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A. G. Boehm, A. Weber, E. Spoerl, L. E. Pillunat; The Effect of Acute IOP Changes on Ocular Pulse Amplitudes Measured by Pascal Dynamic Contour Tonometry. Invest. Ophthalmol. Vis. Sci. 2007;48(13):4945.
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The aim of the study was to examine how ocular pulse amplitudes (OPA) are affected by acute changes of IOP.
In a prospective clinical trial 60 eyes of 60 patients (M:F=43:17; mean age 73.4±9.5y) undergoing phacoemulsification were examined. Before surgery the anterior chamber was cannulated at the temporal corneal limbus. In a closed system the IOP was directly set to 15, 20 and 35 mmHg by manometric water column. The different IOP levels were adjusted in a random sequence. Ocular pulse amplitudes were measured by DCT and intracamerally as a reference. At each IOP level 3 measurements were obtained. In addition parameters IOP, central corneal thickness (CCT), corneal curvature, axial length (AL), age, and sex were evaluated and analyzed in an univariate regression analysis.
OPA measured by DCT was 1.19±0.41mmHg at the IOP level of 15mmHg, 1.55±0.57mmHg at 20mmHg and 2.11±0.71mmHg, respectively. Differences between the IOP levels were statistically significant P<0.001. An IOP change of 10mmHg resulted in an OPA change of 0.044mmHg. Univariate regression analysis showed a statistically positive correlation of OPA with IOP, CCT, corneal curvature, and age, and a negative correlation with AL. Females had lower OPAs than males. Bland-Altman analysis showed a good agreement of intracameral OPA measurements with OPA taken by DCT.
An isolated increase of IOP leads to a significant increase of OPA. Additionally, OPA is affected by other parameters, e.g. CCT, corneal curvature, AL, age, and sex suggesting that factors connected with a stiffness increase of the wall of the eye globe lead to an increase of OPA.
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