What type of illumination should be used for photographing external eye structures?

Using diffuse illumination for photographing external eye structures is essential because it provides a more even and soft light that reduces glare and shadows. This type of illumination enhances the details of the ocular surface and surrounding structures without overwhelming brightness that can obscure finer features.

Direct illumination tends to create harsh shadows and strong reflections, which can make assessment and details difficult to discern. Reflected illumination may also introduce glare, further complicating the image quality. Filtered light could soften the illumination but may not achieve the evenness that diffuse lighting provides. Overall, diffuse illumination is preferred as it allows for a clearer and more comprehensive visual of the eye's external anatomy.