Abstract
Purpose :
Adaptive optics (AO) allows high resolution imaging of the retina. It has been successfully applied to numerous ophthalmology instruments (fundus camera, scanning laser ophthalmoscope, optical coherence tomography, etc.). One limit of this technique is the small field of view (FoV) on which the correction can be efficiently applied. Indeed, the isoplanatic patch size of the eye and the optical design of the instruments induce a degradation of the image quality while increasing the FoV. We performed an exploratory study tackling this issue: new concepts of adaptive optics scanning laser ophthalmoscope (AO-SLO) were theoretically and experimentally analysed.
Methods :
The study consisted of 3 steps. Firstly, in-vivo measurements of the eyes of 3 healthy volunteers were performed on a lens-based AO-SLO set-up. The aberrations of the eyes were measured for different fixation angles to characterize the isoplanatic patch and assess the AO correction performance with a larger FoV. Secondly, optical ray tracing was used to model the AO-SLO set-up and its correction performance. Different options were explored to increase the performance over a large FoV: optical design, number and position of deformable mirror, number of wave-front sensor and control strategy. Thirdly, a new instrument arising from the modelling step was integrated and characterized under the same conditions than in the first step, in order to validate its benefit for larger FoV imaging.
Results :
Firstly, the isoplanatic patch of the 6 measured eyes was found around 1°, which is in accordance with the literature and our modelling. Secondly, a new design was developed to enlarge the FoV. It consists of the classical AO-SLO lens based set-up, with one additional deformable mirror to correct for the aberrations varying in the FoV. Moreover, the adopted control strategy allows using only one wavefront sensor. With this concept and a representative eye model, diffraction limited performance is obtained over a 5° FoV at the entrance of the eye. Thirdly, the results of the model were validated in-vivo with the 3 volunteers.
Conclusions :
A new concept for enlarging the FoV in AO-SLO was developed. The use of a second deformable mirror and an optimized optical design allow high resolution imaging over a 5° scanning angle on the eye.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.