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G. M. Bang, M. A. Kapamajian, T. Vajaranant, J. de la Cruz; Corneal, Limbal and Scleral Pneumotonometry Compared to Manometric Intraocular Pressure Measurements in Human Cadaveric Eyes. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1501.
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© ARVO (1962-2015); The Authors (2016-present)
One of the difficulties in monitoring keratoprosthesis patients is measuring the intraocular pressure, and there is currently no standard method to measure pressure other than palpation. The purpose of this project is to determine whether scleral pneumotonometry can be used as a reliable measurement of intraocular pressure when the corneal pressure cannot be assessed.
Eye bank eyes were connected to a pressure transducer system. Manometric intraocular pressure was adjusted in 5mmHg increments from 10 to 50. At each increment, a Model 30 Classic Pneumatonometer was used to measure intraocular pressure (IOP) on the central cornea, at the limbus, and on the sclera 2 mm from the limbus in all 4 quadrants. 3 measurements were taken at each point. Data from all 4 quadrants at each manometric increment were averaged among limbal and scleral measurements.
At manometric IOP ≤25mmHg, the difference between corneal (K), limbal (L), and scleral (S) pneumotonometric IOP and manometric pressure averaged +1.75 ±9.5 (p<0.01), +2.70 ±2.44 (p<0.01), and +7.65 ±3.27 (p<0.01) respectively. The correlation coefficients for the L and S measurements compared to manometric pressure were 0.996 and 0.990, respectively. At manometric pressure ≥30 mmHg, the difference between K, L, and S pneumotonometric IOP and manometric pressure averaged -6.33 ±5.68 (p<0.01), -4.69 ±5.07 (p<0.01), and +1.91 ±6.19 (p<0.01) respectively. The correlation coefficient for the L and S measurements compared to manometric pressure were 0.933 and 0.760 respectively.
Preliminary data shows scleral pneumatonometry measures consistently higher than the corneal measurement, and correlates with manometric pressure (r =0.992 and 0.760 at manometric pressure ≤25 mmHg and ≥35 mmHg, respectively). Limbal pneumotonometry strongly correlated with manometric pressure (r = 0.996 and 0.933 at ≤25 mmHg and ≥30 mmHg, respectively). This linear relationship suggests that clinicians may be able to use scleral pneumatonometry to estimate IOP in eyes that may not normally be able to undergo objective corneal measurements.
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