The phrase "visible signs" refers to things that can be seen or observed easily. It indicates that there are clear indications or evidence that can be noticed with the naked eye. Full definition
Some formulas can help reduce the appearance of visible signs of aging — think: fine lines and wrinkles — and plump the appearance of the skin so it appears more youthful. (skincare.com)
A shiny, radiant coat is the most visible sign of a healthy diet. (eukanuba.com)
Keep in mind, that even if a dog is not showing visible signs of the disease, if infected, damage is still occurring in the blood vessels, heart, and lungs. (schnauzers-rule.com)