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B.M. Ishimoto, J. Dillon, A. Yoshida, F. Mori; FluorotronTM for Measuring Ocular Oxygen Tension . Invest. Ophthalmol. Vis. Sci. 2003;44(13):3620.
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Purpose: Measuring the concentration of oxygen in localized regions without penetrating the eye would provide a new dimension in the understanding of the eye in both healthy and diseased states. In this study, an instrument was developed for measuring oxygen concentrations at multiple locations along the optical axis by measuring the excited-state lifetime of a phosphorescent dye. Methods: The FluorotronTM Master scanning ocular fluorophotometer (OcuMetrics, Inc., Mountain View, CA) was used as the basis for the new instrument. The light source was replaced with a 400 nm LED which is pulsed for 51 µsec durations. Phosphoresence lifetime is measured with a photomultiplier tube by photon binning. The bin duration is adjustable from 200 nsec to 13.11 msec with 1024 bins. The instrument is controlled by an embedded microprocessor that is in turn controlled by a personal computer through its serial port. Initial testing was performed using Pd-meso-tetra (4-carboxyphenyl) porphyrin or Pd-meso-tetra sulfonatophenyl porphyrin (TPPS) as the phosphorescent probes. Results: In the presence of BSA and under argon, the decay of TPPS resulted in two lifetimes at .36 and 1.52 msec. Repetitive scans gave reproducibility within 10 percent. TPPS (10 microliters of a 1 mg/ml solution) was injected into both the aqueous and vitreous of a pig cadaver eye and the fluorescent decays were determined. Using the first lifetime it was determined that oxygen tension in the aqueous was ca 30 mmHg and that in the vitreous was ca 15 mmHg. These are within reasonable agreement with published results. Conclusions: The modified Fluorotron is a useful instrument for the study of oxygen tension in various compartments within the eye. Its main advantage is that, except for the initial injection of the probe, it is non-invasive.
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