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Editors Selection IGR 19-4

Clinical Examination Methods: Pulsatile Trabecular Motion and IOP Fluctuations

Comment by Clemens Strohmaier & Alex Huang on:

100738 Pulsatile Trabecular Meshwork Motion: An Indicator of Intraocular Pressure Control in Primary Open-Angle Glaucoma, Du R; Xin C; Xu J et al., Journal of clinical medicine, 2022; 11:

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This cross-sectional study by Du et al. used phase-sensitive OCT to assess pulsatile trabecular meshwork motion (TM) in glaucomatous eyes compared to healthy individuals. Their main finding is reduced motion (maximum velocity and cumulative displacement) in glaucoma subjects compared to controls. Within the glaucoma group, they reported reduced motion in individuals with high IOP fluctuations ('fluctuant', 9.9 mmHg diurnal amplitude) compared to those with lower fluctuations ('stable', 4.0 mmHg diurnal amplitude). Furthermore, regional differences between the quadrants of individual eyes have been found, with the nasal area showing increased motion compared to temporal. This was seen in healthy individuals as well as glaucomatous eyes.

An important assessment for any new method is reliability and reproducibility, and the authors showed excellent results for their velocity and motion measures.

However, it is unclear if this only included normal subjects. Imaging disease is often more difficult. Since the TM impacts IOP, IOP varies through the day, IOP behavior changes in glaucoma, and because the authors specifically compare IOP stable and IOP fluctuant subjects, very high reliability and reproducibility in glaucoma eyes might not be expected.

Nevertheless, the study is interesting in many aspects: it demonstrates the clinical applicability of a non-invasive tool to assess the biomechanical properties of the trabecular meshwork. Furthermore, it shows differences in these biomechanical properties between healthy individuals and patients with glaucoma. Lastly, it highlights the regional differences within the quadrants of each individual eye.

Overall, this study adds further evidence that the reduction of outflow facility to a single number ‐ as modelled by the Goldmann equation ‐ is not a precise characterization of aqueous humor outflow anymore. Instead, we need to consider the spatial differences within the eye, develop novel models and tools to assess biological properties adequately and lastly treat aqueous humor outflow as a dynamic system with changes over time.

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