Study Of Retinal Dark Field Imaging Technique

About80%of all the information people get from the outside reality is by eyes.The number of people with eye diseases is quite large, and seems to be still rising.Most eyes lesions actually arise from the retina. In addition, medical research hasproved that diabetes and other diseases can be reflected in the fundusmicrocirculation. Therefore, fundus imaging with high contrast and high resolutiontechnology are of great value in medical research and clinical application.Introducing adaptive optics technology into retinal imaging has solved theproblem of high resolution imaging of the retina. However, through the preliminaryclinical trials, it is found that, with the high resolution imaging techniques nowavailable, we could only distinguish the photoreceptor cell layer, capillary vessellayer and nerve fiber layer structure out of the10-layerretina, and cannot distinguishthe other layers. This is because the human retinal cells are small ones with highlight transmission and differences between the refraction indexes of other layers arerelatively small, making the retina a kind of low contrast objects. We must achieveboth high resolution and high contrast imaging to effectively distinguish the retina.Dark field imaging technique has been applied in in-vivo retinal imaging to improveimage contrast, which is a new direction in retinal imaging.In this paper, from the meaning of retinal dark field imaging, we introduce itsadvantage and research progress at home and abroad. The optical system of thehuman eye and the retinal structure is also presented. The basic principle of darkfield imaging is outlined and its mathematical model is given. Then the influence ofwavefront aberrations on contrast dark field imaging technology is analyzedqualitatively in theory. Finally, based on the statistical aberration data of normal eyes,the effect of residual aberration on dark field imaging contrast is simulated andquantitatively analyzed. Based on the37unit in-vivo retinal imaging apparatus, thedark field imaging experiment is carried out. Firstly, we put forward three kinds of dark field imaging scheme and analyses its limitation and the difficulties oftechnology, and accordingly determine final experimental scheme. Then takingartificial eye as an example, we give the experimental results of dark field imaging.Through comparison with conventional imaging results, we conclude that our darkfield imaging experiment scheme can effectively improve image contrast. Finally,through the introduction of defocus in the experiment, the simulation analysis isverified toughly.