Estimation of Ocular Rigidity Based on Measurement of Pulse Amplitude Using Pneumotonometry and Fundus Pulse Using Laser Interferometry in Glaucoma

Hommer, Anton; Fuchsjäger-Mayrl, Gabriele; Resch, Hemma; Vass, Clemens; Garhöfer, Gerhard; Schmetterer, Leopold

doi:10.1167/iovs.07-1342

Cited by 107 publications

(105 citation statements)

References 39 publications

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“…18,42 A growing body of research has shown that the sclera becomes stiffer in glaucoma. 7,43,44 These latter findings would support a link between myofibroblast-mediated detrimental sclera remodeling and mechanical damage to the ONH.…”

Section: Discussionmentioning

confidence: 73%

High-Magnitude and/or High-Frequency Mechanical Strain Promotes Peripapillary Scleral Myofibroblast Differentiation

Zhu

Ambalavanan

et al. 2015

Invest. Ophthalmol. Vis. Sci.

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PURPOSE.To determine the effects of altered mechanical strain on human peripapillary scleral (ppSc) fibroblast-to-myofibroblast differentiation.METHODS. Eight human ppSc fibroblast cultures were isolated from three paired eyes and two unilateral eyes of five donors using an explant approach. Human ppSc fibroblast isolates were subjected to 1% and 4% cyclic strain at 0.05 to 5 Hz for 24 hours. Levels of a smooth muscle actin (aSMA) mRNA and protein were determined by real-time PCR and immunoblot. Incorporation of aSMA into actin stress fibers was evaluated by confocal immunofluorescent microscopy. Myofibroblast contractility was measured by fibroblast-populated three-dimensional collagen gel contraction assay and phosphorylation of myosin light chain (MLC 20 ).RESULTS. Human ppSc fibroblasts contained 6% to 47% fully differentiated myofibroblasts before strain application; 4% cyclic strain increased aSMA mRNA and protein expression in ppSc fibroblasts compared with 1% strain applied at 5 Hz, but not at lower frequencies. Seven of eight ppSc fibroblast isolates responded to high-magnitude and high-frequency strain with increased cellular contractility and increased MLC 20 phosphorylation. In addition, increasing strain frequency promoted aSMA expression in ppSc fibroblasts under both 1% and 4% strain conditions.CONCLUSIONS. High-magnitude and/or high-frequency mechanical strain promotes differentiation of human ppSc fibroblasts into contractile myofibroblasts, a fibroblast phenotypic change known to be key to tissue injury-repair responses. These findings suggest that the cellular constituent of ppSc may play an important role in the regulation of optic nerve head biomechanics in response to injurious IOP fluctuations.

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Section: Discussionmentioning

confidence: 73%

High-Magnitude and/or High-Frequency Mechanical Strain Promotes Peripapillary Scleral Myofibroblast Differentiation

Zhu

Ambalavanan

et al. 2015

Invest. Ophthalmol. Vis. Sci.

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“…Assuming that FPA is proportional to the choroidal volume change during the cardiac cycle, PV (as assessed with pneumotonometry) and choroidal volume change (as calculated from FPA) should be equal. However, the ratio of choroidal volume change to PV may depend on two additional factors: ocular volume and ocular rigidity (Hommer et al 2008).…”

Section: Pcimentioning

confidence: 99%

A study comparing ocular pressure pulse and ocular fundus pulse in dependence of axial eye length and ocular volume

