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Janet Lim, Genie Bang, Thasarat Vajaranant, Ahmad Aref, Maria Cortina, Jose De la Cruz; Limbal and Scleral Pneumatonometer versus Manometric Reading in Cadaver Eyes with Type 1 Boston Keratoprosthesis. Invest. Ophthalmol. Vis. Sci. 2013;54(15):3457.
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© ARVO (1962-2015); The Authors (2016-present)
The use of keratoprostheses (KPro) to restore vision in eyes with corneal opacities has become increasingly popular. However, since glaucoma remains a major visual limiting factor in many of these eyes, it is important to be able to accurately measure and follow intraocular pressure (IOP). In this study, we assessed the difference and correlation between manometric IOP and pneumatonometry measurements on the sclera and limbus in cadaver eyes with KPros.
Two cadaver eyes were acquired from the Illinois Eye-Bank, and a Type 1 Boston KPro was implanted. The manometric IOP was varied between 5 to 40 mm Hg (in 5 mm Hg increments), and the pneumatonometer was used to measure IOP in 4 quadrants; superotemporal (ST), inferotemporal (IT), inferonasal (IN), and superonasal (SN). For every 5 mm Hg increment in IOP, 4 measurements were taken at each quadrant at the scleral limbus (SL) and 4 measurements on the sclera, 2 mm away from the limbus (S2), yielding 60 data points at each area of the globe. Paired t-test and Pearson’s correlation were used for the analysis.
The difference between the measured IOP using pneumatonometry and manometric IOP (Table 1) was lowest in the SL ST measurement (2.0 ± 3.9 mm Hg) and highest in the S2 IN measurement (10.8 ± 6.0 mm Hg). When measurements between 5 to 25 mm Hg and 30 to 40 mm Hg were compared, there was a decrease in the standard deviation in the SL SN measurements (3.38 and 2.98, respectively, p=0.004). All other areas showed an increase in the standard deviation as the IOP was raised. The difference between measured IOP and manometric pressure readings were on average higher for S2 measurements than SL measurements (2.8 ± 5.0 mm Hg vs. 7.8 ± 5.5 mm Hg, p<0.001). Overall, there was good correlation (r) between the IOP and the SL and S2 measurements at every quadrant with the highest correlations superiorly (Table 1).
Pneumatonometer readings on the sclera and limbus consistently yielded higher values compared to manometric readings. The pneumatonometer readings on the limbus in the superior quadrants have the highest correlation, as well as the smallest standard deviation when compared to the manometric IOP. These findings suggest that pneumatonometer measurement on the superior limbus could be used to monitor IOP in eyes with a Kpros.
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