Optimising Visualisation of Fluorescein Dye

Purpose: The use of the excitation and emission filters in conjunction with sodium fluorescein dye to examine the anterior eye have not been studied when considering different light sources. This is despite the industry now incorporating white LED lights in slit lamps used in eye examinations in place of halogen light. Novel, cost-effective filter combinations that minimise spectral overlap are proposed, enhancing the contrast of fluorescein dye compared with traditionally used filters. Methods: The Oceanview spectrophotometer recorded the spectral distribution and intensity of light traveling through an emission and excitation filter. Several combinations of emission filter, excitation filter and light source were trailed. Following this, 50-micron aliquots of diluted fluorescein against a background were photographed for various filter combinations. Contrast was defined as the minimum visible thickness of fluorescein divided by the background illumination. Results: The combination of white LED light, the BG3 excitation filter, and Wratten No. 12 emission filter showed superior contrast when compared to similar combinations involving the Haag Streit cobalt blue excitation filter. These results did not hold for filter combinations involving halogen light. Discussion: Previous filters mentioned in the literature are no longer available, leaving either costly matched interference filters, or the traditional Wratten 12/cobalt blue filters to view the anterior eye through the slit lamp. The latter combination may produce “optical noise” and reduce image contrast. White LED light, combined with the BG3 excitation filter, and the Wratten No. 12 emission filter show relative improvements in contrast when compared with traditionally used filter combinations. Conclusions: The superior contrast is exhibited by the BG3 filter when used in combination with the Wratten No. 12 Emission filter and white LED light sources may provide stimulus for further research into its clinical use in eye exams