Abstract
Purpose :
To investigate the feasibility of swept source OCTA (SS-OCTA) imaging of choriocapillaris with a high lateral resolution without adaptive optics
Methods :
A home-built SS-OCTA engine running at 200 kHz A-line rate with a central wavelength of 1060 nm was utilized in our study. A large bean diameter (~3.5mm) was achieved by using a scan lens of 54 mm focal length and an ophthalmic lens of 58 mm focal length with a collimated beam of 3.3 mm in diameter. The resulted lateral resolution is ~ 7.0 um measured by the USAF 1951 resolution target with a phantom eye in the air. Several sampling spacings (10um, 7um and 5um) for the scanning pattern of 2x2mm were designed and implemented to investigate the influence of the incident beam diameter on choriocapillaris imaging. The inter capillary distance was measured by using radially averaged power spectrum in young normal subjects. The choriocapillaris layer (~ 15 um thickness slab under Bruch’s membrane) were segmented and projected onto en face view for visualization purpose.
Results :
Twenty young normal subjects were enrolled in the study with a mean age of 31.5±4.5 years old. The choriocapillaris lobular patterns under fovea were clearly observed with the high-resolution configuration. Surprisingly, the larger sampling space (10 um) had minimal impact on the visualization of the lobular patterns of choriocapillaris (Figure 1). The dense sampling provided higher imaging contrast as expected. The average inter-capillary distance in young normal subjects was 23.5±2.1um.
Conclusions :
The choriocapillaris lobular pattern under fovea has been detected and observed in vivo by high resolution SS-OCTA system with a large field of view and without adaptive optics. Dense sampling can improve the imaging contrast of choriocapillaris imaging but with no impact on the measurement of inter capillary distance. The high resolution choriocapillaris imaging may not only play a role in studying the ocular diseases, such as dry and wet AMD, but also is helpful in developing endpoints for therapeutic trials.
This is a 2020 Imaging in the Eye Conference abstract.