The phrase "eventual blindness" means that someone will gradually lose their ability to see and will become completely blind over time. Full definition
Miniature Schnauzers have several eye diseases (most hereditary) that can cause eventual blindness in the dog: Progressive Retinal Atrophy (PRA) causes slow, progressive blindness, while Sudden Acquired Retinal Degeneration (SARD) results in sudden blindness. (tcmsc.com)
A cat not getting enough taurine can end up with heart disease, eye problems (including eventual blindness,) dental problems and even hair loss. (best-cat-art.com)
Pembroke Welsh Corgis can be afflicted with several eye problems including, cataracts, Progressive Retinal Atrophy which causes eventual blindness, and Retinal Dysplasia, which causes abnormal development of the retina and can lead to blindness also. (wagbrag.com)