Abstract
Purpose: :
Retinal imaging methods that allow enhanced visualization and quantification of alterations in the retinal structures and vasculatures are essential to improve the evaluation of retinal diseases and provide knowledge on their pathophysiology. A prototype optical imaging system based on the RTA technique was developed for generating three–dimensional images of the retinal tissue in living eyes.
Methods: :
A laser beam was projected at an oblique angle on the retina to generate an optical section image in the YZ plane of the retina. Since the incident laser beam was not coaxial with the viewing system, structures at various retinal depths appeared laterally displaced according to their depth location on the optical section image. The laser beam was scanned to acquire a series 40 optical section images, each spatially separated by 25 microns on the retina. An automated software algorithm was developed that segmented the optical section images and combined the segments from the same retinal depth. This process was repeated for each layer to construct a set of en face retinal images in the XY plane, parallel to the retinal surface and displaced in depth. Imaging was performed in 5 healthy human subjects and 5 patients with diabetic retinopathy.
Results: :
A set of 8 depth–displaced en face images of retinal layers was constructed in each eye that encompassed a 1.0 mm by 1.5 mm retinal area. The retinal imaging areas were determined by an internal fixation target. On the en face retinal images, the foveal depression and the surrounding retinal vasculatures were delineated. En face retinal images had higher contrast as compared to images obtained by a clinical fundus camera and allowed enhanced visualization of the retinal structures and vasculatures.
Conclusions: :
An optical system for three–dimensional retinal imaging is reported that has potential as a promising tool for evaluation of retinal pathologies associated with chorioretinal diseases.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)