in the eye. Experimental results are compared against simulation based on retinal scattering model.