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A. K. Nugent, F. Vargas-Martín, I. Wong; The Impact of Diagnostic Instrument Illumination Systems in Measuring Intraocular Inflammation. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1529.
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To determine how the biomicroscope illumination system affects the grading of anterior chamber inflammation.
An artificial anterior chamber was designed to optically replicate a human anterior chamber and filled with five micron polystyrene beads suspended in ethanol. A high-definition video eyepiece camera recorded the moving beads. Using image processing software, we determined the average number of beads in a 1 x 1 mm field at varying widths of the slit beam.
The volume of light and number of beads observed increased significantly as the slit beam widened. Additionally, three separate biomicroscopes of identical make and model were found to produce different levels of luminance at the same aperture dial settings, influencing the number of beads observed, with the brighter biomicroscope yielding higher bead counts.
Ability to count beads and perhaps the ability to count inflammatory cells in an inflamed eye depend on a number of factors including the level of illumination and width of the slit beam. This study demonstrated that the brighter the illumination and the wider the beam, the more beads were observed. This illustrates the importance of standardizing biomicroscopy particularly where consecutive observations are used to make clinical decisions and in cases of multi-center clinical trials where clinical data are evaluated across different facilities.
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