Purpose:
Choroidal abnormality recently attracts ophthalmologists’ interest. To visualize the choroid, two modalities of optical coherence tomography (OCT) are emerging: high-penetration (HP-) OCT using 1 um wavelength light and enhanced depth imaging (EDI). This study aims at demonstrating super penetration imaging of choroid by the combination of HP-OCT and EDI.
Methods:
10 eyes of 5 normal subjects and 16 eyes of 10 cases including 7 polypoidal choroidal vasculopathy, 2 age-related macular degeneration and 1 central serous chorioretinopathy were involved. 10 normal and 10 pathologic eyes were scanned by a custom-built HP-OCT based on swept-source OCT technology and a 830 nm spectral domain (SD-) OCT (Spectralis). 6 pathologic eyes were scanned by high-resolution (HR-) HP-OCT based on SD-OCT technology. HP-OCTs use a probe wavelength around 1.05 um, and have depth resolutions of 10 um (HPOCT) and 4.3 um (HR-HPOCT) in tissue. Two types of EDI images were created by the averaging of 10 (EDI10) and 50 (EDI50) frames. The visibility of chorio-scleral interface (CSI) was examined by a grader with 3-level score: 0 invisible to 2 clearly visible. The visibility of structures in sclera was also examined.
Results:
EDI10 as well as EDI50 images of HPOCT were comparable and revealed fine details of the pathologies even beneath hyper-scattering objects as shown in the figure. Both EDI10 and EDI50 images provide better mean visibilities of CSI with HP-OCTs than Spectralis. For pathologic eyes, these were 1.25 to 1.7 (EDI10, Spectralis to HP-OCTs (SH)), 1.5 to 2.0 (EDI50, SH). For normal eyes, these were 1.5 to 1.9 (EDI10, SH), and 1.8 to 2.0 (EDI50, SH). The scleral visibility was 0.0 to 0.7 (EDI10, SH, p=0.01) and to 0.5 to 1.1 (EDI50, SH).
Conclusions:
The combination of HP-OCT and EDI provided the detailed visualization of choroid and sclera. The fine details of the deep pathologies can be visualized by this combination.
Keywords: choroid • age-related macular degeneration • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)