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Yvonne I. Chu, Christopher C. Shen, Michael D. Straiko, Crawford Downs, Neda Shamie, Stuart K. Gardiner, Steven L. Mansberger; Assessment of Intraocular Pressure in Eyes with Keratoprosthesis. Invest. Ophthalmol. Vis. Sci. 2011;52(14):669.
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© ARVO (1962-2015); The Authors (2016-present)
To determine if current tonometry devices can obtain accurate, reliable, and reproducible intraocular pressure (IOP) measurements in eyes with Keratoprothesis.
We connected a digital manometer (XP2I Digital Test Gauge, Crystal Engineering, San Luis Obispo, CA) to a 27 gauge cannula and placed the cannula in the anterior chamber of human cadaver-eye. A single surgeon sutured the Boston Type I Keratoprothesis with 8.5 mm back plate into the central cornea. We used a Schiotz tonometer (Sklar, New York, NY) with a 7.5 gram plunger load and a Tono-pen XL tonometer (Medtronic, Jacksonville, FL) to determine IOP at the temporal corneoscleral limbus and temporal sclera (3mm posterior to the limbus) with the manometer set at 10, 20, 30, and 40 mm Hg. We determined precision and accuracy of each device at each specified anatomic site. We used Generalized Estimation Equation (GEE) models to determine an average absolute difference between the Schiotz tonometer compared to the manometric IOP and the Tono-pen XL tonometer compared to the manometric IOP.
The average (+/- SD) absolute difference at the temporal sclera between the Schiotz tonometer compared to the manometric IOP was 7.3 mm Hg (+/- 6.8), and with the Tono-pen XL tonometer was 35.2 mm Hg (+/- 16.3), (p-value<0.001). The average (+/- SD) absolute difference measured at the corneoscleral limbus with the Schiotz tonometer compared to the manometric IOP was 7.9 mm Hg (+/- 7.3), and with the Tono-pen XL tonometer was 16.5 mm Hg (+/- 15.3), p-value=0.184).
The Schiotz tonometer demonstrated a higher degree of accuracy and precision compared to the Tono-pen tonometer for measuring IOP at both the corneoscleral limbus and temporal sclera in eyes with Keratoprosthesis. On average, the Schiotz tonometer measured higher than the true manometric IOP at the sclera and lower than the true manometric IOP at the corneoscleral limbus for these eyes.
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