Amaurosis is vision loss or weakness that occurs without an apparent lesion affecting the eye. It may result from either a medical condition or excess acceleration, as in flight. The term is the same as the Latin gutta serena, which means, in Latin, clear drop. Gutta serena is a condition of partial or complete blindness with a transparent, clear pupil. This term contrasts with suffusio nigra which means, in Latin, dark suffusion, indicating partial or complete blindness with a dark pupil, e.g., a cataract. Milton, already totally blind for twelve years by the time he published Paradise Lost, refers to these terms in Book 3, lines 25–26.