Background: The aim was to evaluate the effects of the Valsalva manoeuvre on Ocular Response Analyzer (ORA) measurements.
Methods: A total of 152 eyes of 76 healthy individuals were included. The biomechanical properties of cornea, including corneal hysteresis (CH), corneal resistance factor (CRF) and intraocular pressure (IOP) parameters, namely, cornea compensated IOP (IOPcc) and Goldmann correlated IOP (IOPg) as measured with ORA were obtained before and during the Valsalva manoeuvre. Wilcoxon test for group analysis, Mann-Whitney test for intergroup analysis, Generalized Estimating Equation, and Spearman's test for correlation analysis were used.
Results: The mean age of the 76 subjects (52 female) was 34.18 ± 10.20 years (range, 21 to 58 years). The mean IOPcc was 14.50 ± 0.30 mmHg before and 19.80 ± 0.60 mmHg during the Valsalva manoeuvre (p < 0.001). The mean IOPg before the Valsalva manoeuvre was 15.02 ± 0.33 mmHg and during was 20.18 ± 0.63 mmHg (p < 0.001). The mean corneal hysteresis was 11.40 ± 0.15 mmHg before Valsalva manoeuvre, and 10.60 ± 0.16 mmHg during Valsalva manoeuvre (p < 0.001). Pre-Valsalva manoeuvre mean corneal resistance factor was 11.97 ± 0.16 mmHg, whereas during the Valsalva manoeuvre, the mean corneal resistance factor was 12.06 ± 0.20 mmHg (p < 0.001). There was no correlation between age and either pre- or during-Valsalva manoeuvre measurements. The change in IOPcc and corneal hysteresis before and during Valsalva manoeuvre showed no intersexual difference; however, IOPg and corneal resistance factor change before and during Valsalva manoeuvre were significantly higher in male subjects. A negative correlation between pre-Valsalva manoeuvre corneal hysteresis and pre- and during-corneal resistance factor difference (r = -0.167) was detected.
Conclusions: Valsalva manoeuvre causes a statistically significant increment in IOPcc, IOPg and corneal resistance factor and statistically significant decrement in corneal hysteresis. For this reason, to obtain reliable results, ORA measurements should be performed in suitable positions and with clothes that do not increase thoracic or abdominal pressure.
Keywords: Ocular Response Analyzer; Valsalva manoeuvre; cornea; corneal hysteresis; corneal resistance factor; intraocular pressure.
© 2015 The Authors. Clinical and Experimental Optometry © 2015 Optometry Australia.