Abstract
Purpose: :
To measure the intraocular pressure (IOP) with two different tonometers and to compare their accuracy and reliability when evaluating the pressure in the rabbit eye.
Methods: :
The IOPs of 8 freshly enucleated eyes from White New Zealand rabbits were measured with a pressure transducer that was connected to the anterior chamber of the eyes. The IOP was varied by changing the height of a bottle filled with a saline solution (PBS 1x). Intraocular pressures were recorded over a range of 50 to 5 mmHg by the transducer system and comparative measurements at the same pressures were performed with both the Tonopen XL and the rebound iCARE Tonovet tonometers. Accuracy was defined as the difference between the tonometer and transducer measurements. Variation in measurement error at the different IOPs and linear regression analysis were used to assess the reliability of each instrument.
Results: :
IOP was set at 10, 20, 30, 40 and 50 mmHg and tonometer measurement gave following results: 5.08 ± 0.55, 11.25 ± 1.03, 17.54 ± 1.78, 24.75 ± 1.61, 33 ± 2.21 mmHg for the Toponen XL, and 6.62 ± 0.57, 15.41 ± 1.38, 23.83 ± 0.9, 33 ± 1.38, 41.83 ± 2.12 mmHg for the iCARE Tonovet, respectively. The differences between the reference pressure (transducer) and tonometers readings were statistically significant (p<0.0001 for the Tonopen XL and p<0.0001 for the iCARE Tonovet). Variation and gradient of regression lines (m) were 27.33 mmHg and -0.34 for the Tonopen XL; 5.24 mmHg and -0.13 for the iCARE Tonovet, respectively.
Conclusions: :
The IOP was consistently underestimated using either Tonopen XL and iCARE Tonovet. The inaccuracy was increasing at higher pressures for both tonometers. Nevertheless the rebound iCARE Tonovet tonometer gave the most reliable data in measuring IOP in the range of 10 to 45 mmHg.
Keywords: intraocular pressure • anterior segment