To the Editor:
Posterior vitreous structures are visualized using conventional enhanced vitreous imaging modality of spectral domain optic coherence tomography (EVI SD-OCT) [1] and swept-source OCT (SS-OCT) [2]. SS-OCT can clearly show posterior precortical vitreous pockets (PPVP), the primary pathogenic event in idiopathic macular hole formation [3].
Here, we introduce a modified EVI SD-OCT (mEVI-OCT) based on Spectralis OCT2 (Heidelberg Engineering, Heidelberg, Germany). This novel simple modification combines vitreous and choroidal images with retinal image into one image.
The mEVI-OCT images were obtained under high resolution with a 55° or 30° raster. A 55° raster increases the field depth better than a 30° raster. The retinal layers are positioned in the lower third of an image to obtain an imaging depth that penetrates into the vitreous. Scans are obtained by switching from focusing on the retina to the vitreous by turning the dial slowly, about 1.0–2.0 diopters counterclockwise while scanning. After 75% of the frames have been completed, the enhanced depth imaging (EDI) function is activated to finish the remaining 25%. The mEVI-OCT images are developed after maximizing the contrast in the images to visualize the posterior vitreous, retina, and choroid in detail, including the premacular bursa or PPVP, Cloquet’s canal, prevascular vitreous fissures, cisterns, and choroidal–scleral interface (Figs. 1 and 2), which were not inferior to SS-OCT previously [2, 4].
A possible mechanism of mEVI-OCT is that for 75% of the frames, the zero-delay line is displaced into the vitreous, resulting in vitreous imaging with high resolution. The EDI function guarantees that the deep choroid visualization is less susceptible to sensitivity roll-off [5], completing the remaining 25% frames.
Compared with the conventional EVI mode [1], mEVI-OCT has a larger field depth because of the 55° raster and can better visualize deep choroids owing to its EDI function in the last 25% of the frames. Unlike the long wavelength in SS-OCT [2,3,4], the mEVI-OCT signal is less attenuated by the fluid in the anterior chamber and vitreous and has a higher inherent axial resolution. Although we could not compare between SS-OCT and mEVI-OCT in the same patient, mEVI-OCT is still promising based on our current data.
References
Takahashi A, Nagaoka T, Yoshida A. Enhanced vitreous imaging optical coherence tomography in primary macular holes. Int Ophthalmol. 2016;36:355–63.
Barteselli G, Bartsch DU, Weinreb RN, Camacho N, Nezgoda JT, Marvasti AH, et al. Real-time full-depth visualization of posterior ocular structures: comparison between full-depth imaging spectral domain optical coherence tomography and swept-source optical coherence tomography. Retina. 2016;36:1153–61.
Lavinsky F, Lavinsky D. Novel perspectives on swept-source optical coherence tomography. Int J Retin Vitreous. 2016;2:25.
Gal-Or O, Ghadiali Q, Dolz-Marco R, Engelbert M. In vivo imaging of the fibrillar architecture of the posterior vitreous and its relationship to the premacular bursa, Cloquet’s canal, prevascular vitreous fissures, and cisterns. Graefes Arch Clin Exp Ophthalmol. 2019;257:709–14.
Spaide RF, Koizumi H, Pozzoni MC. Enhanced depth imaging spectral-domain optical coherence tomography. Am J Ophthalmol. 2008;146:496–500.
Funding
This study was funded by the Fund for Scientific Research of The First Hospital of China Medical University (No.FSFH201712), Clinical Genetics (Ophthalmology) Subject construction project of China Medical University (No. 3110118049), and Natural Science Foundation of Liaoning Province (No. 20170541041).
Author information
Authors and Affiliations
Corresponding author
Ethics declarations
Conflict of interest
The authors declare that they have no conflict of interest.
Additional information
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
About this article
Cite this article
Hua, R., Ning, H. Modified enhanced vitreous imaging modality of spectral domain optic coherence tomography. Eye 35, 351–352 (2021). https://doi.org/10.1038/s41433-020-0814-3
Received:
Revised:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1038/s41433-020-0814-3