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former term for blindness of unknown etiology; the "serena" suggested that the anterior segment of the eye was clear and tranquil, that there was no visible cause for the blindness, no corneal scar, no inflammation, no cataract. Thus, gutta serena became the code word for blindness due to some unfathomable posterior cause, some damage to retina, optic nerve, or brain. This was the name given to John Milton's blindness. With the opthalmoscope, in 1851, the diagnosis of gutta serena suddenly became old-fashioned and inadequate.