Abstract
Purpose::
The aim of the study was to examine how ocular pulse amplitudes (OPA) are affected by acute changes of IOP.
Methods::
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.
Results::
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.
Conclusions::
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.
Keywords: intraocular pressure • choroid