What portion of the orbit should the upper eyelid cover?

The upper eyelid typically covers approximately two-thirds of the visible portion of the eyeball when the eye is in a neutral position. This coverage is essential for protecting the eye and maintaining moisture. The eyelid plays a crucial role not only in protecting the eye from environmental factors and foreign objects but also in facilitating the tearing process to keep the surface of the eye lubricated. This anatomical positioning is a standard reference in both anatomical studies and practical applications in fields such as mortuary science, as understanding the proportions of facial features is critical for restorative arts and the presentation of deceased individuals. The coverage of two-thirds helps ensure the eye maintains its natural appearance, which is particularly important in cases where the deceased may require restorative work to present them as lifelike as possible.