Berisha

Findl

Lasta

et al. 2010

Acta Ophthalmologica

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ABSTRACT.Purpose: There is a long-standing discussion about whether myopia is associated with decreased choroidal blood flow, as suggested by pneumotonometric measurements of pulsatile ocular blood flow (POBF). However, it has been noted previously that calculations of POBF depend on intraocular volume. Methods: In the present study we investigated this volume dependence through the comparison of ocular pressure pulse and ocular fundus pulse. Fifty-one healthy participants with different refractive errors participated in the study. Pulse amplitude (PA) and POBF were measured using pneumotonometry. Fundus pulsation amplitude (FPA) was measured with laser interferometry. Axial eye length (AEL) was measured with partial coherence interferometry. A mathematical model was used to calculate choroidal volume changes based on FPA. The ocular pressure pulse was converted into pulse volume (PV) according to the standard procedure used for pneumotonometry. Results: PA and POBF were found to decrease with increasing axial length (r = )0.55, p < 0.001 and r = )0.57, p < 0.001, respectively). A similar relationship existed for PV (r = )0.57, p < 0.001) and FPA (r = )0.46, p = 0.001). In addition, there was a significant association between PV and choroidal volume change during the cardiac cycle (r = 0.61, p < 0.001). Conclusion: The present study confirms experimentally that PA, FPA and POBF are dependent on ocular volume and indicates that the pulsatile component of ocular blood flow is not reduced in myopic patients. Accordingly, the relationship between AEL and POBF described previously appears to be a consequence of different ocular volumes. Our findings have important implications for studies using PA or POBF.

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“…25 Functional MRI, however, has a temporal resolution on the order of 10 seconds. Precision pneumotonometry, 26 combined with detection of fundus pulsation amplitude using laser interferometry, 27 provides a means for estimating overall ocular stiffness, but cannot distinguish the contribution of any particular layer or position. While a recent study described use of ultrasound to investigate the elastic properties of the retina and choroid by measurement of thickness changes of these layers with compression of the eye, 28 this approach differs fundamentally from the technique described here, since ARFI detects the dynamic effects of transient compression rather than the effects induced by static loading.…”

Section: Discussionmentioning

confidence: 99%

Effect of Ultrasound Radiation Force on the Choroid

Silverman

Urs

Lloyd

2013

Invest. Ophthalmol. Vis. Sci.

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PURPOSE. While visualization of the retina and choroid has made great progress, functional imaging techniques have been lacking. Our aim was to utilize acoustic radiation force impulse (ARFI) response to probe functional properties of these tissues. METHODS.A single element 18-MHz ultrasound transducer was focused upon the retina of the rabbit eye. The procedure was performed with the eye proptosed and with the eye seated normally in the orbit. The transducer was excited to emit ARFI over a 10-ms period with a 25% duty cycle. Phase resolved pulse/echo data were acquired before, during, and following ARFI.RESULTS. In the proptosed eye, ARFI exposure produced tissue displacements ranging from 0 to 10 lm, and an immediate increase in choroidal echo amplitude to over 6 dB, decaying to baseline after about 1 second. In the normally seated eye, ultrasound phase shifts consistent with flow were observed in the choroid, but enhanced backscatter following ARFI rarely occurred. ARFI-induced displacements of about 10 lm were observed at the choroidal margins. Larger displacements occurred within the choroid and in orbital tissues.CONCLUSIONS. We hypothesize that elevated intraocular pressure occurring during proptosis induced choroidal ischemia and that acoustic radiation force produced a transient local decompression and reperfusion. With the eye normally seated, choroidal flow was observed and little alteration in backscatter resulted from exposure. Clinical application of this technique may provide new insights into diseases characterized by altered choroidal hemodynamics, including maculopathies, diabetic retinopathy, and glaucoma. (Invest Ophthalmol Vis

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Estimation of Ocular Rigidity Based on Measurement of Pulse Amplitude Using Pneumotonometry and Fundus Pulse Using Laser Interferometry in Glaucoma

Abstract: The present study indicates increased ocular rigidity in patients with POAG. This is compatible with a number of previous animal experiments and supports the concepts that the biomechanical properties of ocular tissues play a role in the diseases process.

Cited by 107 publications

References 39 publications

High-Magnitude and/or High-Frequency Mechanical Strain Promotes Peripapillary Scleral Myofibroblast Differentiation

High-Magnitude and/or High-Frequency Mechanical Strain Promotes Peripapillary Scleral Myofibroblast Differentiation

A study comparing ocular pressure pulse and ocular fundus pulse in dependence of axial eye length and ocular volume

Effect of Ultrasound Radiation Force on the Choroid

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