Measuring optic nerve head perfusion to monitor glaucoma: a study on structure–function relationships using laser speckle flowgraphy

Abstract

Purpose We aimed to describe the global and localized correlations among visual field (VF) sensitivity, optic nerve head (ONH) perfusion measured by laser speckle flowgraphy (LSFG) and neural structure measured by optical coherence tomography (OCT) in open‐angle glaucoma (OAG) and to compare the floor effect for LSFG and OCT. Methods Cross‐sectional, multicenter study including one eye each from fifty OAG patients (mean age 69.3 years; average VF mean deviation, MD, −8.5 dB, range −25.17 to 0.85 dB) and fifty‐one controls. Patients underwent SITA standard 24‐2 automated perimetry and measurement of ONH perfusion, peripapillary retinal nerve fibre layer thickness (RNFLT) and macular ganglion cell‐inner plexiform layer thickness (GCIPLT). We tested the presence of a significant change (breakpoint) in the correlation slope with VF sensitivity to assess floor effect. Results The correlation between the LSFG parameter Mean All (MA) of the global disc area and MD (r = 0.56, p < 0.001) did not show a breakpoint, in contrast to the correlations between MD and OCT global parameters, which showed breakpoints at −8.53 and −4.05 dB for RNFLT and GCIPLT, respectively. Global and localized correlations with VF sensitivity were stronger for LSFG compared to OCT. In particular, LSFG outperformed OCT in the correlation with the central VF sector (r = 0.50, p < 0.001 and r = 0.06, p = 0.67 for MA and RNFLT, respectively). Conclusion The global and sectoral correlations with VF sensitivity and the favourable floor effect compared to OCT indicate LSFG as a promising tool to monitor progression particularly in late‐stage glaucoma. Further longitudinal studies are warranted.

Combining OCT and OCTA for Focal Structure–Function Modeling in Early Primary Open-Angle Glaucoma

“… 12 In glaucoma, the usefulness of OCTA-based vascular metrics has been demonstrated in the discrimination of diseased eyes from healthy eyes. 13 – 15 Relating structural and, increasingly, vascular 16 – 25 changes with functional loss of vision in glaucoma is referred to as the structure–function relationship. 26 – 28 …”

Evaluation of Microcirculation in Optic Nerve Head Using Laser Speckle Flowgraphy in Active Thyroid Eye Disease

“…Using ANOVA, we found that MBR-overall, MBR-vessel, and MBR-tissue were lower in eyes with more severe active TED. The MBR can quantitatively measure blood flow velocity of the ONH in LSFG examinations ( 14 , 15 ). Lower MBRs may indicate slower ONH blood flow velocities in patients with more severe active TED.…”

“…Laser speckle flowgraphy (LSFG) is based on the laser speckle phenomenon and is a noninvasive instrument that can measure two-dimensional relative blood flow velocity of the ocular microcirculation in real time ( 12 , 13 ). The mean blur rate (MBR), which represents the velocity of optic nerve blood flow, has been previously applied to monitor the severity of glaucoma ( 14 , 15 ), evaluate ischemic optic neuropathy ( 16 , 17 ), and detect retinal diseases ( 18 ). Although LSFG can be used to estimate optic nerve blood flow, to the best of our knowledge, it has never been used to monitor blood flow changes in patients with TED or to evaluate the severity of TED.…”

Longitudinal Study of Optic Disk Perfusion and Retinal Structure in Leber's Hereditary Optic Neuropathy

“…An elliptical region of interest (ROI) was drawn in a semi-automated fashion to fit the ONH borders, having as a reference the color fundus photograph, as previously described. 25 Within each ROI, the mean perfusion in the ONH microvasculature (referred to as Mean Tissue [MT]) was calculated using the “Cross-section” automated segmentation tool of the software. The mean of two scans was then averaged.…”