Combinations of techniques in imaging the retina with high resolution

Developments in optical coherence tomography (OCT) have expanded its clinical applications for high-resolution imaging of the retina, as a standalone diagnostic and in combination with other optical imaging modalities. This review presents currently explored combinations of OCT technology with a variety of complementary imaging modalities along with augmentational technologies such as adaptive optics (AO) and tracking. Some emphasis is on the combination of OCT technology with scanning laser ophthalmoscopy (SLO) as well as on using OCT to produce an SLO-like image. Different OCT modalities such as time domain and spectral domain are discussed in terms of their performance and suitability for imaging the retina. Each modality admits several implementations, such as flying spot or using an area or line illumination. Flying spot has taken two principle forms, en-face and longitudinal OCT. The review presents the advantages and disadvantages of different possible combinations of OCT and SLO with AO, evaluating criteria in choosing the best OCT method to fit a specific combination of techniques. Some of these combinations of techniques evolved from bench systems into the clinic, their merit can be judged on images showing different pathologies of the retina. Other potential combinations of techniques are still in their infancy, in which case the discussion will be limited to their technical principles. The potential of any combined implementation to provide clinical relevant data is described by three parameters, which take into account the number of voxels acquired in unit time, the minimum time required to produce or infer an en-face OCT image (or an SLO-like image) and the number of different types of information provided. The current clinically used technologies as well as those under research are comparatively evaluated based on these three parameters. As the technology has matured over the years, their evolution is discussed as well with their potential for further improvements.