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Youngcheol Yoo, Ka Young Lee; Accuracy and reliability of rebound tonometer to measure the IOP of enucleated pig eyes in vertical and horizontal positions. Invest. Ophthalmol. Vis. Sci. 2014;55(13):140.
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To evaluate the accuracy and the intraobserver repeatability of rebound tonometer to measure IOP of enucleated pig model eyes in vertical and horizontal positions.
We developed an enucleated experimental pig eye model whose anterior chamber was cannulated with a 30-gauge needle, which in turn was connected parallel to a pneumatic pressure device. Reference pressure was manipulated by changing the air pressure from 70 to 10mmHg at 10mmHg intervals, and the IOP of model eyes was measured with the rebound tonometer (Icare PRO; Icare Finland Oy, Helsinki, Finland) at each reference IOP level. Three valid IOP readings were recorded consecutively and averaged. Correlation analysis, comparison using the Bland-Altman plot and paired t-test was performed to assess the accuracy of IOP measurements. Intraclass correlation coefficient was calculated to assess the intraobserver variability.
The IOP values measured by the rebound tonometer in both vertical and horizontal positions were well correlated with the reference IOP (r=0.985 and 0.970, respectively). All IOP values measured in both positions were lower than the reference value and the higher reference pressure the more obvious differences. The IOP values measured in the horizontal position were significantly lower than those in the vertical position at the reference pressure of 50mmHg or more. Intraclass correlation coefficient showed the range from 0.802 to 0.947 in the horizontal position and from 0.506 to 0.744 in the vertical position.
The higher the reference IOP was set the IOP measurements by Icare PRO rebound tonometer were underestimated in both vertical and horizontal position. This trend was more pronounced in the horizontal position than in the vertical position. Also, the reliability of IOP measurements in the horizontal position was lower than that in the vertical position.
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