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M. Pease, J.C. Hammond, J.L. Kielczewski, H.A. Quigley; TonoLab Is Superior to TonoPen in Measurement of Intraocular Pressure in Rat and Mouse Eyes . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1251.
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© ARVO (1962-2015); The Authors (2016-present)
: To compare the TonoPen and the TonoLab instruments in normal and experimental glaucoma rats and to calibrate the TonoLab tonometer for the first time in living mouse eyes.
In 21 normal rats and 16 rats with either 2 or 4 week experimental glaucoma, manometrically set intraocular pressure (IOP) was compared to that measured by the TonoLab under open stopcock conditions. Of these, 7 normal and 7 glaucoma eyes were measured in both the open and closed stopcock condition. For comparison, an additional 10 normal rats were measured by TonoPen under open stopcock conditions. In 20 rats, IOP was measured one day after laser treatment in uncannulated eyes by both TonoLab and TonoPen, alternating which device was used first. The number of applications to acquire a complete data set was recorded in a subset of animals for both instruments. Lastly, TonoLab readings were compared to manometeric IOP in 10 mice under open stopcock conditions.
: Compared to manometric IOP, the TonoPen underestimated every IOP >20 mm Hg (7 mm Hg underestimate at 50 mm Hg), while the TonoLab was within 1 mm Hg of manometry at all levels in both normal and glaucoma rats (TonoPen regression: y = 0.82x + 3.29 (R2 = 0.96), TonoLab regression: y = 0.99x–0.91 (R2 = 0.98) for normal eyes, y = 0.99x – 0.62 (R2 = 0.98) for glaucoma eyes). Under closed stopcock conditions, the TonoLab slightly under read the IOP in both normal and glaucoma eyes (TonoLab regression: y = 0.85x+1.21 (R2 = 0.93) for normal eyes, y = 0.94x – 0.44 (R2 = 0.95) for glaucoma eyes). TonoLab readings in mice also compared favorably to manometric IOP (TonoLab regression: y = 0.97x + 1.57 (R2 = 0.98). For uncannulated glaucoma eyes, the instrument used first reported higher IOP (p = 0.015, TonoLab first; p = 0.005, TonoPen first). The mean difference in paired readings on glaucoma eyes was greater when the TonoPen was used first (5 mm Hg) compared to when the TonoLab was used first (3.9 mm Hg), but the difference was not significant (p = 0.6). The mean number of applications of the tonometer to the eye to achieve a single reading was 11.9 for the TonoPen and 1.1 for the TonoLab.
TonoLab more closely matches manometric IOP than TonoPen in rats. TonoPen causes more IOP reduction during measurement, in part due to excessive numbers of applications to achieve readings. TonoLab measurements in mice are accurate and clearly preferable to invasive methods.
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