Indirect, diffuse illumination may be employed, rather than direct illumination of the retina through the pupil. For indirect illumination, a cool-to-the-touch light source is pressed against the skin near the eye (e.g. against the skin on or adjacent to the eyelid). For example, the light source may be pressed against the skin adjacent to the lateral or medial canthus. The light passes through the skin, other tissues, sclera and choroid to provide diffuse, indirect illumination of the retina. Advantageously, this frees the pupil to be used solely for imaging (rather than for both illumination and imaging). The light source may comprise, for example, one or more light emitting diodes (LEDs).
© 2020 M. Everett Lawson.