Lamina cribrosa (LC) is known to be a putative site of retinal ganglion cell axonal injury. Moreover, there is increasing evidence that morphological changes of the LC including focal LC defect and increased LC curvature may be associated with the impaired optic nerve head (ONH) microvasculature in glaucoma due to the recent advent of optical coherence tomography (OCT-A) that enables visualization of the superficial and deeplayer microvasculature.1-4 Particularly, assessment of the microvasculature within the LC is essential in understanding the direct relationship between the mechanical and vascular changes of the ONH.2-4
OCTA is still an evolving technology and these results highlight the fact that there is a need for consensus on the method that is best suited for quantification
Numa and Akagi et al. nicely demonstrated that Swept source (SS)-OCT angiography system, multiple image averaging, and a projection resolved algorithm enabled enhanced visualization of the microvasculature within the LC. They showed that OCT-A signals are present in lamina beams, not in lamina pores and that glaucomatous eyes had lower signal than normal eyes. Averaging of multiple OCT-A images enhanced the image quality. In addition, the projection removal technique allowed removing artifacts of the superficial vessels thus provided more accurate information of the deep ONH microvasculature.
However, caution is needed in assessing the microvasculature within the LC. Firstly, the current projection removal technique is not perfect. Residual projection of the large vessels is still observed in the enface OCT-A image of this article (Figs. 1G and 2G). On the other hand, the true vasculature located in the prelaminar tissue can be removed. Further enhancement of the analytics for the user-defined artifact removal is required. Secondly, assessment of the LC microvasculature is problematic in a considerable number of eyes due to shadowing by a neuroretinal rim and large retinal vessels. Despite these limitations, this study has its clinical importance by introducing up-todate OCT-A technique in visualizing the LC microvasculature. Ongoing innovation on the OCT-A analytics may help us better understand the pathogenic role of the LC vasculature in the development and progression of glaucoma.