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Editors Selection IGR 16-1

Clinical Examination Methods: Measuring ONH perfusion

Comment by Yoshiaki Yasuno on:

56439 Optical Coherence Tomography Angiography of Optic Disc Perfusion in Glaucoma, Jia Y; Wei E; Wang X et al., Ophthalmology, 2014; 121: 1322-1332

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The authors developed and applied a new angiographic modality, optical coherence tomography angiography (OCTA), to glaucoma subjects including eight perimetric glaucoma and three pre-perimetric glaucoma subjects together with 24 normal controls. The OCTA is an emerging modality enabling non-invasive angiography of posterior eye. Among several variations of OCTA, the authors utilized their own developed method, split-spectrum amplitude-decorrelation angiography (SSADA), which is minimally suffered by subject motion and provides high contrast en-face and three-dimensional angiographies of a macula and an optic nerve head. The authors first utilized OCTA for quantitative observation of vasculature at the optic nerve head. This observation showed that the normal discs had denser microvascular network than glaucomatous discs. In addition, there appeared to be reduced flow in the lamina region of the glaucomatous disc compared with the normal disc.

OCTA may become a powerful tool for glaucoma diagnosis and evaluation of glaucoma progression

Although OCTA was originally utilized for qualitative imaging of vasculature, the authors also developed a quantitative metric based on OCTA, so called as a disc flow index, which is expected to be large if the flow is large. The flow index showed high intra-visit repeatability (1.2%) and inter-visit reproducibility (4.2%). The disc flow index in the glaucoma group was 25% lower than the normal group (p = 0.003). The disc flow index was significantly negatively correlated with visual field pattern standard deviation in the glaucoma group (R² = 0.752, p = 0.001). This suggests that the flow index may be a good indicator of glaucoma severity. This study has shown that OCTA is useful for both qualitative angiographic observation of optic disc as well as quantitative evaluation of the flow in the optic disc. OCTA may become a powerful tool for glaucoma diagnosis and evaluation of glaucoma progression.

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