What term describes the condition where all ability to see is lost?

The term that describes the complete loss of the ability to see is "blindness." This is a definitive term used in both medical contexts and in everyday language to indicate a total lack of vision. Blindness can result from various causes, including congenital conditions, diseases, or traumatic injuries that severely affect the eye or the visual pathways in the brain.

While "low vision," "legal blindness," and "visual impairment" describe conditions related to reduced or limited vision, they do not convey the total inability to see. Low vision refers to significant visual impairment that cannot be corrected with standard glasses or lenses but still allows some sight. Legal blindness is a specific legal definition that often allows individuals to access services and benefits; it typically involves having a certain level of visual acuity or a specific field of vision (most commonly defined as visual acuity of 20/200 or less in the better eye). Visual impairment encompasses a broader range of vision loss, not limited to complete blindness.

Thus, the term "blindness" uniquely and specifically describes the complete loss of sight, making it the correct choice in this context.