Manometric measurement of the outflow facility in the living human eye and its dependence on intraocular pressure

Karyotakis, Nikolaos; Ginis, Harilaos; Dastiridou, Anna; Tsilimbaris, Miltiadis K.; Pallikaris, Ioannis G.

doi:10.1111/aos.12652

Cited by 23 publications

(33 citation statements)

References 30 publications

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“…This coefficient therefore may have been slightly overestimated. Although our estimate was somewhat higher than that reported for living eyes by Friedenwald 11 (0.021 μL −1 ) and Dastiridou et al 5,30 (0.022 μL −1 ), it was similar to that of Karyotakis et al (0.028 μL −1 ), 29 who used a manometric technique to determine the ocular rigidity coefficient.…”

Section: Discussionsupporting

confidence: 56%

“…The mean ocular rigidity coefficient was 0.0126 μL −1 with their method. Karyotakis et al 29 and Dastiridou et al 5,30 used the same manometric method and fitted an exponential curve to the pressure-volume relationship over a range of IOP from 15 to 40 mm Hg. The mean ocular rigidity coefficients were 0.028 μL −1 and 0.022 μL, −1 respectively.…”

Section: Discussionmentioning

confidence: 99%

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Comparison of Aqueous Outflow Facility Measurement by Pneumatonography and Digital Schiøtz Tonography

Kazemi

McLaren

Lin

et al. 2017

Invest. Ophthalmol. Vis. Sci.

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PurposeIt is not known if outflow facilities measured by pneumatonography and Schiøtz tonography are interchangeable. In this study we compared outflow facility measured by pneumatonography to outflow facility measured by digital Schiøtz tonography.MethodsFifty-six eyes from 28 healthy participants, ages 41 to 68 years, were included. Intraocular pressure (IOP) was measured in the sitting and supine positions with a pneumatonometer. With the subject in the supine position, IOP was recorded for 2 minutes by using a pneumatonometer with a 10-g weight and for 4 minutes by using a custom digital Schiøtz tonometer. Outflow facility was determined from the changes in pressure and intraocular volume and a standard assumed ocular rigidity coefficient for each instrument, respectively, and by using an ocular rigidity coefficient calculated by measuring pressure without and with a weight added to the pneumatonometer tip.ResultsThe outflow facility was 0.29 ± 0.09 μL/min/mm Hg by Schiøtz tonography and 0.24 ± 0.08 μL/min/mm Hg by pneumatonography (P < 0.001) when using the standard assumed constant ocular rigidity coefficient. Mean calculated ocular rigidity coefficient was 0.028 ± 0.01 μL−1, and outflow facility determined by using this coefficient was 0.23 ± 0.08 μL/min/mm Hg by Schiøtz tonography and 0.21 ± 0.07 μL/min/mm Hg by pneumatonography (P = 0.003). Outflow facilities measured by the two devices were correlated when the ocular rigidity was assumed (r = 0.60, P < 0.001) or calculated (r = 0.70, P < 0.001).ConclusionsOutflow facilities measured by pneumatonography were correlated with those measured by Schiøtz tonography, but Schiøtz tonography reported approximately 10% to 20% higher facilities when using the standard method. When ocular rigidity was determined for each eye, differences were smaller. Measurements from these devices cannot be compared directly.

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Section: Discussionsupporting

confidence: 56%

Section: Discussionmentioning

confidence: 99%

Comparison of Aqueous Outflow Facility Measurement by Pneumatonography and Digital Schiøtz Tonography

Kazemi

McLaren

Lin

et al. 2017

Invest. Ophthalmol. Vis. Sci.

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“…When the IOP reached 40 mmHg, the infusion stopped, and the sensor continuously recorded the decreasing IOP for a period of 4 minutes. The relationship between IOP increase and infused volume was used to calculate the ocular rigidity coefficient [ 17 ] while the IOP decay during outflow was used to calculate the outflow facility coefficient [ 18 ].…”

Section: Methodsmentioning

confidence: 99%

“…Ocular rigidity depends on the architecture and material properties of the eye globe. Measurements of OR have mainly been performed by means of paired Schiotz tonometry [ 12 ] or invasive manometric devices [ 13 – 18 ]. These measurements pertain to the injection (or displacement) of a given volume in the eye and measurement of the associated intraocular pressure change.…”

Section: Introductionmentioning

confidence: 99%

Ocular Rigidity and Outflow Facility in Nonproliferative Diabetic Retinopathy

Panagiotoglou

Tsilimbaris

Ginis

et al. 2015

Journal of Diabetes Research

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Purpose. To compare ocular rigidity (OR) and outflow facility (C) in patients with nonproliferative diabetic retinopathy (NPDR) and control subjects. Methods. Twenty-four patients with NPDR (NPDR group) and 24 controls (control group) undergoing cataract surgery were enrolled. NPDR group was further divided into patients with mild NPDR (NPDR1-group) and patients with moderate and/or severe NPDR (NPDR2-group). After cannulation of the anterior chamber, a computer-controlled device was used to infuse saline and increase the intraocular pressure (IOP) in a stepping procedure from 15 to 40 mmHg. Ocular rigidity and outflow facility coefficients were estimated from IOP and volume recordings. Results. Ocular rigidity was 0.0205 μL−1 in NPDR group and 0.0202 μL−1 in control group (P = 0.942). In NPDR1-group, OR was 0.017 μL−1 and in NPDR2-group it was 0.025 μL−1 (P = 0.192). Outflow facility was 0.120 μL/min/mmHg in NPDR-group compared to 0.153 μL/min/mmHg in the control group at an IOP of 35 mmHg (P = 0.151). There was no difference in C between NPDR1-group and NPDR2-group (P = 0.709). Conclusions. No statistically significant differences in ocular rigidity and outflow facility could be documented between diabetic patients and controls. No difference in OR and C was detected between mild NPDR and severe NPDR.

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“…Recently, there has been a shift to elastography approaches to study the biochemical properties of ocular tissues with either OCT [127] or with ultrasound [128], the visualization of biochemical properties of the eye coats in vivo would otherwise be incredibly challenging This perspective is propelled by several studies proposing the measurement of ocular rigidity using noninvasive measures instead [129,130]. However, none of these studies have addressed or included patients with myopia.…”

Section: Future Developmentsmentioning

confidence: 99%