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R. Asaoka, A. Kotecha, E. White, D. F. Garway-Heath; The Effects of Maximum Air Pulse Pressure and Intraocular Pressure on Corneal Hysteresis Measurements With the Reichert Ocular Response Analyser. Invest. Ophthalmol. Vis. Sci. 2008;49(13):703.
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© ARVO (1962-2015); The Authors (2016-present)
The aim of the study was to evaluate the effects of maximum air pulse pressure (Pmax) and decrease of intraocular pressure (IOP) by apraclonicine on corneal hysteresis (CH) measurements with the Reichert Ocular Response Analyser (ORA) in 20 normotensive and 20 ocular hypertensive subjects. In the current ORA, Pmax varies according to the IOP.
ORA measurements with three different Pmax units (500, 400, 300) and IOP measurements using Goldmann applanation tonometry (GAT) have been performed on 11 normal subjects (one eye per subject). Measurements were carried out at baseline (a), and then following the administration of apraclonidine (b - 30 minutes, c - 1 hour, d - 1.5 hours, e - 2.5 hours). The effects of Pmax and IOP on CH and corneal resistance factor (CRF) were recorded.
All GAT IOP measurements following aproclonidine (GATb: 12.7±2.6, mean ± standard deviation, GATc: 11.5±2.0, GATd: 10.3±3.6, and GATe: 10.0±2.0) were significantly lower than the baseline GAT IOP (GATa: 13.8±2.4). CH was significantly larger with higher Pmax values: CH500a (CH before apraclonidine administration with Pmax=500unit) was larger than CH400a and CH300a (pCH300b (p=0.0046), CH500c>CH400c (p=0.009), CH400c>CH300c (pCH400d (p=0.02), CH500e>CH400e (pCH300e (pCH300a (p=0.0099), CH500d>CH500a (p=0.03), CH500e>CH500a (p=0.007). CRF also tended to be larger with higher Pmax, while CRF tended to become smaller after apraclonidine administration.
These preliminary data suggest that the variation of Pmax with IOP may induce an artificial change in CH and CRF. When measuring corneal hysteresis, it may be beneficial to maintain uniform Pmax values. The IOP level affects CH values.
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