A Technique for Real-Time Overlap of a Reflection Image and an Autofluorescence Image Using cSLO

For age-related macular degeneration examination, imaging techniques of confocal scanning laser ophthalmoscopy (cSLO), indocyanine green angiography, and fluorescein angiography have been used for studying the fundus, but in a monochromatic manner. When an autofluorescence image is required to be added on a gray-scale reflection image, the software plays a key role to form the colored image. In this study, we develop a hardware plug-in device for traditional cSLO to upgrade it so that it will show an overlapped color image containing both the reflection and autofluorescence images. We only use the laser (488/514 nm) within cSLO to incorporate with the hardware image overlapping system (HIOS) developed herein to real-time detect and convert both the monochromatic reflection and autofluorescence signals into a colored image. A model-retina and fluorescein isothiocyanate (FITC) dye with different concentrations is painted on the “retina” to simulate the drusen in real retina. System validation and sensitivity are evaluated by examining the “retina” image, while the observance of fluorescence results from various concentrations of FITC. The reflection and autofluorescence images are successfully separated by the optic system, further overlapped through the HIOS, and real-time displayed on a color monitor. The system sensitivity to detect fluorescence of FITC is as low as 5 × 10⁻¹⁰ mol. The results of this study suggest that this type of hardware add-on technology can help upgradation of traditional cSLO to the level of autofluorescence fundus imaging economically and with a broadening of the diagnostic capability of cSLO.