The effect of biomicroscope illumination system on grading anterior chamber inflammation

Abstract

Purpose: To determine how a biomicroscope illumination system affects the grading of anterior chamber (AC) inflammation.

Design: Laboratory investigation.

Methods: An artificial AC was designed to replicate optically a human AC and was filled with 5-mum polystyrene beads suspended in ethanol. A high-definition video eyepiece camera recorded the moving beads. Using image processing software, the main outcomes measures determined were the average number of beads in a 1 x 1-mm field at varying widths of the slit-beam.

Results: The volume of light and number of beads observed increased significantly as the slit-beam widened. Additionally, 3 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.

Conclusions: 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 multicenter clinical trials where clinical data are evaluated across different facilities.