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F. Berisha, O. Findl, G. Fuchsaeger–Mayrl, L. Schmetterer; Dependence of ocular rigidity on eye length: a study comparing ocular pressure pulse and ocular fundus pulse in healthy subjects . Invest. Ophthalmol. Vis. Sci. 2004;45(13):2613.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:There is a long–standing discussion whether myopia is associated with decreased ocular rigidity. The purpose of this study was to investigate the relation of axial refraction to ocular rigidity by comparison of pneumotonometric and laser interferometric measurements. A mathematical model was used to calculate ocular rigidity by comparison of the volume and pressure change during the cardiac cycle. Methods:A total of 51 healthy subjects with different refractive errors participated in the study. Pulse amplitude (PA) of intraocular pressure (IOP) and pulsatile ocular blood flow (POBF) were measured using pneumotonometry. Fundus pulsation amplitude (FPA) measurements were obtained with laser interferometry. From this parameter the choroidal volume change during the cardiac cycle was calculated. Axial eye length (AEL) was measured with partial coherence interferometry. In the present study the ocular pressure pulse was converted into pulse volume (PV) according to the standard procedure used for pneumotonometry and the ratio between pulse volume and choroidal volume change was used to determine ocular rigidity. 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 the PV (r = – 0.57, p<0.001) and FPA (r = – 0.46, p=0.001). In addition, there was a significant association between the PV and choroidal volume change during the cardiac cycle (r = 0.61, p<0.001). Ocular rigidity, however, showed an inverse correlation with eye length (r = – 0.69, p<0.001, ANOVA). Conclusions:In conclusion, the present study indicates that a relationship exists between the AEL, PA, ocular PV and POBF. Myopic eyes were found to have a lower ocular rigidity than emmetropic and hyperopic eyes. Our findings have important implications for studies using the ocular pulse or POBF, for Schiotz tonometry and potentially for the understanding of the pathophysiology of myopia.
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