| 1. |
- Eklund, Anders, et al.
(författare)
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Evaluation of applanation resonator sensors for intra-ocular pressure measurement : results from clinical and in vitro studies.
- 2003
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Ingår i: Medical and Biological Engineering and Computing. - 0140-0118 .- 1741-0444. ; 41:2, s. 190-197
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Tidskriftsartikel (refereegranskat)abstract
- Glaucoma is an eye disease that, in its most common form, is characterised by high intra-ocular pressure (IOP), reduced visual field and optic nerve damage. For diagnostic purposes and for follow-up after treatment, it is important to have simple and reliable methods for measuring IOP. Recently, an applanation resonator sensor (ARS) for measuring IOP was introduced and evaluated using an in vitro pig-eye model. In the present study, the first clinical evaluation of the same probe has been carried out, with experiments in vivo on human eyes. There was a low but significant correlation between IOP(ARS) and the IOP measured with a Goldmann applanation tonometer (r = 0.40, p = 0.001, n = 72). However, off-centre positioning of the sensor against the cornea caused a non-negligible source of error. The sensor probe was redesigned to have a spherical, instead of flat, contact surface against the eye and was evaluated in the in vitro model. The new probe showed reduced sensitivity to off-centre positioning, with a decrease in relative deviation from 89% to 11% (1 mm radius). For normalised data, linear regression between IOP(ARS) and direct IOP measurement in the vitreous chamber showed a correlation of r = 0.97 (p < 0.001, n = 108) and a standard deviation for the residuals of SD < or = 2.18 mm Hg (n = 108). It was concluded that a spherical contact surface should be preferred and that further development towards a clinical instrument should focus on probe design and signal analysis.
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| 2. |
- Hallberg, Per, et al.
(författare)
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Applanation resonance tonometry for intraocular pressure in humans
- 2004
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Ingår i: Physiological Measurement. - : IOP Publishing. - 0967-3334 .- 1361-6579. ; 25:4, s. 1053-1065
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Tidskriftsartikel (refereegranskat)abstract
- Glaucoma is a group of diseases associated with optic nerve damage and loss of visual field. The aetiology is not completely understood, but one of the major risk factors is elevated intraocular pressure (IOP). Reliable methods for measuring the IOP are therefore important. The aim of the study was to investigate the ability of the applanation resonance tonometry (ART) system, based on continuous force and area recording, to measure IOP in humans. Both the phase of initial indentation (IOPIndentation) and the phase when the sensor was removed (IOPRemoval) from the cornea were analysed. The Goldmann applanation tonometry (GAT) was used as reference method. The study included 24 healthy volunteers with normal IOP and 24 patients with elevated IOP. The correlation and standard deviation (SD) between IOPIndentation and IOPGAT was R = 0.92 (p < 0.001), SD = 3.6 mmHg, n = 104, and between IOPRemoval and IOPGAT R = 0.94 (p < 0.001), SD = 3.1 mmHg, n = 104. In conclusion, resonance sensor technology has made it possible to introduce a new multi-point method for measuring IOP, and the method is relevant for measuring IOP in humans. The study indicates that with further development towards elimination of position dependence, the ART has the potential to become a useful clinical instrument for IOP measurement.
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| 3. |
- Lindahl, R, et al.
(författare)
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Determination of morpholine in air by derivatisation with 1-naphthylisothiocyanate and HPLC analysis
- 2001
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Ingår i: The Analyst. - : Royal Society of Chemistry. - 0003-2654 .- 1364-5528. ; 126:2, s. 152-154
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Tidskriftsartikel (refereegranskat)abstract
- A method for the determination of morpholine in air was developed. Samples were collected with adsorbent tubes containing XAD-2 resin coated with 1-naphthylisothiocyanate (NIT). The thiourea derivative formed was subsequently desorbed with acetonitrile and analysed by HPLC with UV detection. The recovery after gas phase spiking with morpholine (2.2-1570 micrograms) was 91% (86-100%) with a relative standard deviation of 5.5%. No effect on recovery from relative humidity or amount of morpholine was seen. The lowest level tested corresponded to 7 mg m-3 (1/10 threshold limit value) for a 15 min sampling period with a sampling rate of 20 ml min-1. Exposed NIT-coated XAD-2 tubes were stable at room temperature for at least 2 weeks.
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