Evaluating spatial dependency of spectral ‎efficiency in trans-palpebral illumination for ‎widefield fundus photography ‎

Multi-spectral widefield fundus photography is valuable for the clinical diagnosis and ‎management of ocular conditions that may impact both central and peripheral regions of the ‎retina and choroid. Trans-palpebral illumination has been demonstrated as an alternative to ‎transpupillary illumination for widefield fundus photography without requiring pupil dilation. ‎However, spectral efficiency can be complicated due to the spatial variance of the light ‎property through the palpebra and sclera. This study aims to investigate the effect of light ‎delivery location on spectral efficiency in trans-palpebral illumination. Four narrow-band ‎light sources, covering both visible and infrared wavelengths, were used to evaluate spatial ‎dependency of spectral illumination efficiency. Comparative analysis indicated a significant ‎dependence of visible light efficiency on spatial location, while near infrared (NIR) light ‎efficiency is only slightly affected by the illumination location. This study confirmed the pars ‎plana as the optimal location for delivering visible light to achieve color imaging of the retina. ‎Conversely, spatial location is not critical for NIR light imaging of the choroid.‎