Evaluation of optic nerve head blood flow in response to increase of intraocular pressure

Iwase, Takeshi; Akahori, Tomohiko; Yamamoto, Kentaro; Ra, Eimei; Terasaki, Hiroko

doi:10.1038/s41598-018-35683-y

Cited by 19 publications

(18 citation statements)

References 42 publications

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“…Because the OPT is easier to perform and is better tolerated than the standard tonography techniques, it has been widely adopted in recent years. 15 – 19 …”

Section: Discussionmentioning

confidence: 99%

Acute Effects of Intraocular Pressure-Induced Changes in Schlemm's Canal Morphology on Outflow Facility in Healthy Human Eyes

Chen

et al. 2020

Invest. Ophthalmol. Vis. Sci.

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Purpose To estimate the outflow facility coefficient (C) as a function of Schlemm's canal cross-sectional area (SCAR) in healthy subjects using noninvasive oculopression tonometry (OPT). Methods In 25 healthy volunteers, intraocular pressure (IOP) decay values were recorded by a ophthalmodynamometer, with a fixed external force (0.15 N) on the inferior-temporal eyelid, every 10 seconds, for four minutes, and again after a 30-minute rest. Schlemm's canal profile images and IOP were obtained pre-procedurally (baseline), immediately (T0), and at 1-minute intervals post-procedurally (T1, T2, T3, and T4). C was calculated for different IOPs. The SCAR, coronal, and the meridional diameter of Schlemm's canal were calculated. Results Mean C 0 for the maximum IOP was 0.020 ± 0.017 µL/min/mm Hg; mean C was 0.018 ± 0.0071 and 0.058 ± 0.0146 µL/min/mm Hg at 40 and 20 mm Hg, respectively. C was nonlinearly dependent on the IOP ( R 2 = 0.945). The SCAR was 5440 ± 3140.82, 3947.6 ± 2246.8, and 5375.7 ± 2662.7 µm 2 at baseline, T0, and T4, respectively. The coronal diameter of SC decreased significantly from the baseline (33.02 ± 11.3 µm) to T0 (26.6 ± 9.37 µm) and recovered at T4 (32.3 ± 9.53 µm). The SCAR and IOP correlated significantly throughout ( R 2 = 0.9944; P < 0.001). C0 significantly correlated with the SCAR at baseline and with changes in the SCAR and IOP from T0 to T4. Conclusions Schlemm's canal dimensions are responsible for the IOP-dependent mechanical forces, and these changes appear to directly affect outflow facility.

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“…Because the OPT is easier to perform and is better tolerated than the standard tonography techniques, it has been widely adopted in recent years. 15 – 19 …”

Section: Discussionmentioning

confidence: 99%

Acute Effects of Intraocular Pressure-Induced Changes in Schlemm's Canal Morphology on Outflow Facility in Healthy Human Eyes

Chen

et al. 2020

Invest. Ophthalmol. Vis. Sci.

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“…We evaluated the pulse waveforms using a linear mixed model to incorporate possible correlations between repeated measured values of the parameters for each eye over time within a subject, which was the same statistical method as previously reported [ 1 , 2 ]. Briefly, we assumed the following model,…”

Section: Methodsmentioning

confidence: 99%

“…Recently, a study by Popa-Cherecheanu et al has investigated the regulation of ocular blood flow under artificial continuous IOP elevation using a suction cup and laser Doppler flowmetry [ 16 ]. Earlier, a testing protocol was also established to examine the response of blood flow on the ONH induced by changes in the OPP induced by an artificial elevation of the IOP, and the elevated IOP was found to be stable and reproducible [ 1 , 2 ].…”

Section: Introductionmentioning

confidence: 99%

Changes in pulse waveforms in response to intraocular pressure elevation determined by laser speckle flowgraphy in healthy subjects

