High resolution multimodal clinical ophthalmic imaging system
Spotlight summary: High-resolution in vivo imaging of normal and diseased eyes using adaptive optics and optical coherence tomography has significantly advanced our understanding of retinal structure and function on a microscopic scale. Despite these advances, there is still a strong need to deploy these technologies into the hands of clinicians and research scientists to better explore the mechanisms of retinal disease and potentially allow for their earlier detection and treatment. Optical coherence tomography (OCT), a technology that obtains cross-sectional images with high axial resolution, enjoyed a very rapid transition from the research environment to the clinic. It is currently a well-accepted, standard tool used to image the integrity of different cellular layers in the retina and diagnose and monitor the progression of retinal diseases. Adaptive optics (AO) is a complimentary imaging technology that provides excellent lateral resolution through correction of the eye’s aberrations. While AO has been used in vivo to examine a host of different cell types in normal and diseased eyes (e.g., cone photoreceptors, retinal ganglion cells, retinal pigment epithelial cells, white blood cells), its transition to the clinical arena has been dramatically slower. The narrow field-of-view associated with AO images (typically 1–3 deg) often makes it challenging to pinpoint the specific location being imaged in the retina and requires the user to take several images at adjacent retinal locations to slowly construct a montage of a larger patch of retina (typically done by hand) that can be registered with traditional, wide-field photos. Additionally, the ability to acquire AO images at different locations can be limited by a host of factors, such as the patient’s ability to fixate and the stability of the patient’s eye during image acquisition.
The multimodal imaging instrument presented by Mujat et al. (which combines AO confocal scanning laser ophthalmoscopy with OCT) represents an important first step in developing an AO-based imaging system that can be clinically deployed. While this instrument has been tested only in normal eyes thus far, its images and resolution compare favorably with those acquired in normal eyes using other custom-built AO and OCT systems. The instrument incorporates several modules that make it convenient from a practical acquisition point-of-view. First, the instrument includes a wide-field imaging system (~33 deg) that allows the user to specify and simultaneously view the narrower-field retinal location being imaged with AO or OCT. Secondly, high-resolution images can be acquired at many retinal locations faster and more easily by simply having the patient look straight ahead while the imaging beam is slowly steered across the desired patch of retina (as opposed to traditional systems that have a stationary imaging beam and rely on the patient’s ability to fixate at different retinal locations—a potentially challenging task for patients with retinal disease). Additionally, the effect of eye movements on the generation of high-resolution registered images can be reduced by use of a retinal tracker that can stabilize eye movements with an accuracy on the order of micrometers. Finally, this multimodal instrument can simultaneously acquire en face AO and cross-sectional OCT images at the same retinal location, mitigating the challenges associated with attempting to acquire and coregister AO and OCT images taken separately in time at the exact same retinal location.
Neither AO nor OCT imaging can be used on their own to provide a complete understanding of retinal function and/or structure in the living eye. While the combination of AO with confocal scanning laser ophthalmoscopy and OCT imaging is not novel to this work, the authors of this paper have developed an instrument with several convenient and user-friendly modules that could accelerate the application of these technologies to the clinical environment. It remains to be seen whether AO imaging will become as routinely adopted as OCT in the clinical community. However, instruments such as the one in this paper will enable us to assess the potential for making new discoveries in the origins and management of retinal disease, as well as their treatment, in the clinic.
Technical Division: Vision and Color
ToC Category: Vision, Color, and Visual Optics
|OCIS Codes:||(170.0110) Medical optics and biotechnology : Imaging systems|
|(170.4470) Medical optics and biotechnology : Ophthalmology|
|(170.5755) Medical optics and biotechnology : Retina scanning|
|(110.1080) Imaging systems : Active or adaptive optics|
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