Iwase

Tomita

et al. 2021

BMC Ophthalmol

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Background The influences of intraocular pressure (IOP) elevations on the pulse waveform in the optic nerve head (ONH) were evaluated using laser speckle flowgraphy (LSFG) in normal subjects. Methods This prospective cross-sectional study was conducted at the Nagoya University Hospital. An ophthalmodynamometer was pressed on the sclera to increase the IOP by 20 mmHg or 30 mmHg for 1 min (experiment 1, 16 subjects) and by 30 mmHg for 10 min (experiment 2, 10 subjects). The mean blur rate (MBR) and the eight pulse waveform parameters determined using LSFG were measured before, immediately after and during an IOP elevation, and after the IOP returned to the baseline pressure. Results A significant elevation in the IOP and a significant reduction in the ocular perfusion pressure (OPP) were found after applying the ophthalmodynamometer (both, P < 0.001). The blowout score (BOS) reduced significantly (P < 0.001), and the flow acceleration index (FAI; P < 0.01) and resistivity index (RI; P < 0.001) increased significantly immediately after increasing the IOP by 20 or 30 mmHg (experiment 1). The BOS reduced significantly (P < 0.001), and the FAI (P < 0.01) and RI (P < 0.001) increased significantly after the IOP elevation by 30 mmHg in both experiment 2 and 1. However, the BOS and RI recovered significantly at time 10 compared to that in time 0 (immediately after IOP elevation) during the 10-min IOP elevation (P < 0.001 and P = 0.008, respectively). Conclusions In conclusion, the BOS, FAI, and RI of the pulse waveforms changed significantly with an acute elevation in the IOP. The change should be related to the larger difference between the maximum and minimum MBRs during the IOP elevation.

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“…Earlier, we established a testing protocol that was used to examine the response of blood ow on the ONH induced by changes in the OPP induced by an arti cial elevation of the IOP [15,16]. This method elevated the IOP continuously by applying pressure on the eye with an ophthalmodynamometer, and we found that it was a stable and reproducible.…”

Section: Introductionmentioning

confidence: 94%

“…We evaluated the pulse waveforms using a linear mixed model to incorporate possible correlations between repeated measured values of the parameters for each eye over time within a subject, which was the same statistical method as previously reported [15] [16]. Brie y, we assumed the following model, y ij = a i + f(tj:b) + ε i j i (subject) = 1, ….…”

Section: Statistical Analysesmentioning

confidence: 99%

Changes in Pulse Waveforms in Response to Intraocular Pressure Elevation Determined by Laser Speckle Flowgraphy in Healthy Subjects

Iwase

Tomita

et al. 2021

Preprint

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Background: To determine whether autoregulation of the blood flow is present in the blood flow on the optic nerve head (ONH) by intraocular pressure (IOP) elevations using pulse waveform parameters determined by laser speckle flowgraphy (LSFG) in normal subjects.Methods: We conducted this prospective cross sectional study at the Nagoya University Hospital. An ophthalmodynamometer was pressed on the sclera to increase the IOP by 20 mmHg or 30 mmHg for 1 min (Experiment 1, 16 subjects) and by 30 mmHg for 10 min (Experiment 2, 10 subjects). The mean blur rate (MBR) and the eight pulse waveform parameters determined by LSFG were measured before, immediately after and during an IOP elevation, and after the IOP returned to the baseline pressure.Results: A significant elevation of the IOP and a significant reduction in the ocular perfusion pressure (OPP) were found after applying the ophthalmodynamometer (both, P<0.001). The blowout score (BOS) (P<0.001) was significantly reduced, and the flow acceleration index (FAI; P<0.01) and resistivity index (RI; P<0.001) was significantly increased immediately after increasing the IOP by 20 or 30 mmHg (Experiment 1). During the IOP elevation throughout the 10 min, the BOS and the RI significantly recovered to the baseline at time 10 compared to time 0, (P <0.001 and P = 0.008, respectively) (Experiment 2).Conclusions: Our results indicate that the blood flow on the ONH is autoregulated by several mechanisms for changes in the OPP induced by an elevation of the IOP in normal subjects.

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Evaluation of optic nerve head blood flow in response to increase of intraocular pressure

Cited by 19 publications

References 42 publications

Acute Effects of Intraocular Pressure-Induced Changes in Schlemm's Canal Morphology on Outflow Facility in Healthy Human Eyes

Acute Effects of Intraocular Pressure-Induced Changes in Schlemm's Canal Morphology on Outflow Facility in Healthy Human Eyes

Changes in pulse waveforms in response to intraocular pressure elevation determined by laser speckle flowgraphy in healthy subjects

Changes in Pulse Waveforms in Response to Intraocular Pressure Elevation Determined by Laser Speckle Flowgraphy in Healthy Subjects

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